7D always 1 to 1.5 overexposed.
- Thread starter Brocks
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Tim, not sure what you mean that the intermediate ISOs are fakes - surely ISO sensitivity as a whole is 'fake' anyway, as all you're doing is upping the gain on the sensor. Would you be able to explain in laymens terms to me how intermediate ISOs are any more fake than the full stop increments?
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The full stop ISOs are generated using an analogue amplifier to boost the signal, a bit like an aerial booster might for your TV. But that amplifier is only designed to have "gain" settings that hit the full stops. In order to get an ISO such as 125, 250, 500 and so on the analogue gain used within the camera will only get you as far as 100, 200, 400, etc.. All that happens within the camera to make the image 1/3 stop brighter is a mathematical multiplication of each pixel brightness value by a factor of 5/4.
What that means is that the camera is doing a software boost of the exposure, much as you might do yourself in your raw editing software. Therefore this is not a "real" amplification of the signal. It is a mathematical fake. So what actually happens is that, for example, you think you are shooting at 500 ISO, but secretly the camera is only shooting at 400 ISO and underexposing your shot by 1/3 stop. The camera then covers up the underexposure with a little bit of mathematical massage. As with any underexposed image, the software boost may show a little more noise in the image. What is equally bad is that you may have a perfectly good base exposure but the exposure boost in camera may send your highlights into clipping, when the real exposure was not clipped at all.
In other words, any ISO 1/3 above a full stop ISO is an underexposed shot that might lead to more visible noise and/or might lead to highlight clipping. If you'd underexposed for yourself by sticking to 400 ISO you might end up with more noise, but at least you would have an extra 1/3 stop of highlight headroom to play with.
A similar thing happens when you shoot at 160, 320, 640, 1250 ISO and so on, except this time the camera shoots at the ISO above and then mathematically reduces the exposure by a factor of 5/4 to achieve the faked ISOs. This in camera exposure reduction may make noise less obvious, which people think is good (and I suppose it is) but bearing in mind the initial capture was originally 1/3 brighter, you may actually clip your highlights initially and then the camera will pull them down so you don't notice. You could blow crucial detail in that brightest 1/3 stop and simply not be aware until it was too late.
In my opinion it is better to make your own decisions about how high to push your luck with the exposure and then you decide what to do with the raw file in your raw software. Why have the camera muck about with the data and potentially FUBAR it before you get your hands on it? OK, it's only 1/3 stop we're talking about here, but if you seriously want to obtain the best image capture you can then 1/3 stop matters.
For much the same reasons I have equal distaste for HTP. It is an in camera underexposure by one full stop and then a sneaky patch up of the underexposed file within the camera, or DPP for raw files. If you shoot to JPEG I concede HTP may have some small merit. If you shoot to raw then it has no value that I can see. Anyone can make their own choice whether to underexpose by 1 stop, 2/3 stop 1/3 stop manually, and then can process the file as they wish later, knowing they are in full control of the original raw data and squeezing the best from it. But underexposure is a bad thing, so why do it at all, especially intentionally?
Don't even get me started on ALO. Fortunately it doesn't screw with raw data, but it can certainly lead to disappointing results in JPEG (and some very pleasing ones too), and won't do anything to help those who are trying to learn more about photography. Using ALO is a bit like saying to the camera - "You get on with it. You fix my files for me. I don't want to get involved." You won't learn a thing if you have ALO try to cover up your mistakes. It's like all those old negatives that had exposures all over the map, but the print lab sorted them out for you so you never knew how bad they really were.
Just my opinion.
p.s. the above holds true for all Canon cameras, as far as I know, except the 1 series bodies. The 1 series bodies (at least prior to the 1D4) have a two stage analogue amplifier, but I am given to understand that the second stage amplifier is not terribly good and effectively renders intermediate ISOs on the 1 series bodies also of questionable value. I don't know how true that is, but to keep the operation of all my bodies consistent I only use full stop ISOs on my 1D3.
I have no information on the behaviours of cameras from other manufacturers.
p.p.s. ISO 50 is also fake. The sensor cannot shoot at 50 ISO. It is just in camera mathematics that pulls the file down by one stop from 100. By then, if your scene contains highlights they might already be lost. You may just as well shoot at 100 ISO in the first place and take control of any clipping/overexposure yourself.
What that means is that the camera is doing a software boost of the exposure, much as you might do yourself in your raw editing software. Therefore this is not a "real" amplification of the signal. It is a mathematical fake. So what actually happens is that, for example, you think you are shooting at 500 ISO, but secretly the camera is only shooting at 400 ISO and underexposing your shot by 1/3 stop. The camera then covers up the underexposure with a little bit of mathematical massage. As with any underexposed image, the software boost may show a little more noise in the image. What is equally bad is that you may have a perfectly good base exposure but the exposure boost in camera may send your highlights into clipping, when the real exposure was not clipped at all.
In other words, any ISO 1/3 above a full stop ISO is an underexposed shot that might lead to more visible noise and/or might lead to highlight clipping. If you'd underexposed for yourself by sticking to 400 ISO you might end up with more noise, but at least you would have an extra 1/3 stop of highlight headroom to play with.
A similar thing happens when you shoot at 160, 320, 640, 1250 ISO and so on, except this time the camera shoots at the ISO above and then mathematically reduces the exposure by a factor of 5/4 to achieve the faked ISOs. This in camera exposure reduction may make noise less obvious, which people think is good (and I suppose it is) but bearing in mind the initial capture was originally 1/3 brighter, you may actually clip your highlights initially and then the camera will pull them down so you don't notice. You could blow crucial detail in that brightest 1/3 stop and simply not be aware until it was too late.
In my opinion it is better to make your own decisions about how high to push your luck with the exposure and then you decide what to do with the raw file in your raw software. Why have the camera muck about with the data and potentially FUBAR it before you get your hands on it? OK, it's only 1/3 stop we're talking about here, but if you seriously want to obtain the best image capture you can then 1/3 stop matters.
For much the same reasons I have equal distaste for HTP. It is an in camera underexposure by one full stop and then a sneaky patch up of the underexposed file within the camera, or DPP for raw files. If you shoot to JPEG I concede HTP may have some small merit. If you shoot to raw then it has no value that I can see. Anyone can make their own choice whether to underexpose by 1 stop, 2/3 stop 1/3 stop manually, and then can process the file as they wish later, knowing they are in full control of the original raw data and squeezing the best from it. But underexposure is a bad thing, so why do it at all, especially intentionally?
Don't even get me started on ALO. Fortunately it doesn't screw with raw data, but it can certainly lead to disappointing results in JPEG (and some very pleasing ones too), and won't do anything to help those who are trying to learn more about photography. Using ALO is a bit like saying to the camera - "You get on with it. You fix my files for me. I don't want to get involved." You won't learn a thing if you have ALO try to cover up your mistakes. It's like all those old negatives that had exposures all over the map, but the print lab sorted them out for you so you never knew how bad they really were.
Just my opinion.
p.s. the above holds true for all Canon cameras, as far as I know, except the 1 series bodies. The 1 series bodies (at least prior to the 1D4) have a two stage analogue amplifier, but I am given to understand that the second stage amplifier is not terribly good and effectively renders intermediate ISOs on the 1 series bodies also of questionable value. I don't know how true that is, but to keep the operation of all my bodies consistent I only use full stop ISOs on my 1D3.
I have no information on the behaviours of cameras from other manufacturers.
p.p.s. ISO 50 is also fake. The sensor cannot shoot at 50 ISO. It is just in camera mathematics that pulls the file down by one stop from 100. By then, if your scene contains highlights they might already be lost. You may just as well shoot at 100 ISO in the first place and take control of any clipping/overexposure yourself.
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That was one heck of an explanation, thanks a bunch for taking the time to write that out. Really helpful. I particularly enjoyed the paragraphs on ALO and HTP, particularly as I just recently turned them off in camera.
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top forumming Tim - very helpful indeed.
ta
ta
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Jerry, sorry, I think I overlooked your question and filed to reply. When shooting raw there is a very powerful technique called "Expose to the Right" or ETTR. It means you set your exposure so that the histogram is nudged over towards the right hand edge, as close to clipping as possible, without actually clipping anything important in the scene. Specular highlights and light sources (street lamps, for example) are an exception. By exposing in such a way you capture as much image DATA as possible, while keeping the image data as far as possible above the noise floor in the shadow region. Think about shooting raw as capturing DATA (after all, it is just bits and bytes, not an actual image), not about taking pictures. You don't need your exposure to be "correct". You want it to record as much DATA as possible. You will make it look nice later on.
If you underexpose and then boost the exposure in post you will also boost the noise in the shadows. If you expose as brightly as possible, then reduce the exposure in post to make it look good, you will also lower the shadow noise until it is even less visible.
This approach would be standard for most types of raw shooting. This is what I mean by "exposing for the highlights". You place them very precisely to maximise dynamic range. The downside is that in scenes of high dynamic range the shadows have to make do with ending up wherever they may, but at least you did your best.
However, if your subject and interest actually lies more in the shadow region, such as a black dog, then you would indeed expose for the shadows, but in so doing you may have to wave goodbye to some highlight details as a consequence, and may even blow the sky altogether, for example. So it is a bit of a juggling act but experience should help guide you to optimising the exposure for the subject specifically and the scene as a whole.
You can read more on the whys and wherefores of ETTR here....
http://www.luminous-landscape.com/tutorials/expose-right.shtml
and here....
http://ronbigelow.com/articles/exposure/exposure.htm
My technique of exposing my highlights at +3 on the meter means I can easily place my highlights at the right hand edge of the histogram. It is a reliable and effortless way to accomplish that aim instantly. By locking in my exposure manually I can then feel free to compose however I like, zooming in or out and waving my camera about with not a care in the world about what the meter sees and thinks from that point on. If I find my exposure just a little off then a single click left or right will have me sorted and good to go. This is far easier than having to adjust EC every time the subject or scene changes, even just a little.
I haven't read through it, but I think there may be some interesting stuff about the benefits of raw, here - http://ronbigelow.com/articles/raw/raw.htm.
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Firstly Tim, Id like to thank you for the time and effort you have put in to these posts lately. I know I am among many who have learned quite a lot more about exposure in general and the 7D in particular (in the bird forum)
I have just started to try manual metering on static bird shots but have up to now cheated byfor example, setting exposure on a tree trunk bathed in sunlight then waited for the bird (treecreeper) to, hopefully, pop along. Whilst that may be ok for a very specific set of conditions and a specific bird, I would like to be able to set exposure manually and be ready for anything as it were.
This morning, I was stood in sunlight, not a cloud in the sky, and tried manual exposure. I took a test shot of a branch with blue sky behind and adjusted exposure accordingly. A blue tit popped along and after I took the shot and checked the histogram, the white cheek of the bird was blown. In this instance, should I have metered off the grass as you have previously documented? I also want to photograph terns down by the local river. These are obviously going to be the brightest part of the image. Given the same sunlit conditions and nice blue sky, should I meter off the grass beforehand? If there are nice white fluffy clouds, should I meter off the cloud at +3? Would this also be the same method for taking shots of planes at an airshow? I will need to set the shutter speed at 1/200th for prop blur so will need to adjust aperture and ISO appropriately.
Too many questions I know, but my head is buzzing at the mo and I am keen to crack manual exposure :bonk:
I have just started to try manual metering on static bird shots but have up to now cheated byfor example, setting exposure on a tree trunk bathed in sunlight then waited for the bird (treecreeper) to, hopefully, pop along. Whilst that may be ok for a very specific set of conditions and a specific bird, I would like to be able to set exposure manually and be ready for anything as it were.
This morning, I was stood in sunlight, not a cloud in the sky, and tried manual exposure. I took a test shot of a branch with blue sky behind and adjusted exposure accordingly. A blue tit popped along and after I took the shot and checked the histogram, the white cheek of the bird was blown. In this instance, should I have metered off the grass as you have previously documented? I also want to photograph terns down by the local river. These are obviously going to be the brightest part of the image. Given the same sunlit conditions and nice blue sky, should I meter off the grass beforehand? If there are nice white fluffy clouds, should I meter off the cloud at +3? Would this also be the same method for taking shots of planes at an airshow? I will need to set the shutter speed at 1/200th for prop blur so will need to adjust aperture and ISO appropriately.
Too many questions I know, but my head is buzzing at the mo and I am keen to crack manual exposure :bonk:
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Nigel, I would not call it cheating if you are attempting to take charge and precisely set your exposures to suit the subject/scene/lighting. You can use any technique that works for you. I have my favourites, but that doesn't mean there are no other ways to tackle the challenge. My take would be....
If you have clear blue skies and strong sunshine somewhere behind you then one of the easiest manual settings to use is a standard "Sunny 16" exposure. Using such an exposure will usually preserve highlight detali in whites and bright colours.
A "Sunny 16" exposure is one where if you set your aperture to f/16 then your shutter speed should be the reciprocal of your ISO. In other words at 100 ISO your shutter speed would be 1/100. At 200 ISO your shutter speed would be 1/200 and so on.
However, f/16 is seldom a good choice of aperture, so it is usually better to open up wider, maybe to f/8, f/5.6, f/4 or whatever is best for your subject and then to increase the shutter speed to compensate. For example, for BIF you might try f/8, 400 ISO and 1/1600 in bright conditions. For perched birds you could lower the shutter speed and the ISO for better IQ, so long as you can keep the lens steady enough. If you have a fast, sharp prime lens and a good tripod and technique then you could shoot at something like f/5.6, 100 ISO, 1/800 for incredible IQ.
If the sun is not more or less behind you, or maybe there is a little haze, then you may need to increase the exposure slightly. Remember, this approach will be well suited to retaining bright highlight details. If your subject is of darker tones, especially something like a crow or blackbird, then you would be well advised to increase the exposure further, to capture extra detail in the dark tones. That is assuming that you will not blow out the sky, or anything else of importance to your composition, behind the bird.
If your subject is on or over water, or whiteish sand, or snow, or anything else that will reflect brightly and add more light to the subject then you may need to dial the exposure back a touch.
Here's an example where I would personally find the scene overall, and the subject, extremely hard to meter. The whites on the bird are not large enough to be spot metered and I'm certainly not skilled enough to be able to make a judgement about where to place the meter needle if metering off the water. The scene does have a high dynamic range, and will not fit within the range of the histogram. What I did observe is that the subject and scene is sunlit. The sun may not be doing much for the water, but it is certainly making the whites on the bird light up. The easiest option, at least to get things started, was to dial in an exposure equivalent to Sunny 16 and adjust if necessary. Here is the shot as a Sunny 16 capture, with no edits except white balance...
The darker areas do look a little dark, and would need some PP to bring them up, but the whites are awfully close to the right hand edge of the histogram. This exposure might have been improved by going a little brighter, but as a starting point it is very close.
So that's one good yardstick for shooting in bright, sunny conditions.
If the sun angle is not in your favour, or you have conditions other than bright sun, or even if you do have the sun on your side, there are lots of options for metering that will get you very close to the right ballpark. If you have bright, white clouds in your background, and expect them to form part of your scene (after cropping) then spot metering the clouds at +3 is a good starting point, if you shoot raw. However, you need to consider what sort of birds might be your subject, because some white feathers can reflect more brightly than clouds. Backlit clouds can be dazzling, especially relative to your subject. Front lit clouds may not be as bright as the feathers on a gull, swan, magpie and others. If your intended subject is likely to be less reflective (less bright) than the clouds then use the clouds as your +3 target. If the subject may be brighter than the clouds then hold a little in reserve, maybe metering the clouds at +2.3 instead of +3.
Basically, your aim is to capture the highlights in the scene, whether they are in the subject or other areas, as brightly as you can, without overexposing them, so save +3 for the brightest thing you expect the scene to contain.
Another option, which should give you an exposure that will also hold highlight details, is to hold your hand up, with the back of your hand facing the subject direction, and your palm facing back towards you, angled a little so as to "catch" the light from behind you rather than err towards glancing light or shade. You need to ensure your lens hood does not cast a shadow onto your palm!. For my palm, which is pale caucasian skin, setting the meter to +1.3 stops will give me an exposure that will secure my highlights. People with differing skin tones may need to aim for some other value. If I know the subject/scene will have bright content then I stick with +1.3. If I know my subject/scene does not have bright tones, and I do not expect bright tones to enter the scene, then I might aim to meter my palm at +2.3 so that I get a brighter/stronger/less noisy exposure. For palm reading to work you do need to make sure that you and your palm are in the same light as your subject/scene. If you are hiding in the shade of a building or tree while your subject is in the clear then palm reading won't work too well. Equally, if you are in the sunshine and your subject is in shade then the same argument applies.
Metering from grass is another option too. I find that with bright highlights in the scene that lush, green grass metered at -2/3 will give me a good exposure to secure the highlights. Once again, if my subject/scene contains nothing bright (of importance) then I may well increase the exposure by a stop or so. Don't forget, you might end up with something in the scene becoming overexposed, such as the sky, but you may be shooting in the knowledge that you plan to crop it out later, so hanging on to details there is not a concerns. Far better to capture better detail (and lower noise) in your subject than to worry about parts of the scene that are of no concern.
There is nothing stopping you metering off other things too, but you must carefully consider how bright those things are and whereabouts on the tonal scale they should be positioned. Think of it like this....
+3 on the meter is equivalent to (almost) pure white and this is where the brightest parts of the scene can/should be metered if they are indeed brightish/whiteish. The camera will be able to record detail at this level, such as texture in clothing, but it might be difficult to see. You will have the option, in your raw editor, to adjust the rightness if you need to, to reveal the texture concealed in the file. For safety, and if shooting to JPEG, then you can aim a little lower. I like to push to the edge, if I can.
+2 on the meter is just off white and anything there will hold plenty of tonal detail and texture.
+1 1/3 on the meter is where I will set an exposure from my own outstretched palm, if I have bright highlights I need to preserve. If there are no such highlights then I may increase the exposure by around 1 stop.
0 on the meter is just a sort of middle tone, and not very exciting or special. That is where the camera thinks things should be unless you tell it different. This is about the shade that you get from the inside material of a Lowepro camera bag. You'll probably find that concrete pavement is quite close to this tonal value too.
-2/3 on the meter is where I would place lush, green grass, if my scene had bright highlights I needed to preserve. In a scene with no such highlights I would meter grass around 1 stop brighter.
-2 on the meter is very dark but still contains good detail. If you were shooting a dark subject, such as a black horse, dog, cow, bird then you would be looking to expose the animal at around the -2 mark. After all, you don't want a "black" dog to turn out looking "grey", but at the same time you don't want the fur to be turned into a featureless black pool of nothingness. Even then, fur can have shadowy areas, and even a remarkably bright sheen to it, so you need to think about the location you are metering from and whether it should in fact be nearly completely black or actually quite a light black.
-3, for practical purposes is virtually black, and you won't see much in tones captured at -3 on the meter. In truth there is detail recorded there, and at levels below -3, but to see it you will need to brighten the shadow tones and that will start to reveal noise that you may prefer not to see. The higher your ISO, and/or the worse any underexposre, the worse that noise will appear.
So, when you choose to meter from a tree, that is all well and good, but different trees have different tones in their leaves, and in their bark, and those things themselves have shadows and highlights, so while you certainly can meter from them, you need to think about how dark they are relative to the rest of the scene. Metering a part of a tree at 0 might be perfectly correct, but it might be that -1 would be better or maybe +1, or maybe some other figure, depending on the tree itself and how the light is striking it.
Here is a typical example of a shot where I metered the sky at +3. Aesthetically it is overexposed, but my raw capture has recorded as much data as possible, without losing anything inportant to clipping, and it will take but a moment to adjust the aesthetic appearance of the image, without increasing noise or otherwise harming IQ.
Here's another example (poor composition but a good example of what I want to explain, showing the case where the bird's feathers are in some areas brighter than the sky, and in this example are overexposed by around 2/3 stop. That in itself is not a problem, because (a) there is not much in the way of important detail there that needs to be faithfully recorded; (b) the raw headroom will almost certainly allow me to recover some detail in the blown out areas. The important thing to observe is that the sky itself is clearly not a bright white, and it would indeed have been risky to try to meter from this sky at +3. If you evaluate the exposure settings I used for this you will note that they are an exposure 1.7 stops brighter than Sunny 16. Now, given the hazy sky it would be reasonable to expect an exposure a little brighter than that required for full sunshine, and as you see this exposure is pushed around 0.7 stops too bright for these feathers, maybe 1 stop too bright for really dazzling feathers. The other 2/3 stop is for the hazy light. The reason I was set up like this, not to take account of white feathered birds, is because I had been shooting swifts (or sand martins or something like that) and wished to maximise the detail recorded for the darker tones of those birds and their shadowy undersides.
So, even with guidelines to follow it is still important to pay close attention to the results you are achieving in practice and to be willing and ready to fine tune things if needed. On the back of the camera the histogram would almost certainly not make known the small amount of clipping in the feathers, but the blinking highlight warnings in the preview image would have been a useful alert that I was pushing my luck here.
As you may also note, I positioned myself so that the sun was working for me, rather than against me, so that my subject was well lit and the sky was not a luminous light source in the background. If I had been shooting in the opposite direction the birds would have been in their own shadows and the sky would have been much more difficult to control while achieving correct exposure for the birds. Even with the sun behind me, you may note that I have still caught some shadow under the wings, because the sun was so high in the sky. There are many things to consider when going out to shoot and the time of day can matter just as much as everything else. The most difficult thing to do well is to shoot dark, shadowy undersides when the sky is bright behind the bird. Blue skies are often not a problem, but hazy or white skies and backlit cloud can be.
Here's an example where the bird's underside was shaded, but the almost clear blue sky in the background made it easy enough to get a nicely balanced exposure. The exposure here was 1/2000 at f/5.6 and 400 ISO, being 2/3 stop brighter than sunny 16. It has had no exposure related adjustments other then to darken the blacks to create more contrast/punch...
Going back to the example of the blue tit with the blown cheek feathers, so long as nothing else was blown you can probably deduce that you were only out by maybe 1/3 stop or 2/3 stop, so a quick adjustment to your manual exposure to get you where you need to be will then leave you free to carry on shooting without worrying about remetering and adjusting repeatedly from that point. You can adjust your composition, taking in a little more sky, or a little less, for example, and your exposure will remain fixed just as you want it. If the light changes then you might need to re-evaluate your exposure setting.
If you have clear blue skies and strong sunshine somewhere behind you then one of the easiest manual settings to use is a standard "Sunny 16" exposure. Using such an exposure will usually preserve highlight detali in whites and bright colours.
A "Sunny 16" exposure is one where if you set your aperture to f/16 then your shutter speed should be the reciprocal of your ISO. In other words at 100 ISO your shutter speed would be 1/100. At 200 ISO your shutter speed would be 1/200 and so on.
However, f/16 is seldom a good choice of aperture, so it is usually better to open up wider, maybe to f/8, f/5.6, f/4 or whatever is best for your subject and then to increase the shutter speed to compensate. For example, for BIF you might try f/8, 400 ISO and 1/1600 in bright conditions. For perched birds you could lower the shutter speed and the ISO for better IQ, so long as you can keep the lens steady enough. If you have a fast, sharp prime lens and a good tripod and technique then you could shoot at something like f/5.6, 100 ISO, 1/800 for incredible IQ.
If the sun is not more or less behind you, or maybe there is a little haze, then you may need to increase the exposure slightly. Remember, this approach will be well suited to retaining bright highlight details. If your subject is of darker tones, especially something like a crow or blackbird, then you would be well advised to increase the exposure further, to capture extra detail in the dark tones. That is assuming that you will not blow out the sky, or anything else of importance to your composition, behind the bird.
If your subject is on or over water, or whiteish sand, or snow, or anything else that will reflect brightly and add more light to the subject then you may need to dial the exposure back a touch.
Here's an example where I would personally find the scene overall, and the subject, extremely hard to meter. The whites on the bird are not large enough to be spot metered and I'm certainly not skilled enough to be able to make a judgement about where to place the meter needle if metering off the water. The scene does have a high dynamic range, and will not fit within the range of the histogram. What I did observe is that the subject and scene is sunlit. The sun may not be doing much for the water, but it is certainly making the whites on the bird light up. The easiest option, at least to get things started, was to dial in an exposure equivalent to Sunny 16 and adjust if necessary. Here is the shot as a Sunny 16 capture, with no edits except white balance...
The darker areas do look a little dark, and would need some PP to bring them up, but the whites are awfully close to the right hand edge of the histogram. This exposure might have been improved by going a little brighter, but as a starting point it is very close.
So that's one good yardstick for shooting in bright, sunny conditions.
If the sun angle is not in your favour, or you have conditions other than bright sun, or even if you do have the sun on your side, there are lots of options for metering that will get you very close to the right ballpark. If you have bright, white clouds in your background, and expect them to form part of your scene (after cropping) then spot metering the clouds at +3 is a good starting point, if you shoot raw. However, you need to consider what sort of birds might be your subject, because some white feathers can reflect more brightly than clouds. Backlit clouds can be dazzling, especially relative to your subject. Front lit clouds may not be as bright as the feathers on a gull, swan, magpie and others. If your intended subject is likely to be less reflective (less bright) than the clouds then use the clouds as your +3 target. If the subject may be brighter than the clouds then hold a little in reserve, maybe metering the clouds at +2.3 instead of +3.
Basically, your aim is to capture the highlights in the scene, whether they are in the subject or other areas, as brightly as you can, without overexposing them, so save +3 for the brightest thing you expect the scene to contain.
Another option, which should give you an exposure that will also hold highlight details, is to hold your hand up, with the back of your hand facing the subject direction, and your palm facing back towards you, angled a little so as to "catch" the light from behind you rather than err towards glancing light or shade. You need to ensure your lens hood does not cast a shadow onto your palm!. For my palm, which is pale caucasian skin, setting the meter to +1.3 stops will give me an exposure that will secure my highlights. People with differing skin tones may need to aim for some other value. If I know the subject/scene will have bright content then I stick with +1.3. If I know my subject/scene does not have bright tones, and I do not expect bright tones to enter the scene, then I might aim to meter my palm at +2.3 so that I get a brighter/stronger/less noisy exposure. For palm reading to work you do need to make sure that you and your palm are in the same light as your subject/scene. If you are hiding in the shade of a building or tree while your subject is in the clear then palm reading won't work too well. Equally, if you are in the sunshine and your subject is in shade then the same argument applies.
Metering from grass is another option too. I find that with bright highlights in the scene that lush, green grass metered at -2/3 will give me a good exposure to secure the highlights. Once again, if my subject/scene contains nothing bright (of importance) then I may well increase the exposure by a stop or so. Don't forget, you might end up with something in the scene becoming overexposed, such as the sky, but you may be shooting in the knowledge that you plan to crop it out later, so hanging on to details there is not a concerns. Far better to capture better detail (and lower noise) in your subject than to worry about parts of the scene that are of no concern.
There is nothing stopping you metering off other things too, but you must carefully consider how bright those things are and whereabouts on the tonal scale they should be positioned. Think of it like this....
+3 on the meter is equivalent to (almost) pure white and this is where the brightest parts of the scene can/should be metered if they are indeed brightish/whiteish. The camera will be able to record detail at this level, such as texture in clothing, but it might be difficult to see. You will have the option, in your raw editor, to adjust the rightness if you need to, to reveal the texture concealed in the file. For safety, and if shooting to JPEG, then you can aim a little lower. I like to push to the edge, if I can.
+2 on the meter is just off white and anything there will hold plenty of tonal detail and texture.
+1 1/3 on the meter is where I will set an exposure from my own outstretched palm, if I have bright highlights I need to preserve. If there are no such highlights then I may increase the exposure by around 1 stop.
0 on the meter is just a sort of middle tone, and not very exciting or special. That is where the camera thinks things should be unless you tell it different. This is about the shade that you get from the inside material of a Lowepro camera bag. You'll probably find that concrete pavement is quite close to this tonal value too.
-2/3 on the meter is where I would place lush, green grass, if my scene had bright highlights I needed to preserve. In a scene with no such highlights I would meter grass around 1 stop brighter.
-2 on the meter is very dark but still contains good detail. If you were shooting a dark subject, such as a black horse, dog, cow, bird then you would be looking to expose the animal at around the -2 mark. After all, you don't want a "black" dog to turn out looking "grey", but at the same time you don't want the fur to be turned into a featureless black pool of nothingness. Even then, fur can have shadowy areas, and even a remarkably bright sheen to it, so you need to think about the location you are metering from and whether it should in fact be nearly completely black or actually quite a light black.
-3, for practical purposes is virtually black, and you won't see much in tones captured at -3 on the meter. In truth there is detail recorded there, and at levels below -3, but to see it you will need to brighten the shadow tones and that will start to reveal noise that you may prefer not to see. The higher your ISO, and/or the worse any underexposre, the worse that noise will appear.
So, when you choose to meter from a tree, that is all well and good, but different trees have different tones in their leaves, and in their bark, and those things themselves have shadows and highlights, so while you certainly can meter from them, you need to think about how dark they are relative to the rest of the scene. Metering a part of a tree at 0 might be perfectly correct, but it might be that -1 would be better or maybe +1, or maybe some other figure, depending on the tree itself and how the light is striking it.
Here is a typical example of a shot where I metered the sky at +3. Aesthetically it is overexposed, but my raw capture has recorded as much data as possible, without losing anything inportant to clipping, and it will take but a moment to adjust the aesthetic appearance of the image, without increasing noise or otherwise harming IQ.
Here's another example (poor composition but a good example of what I want to explain, showing the case where the bird's feathers are in some areas brighter than the sky, and in this example are overexposed by around 2/3 stop. That in itself is not a problem, because (a) there is not much in the way of important detail there that needs to be faithfully recorded; (b) the raw headroom will almost certainly allow me to recover some detail in the blown out areas. The important thing to observe is that the sky itself is clearly not a bright white, and it would indeed have been risky to try to meter from this sky at +3. If you evaluate the exposure settings I used for this you will note that they are an exposure 1.7 stops brighter than Sunny 16. Now, given the hazy sky it would be reasonable to expect an exposure a little brighter than that required for full sunshine, and as you see this exposure is pushed around 0.7 stops too bright for these feathers, maybe 1 stop too bright for really dazzling feathers. The other 2/3 stop is for the hazy light. The reason I was set up like this, not to take account of white feathered birds, is because I had been shooting swifts (or sand martins or something like that) and wished to maximise the detail recorded for the darker tones of those birds and their shadowy undersides.
So, even with guidelines to follow it is still important to pay close attention to the results you are achieving in practice and to be willing and ready to fine tune things if needed. On the back of the camera the histogram would almost certainly not make known the small amount of clipping in the feathers, but the blinking highlight warnings in the preview image would have been a useful alert that I was pushing my luck here.
As you may also note, I positioned myself so that the sun was working for me, rather than against me, so that my subject was well lit and the sky was not a luminous light source in the background. If I had been shooting in the opposite direction the birds would have been in their own shadows and the sky would have been much more difficult to control while achieving correct exposure for the birds. Even with the sun behind me, you may note that I have still caught some shadow under the wings, because the sun was so high in the sky. There are many things to consider when going out to shoot and the time of day can matter just as much as everything else. The most difficult thing to do well is to shoot dark, shadowy undersides when the sky is bright behind the bird. Blue skies are often not a problem, but hazy or white skies and backlit cloud can be.
Here's an example where the bird's underside was shaded, but the almost clear blue sky in the background made it easy enough to get a nicely balanced exposure. The exposure here was 1/2000 at f/5.6 and 400 ISO, being 2/3 stop brighter than sunny 16. It has had no exposure related adjustments other then to darken the blacks to create more contrast/punch...
Going back to the example of the blue tit with the blown cheek feathers, so long as nothing else was blown you can probably deduce that you were only out by maybe 1/3 stop or 2/3 stop, so a quick adjustment to your manual exposure to get you where you need to be will then leave you free to carry on shooting without worrying about remetering and adjusting repeatedly from that point. You can adjust your composition, taking in a little more sky, or a little less, for example, and your exposure will remain fixed just as you want it. If the light changes then you might need to re-evaluate your exposure setting.
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Tim, thanks once again for a brilliant explanation of how to expose manually under different conditions.
Lots to take in but I will certainly be giving it a go with static birds, birds in flight and at an upcoming airshow. Should be fun
I'll need to get myself a quick ready reckoner of the sunny 16 rule and calculate the variable combinations to still maintain the equivalent of sunny 16
Lots to take in but I will certainly be giving it a go with static birds, birds in flight and at an upcoming airshow. Should be fun
I'll need to get myself a quick ready reckoner of the sunny 16 rule and calculate the variable combinations to still maintain the equivalent of sunny 16
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I'll need to get myself a quick ready reckoner of the sunny 16 rule and calculate the variable combinations to still maintain the equivalent of sunny 16
As will I, I'd better spend half a day working it out too as I am really bad with numbers.
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Battlestar Galactica.
Is this thread a contender for thread of the year? I think so.
Tim, awesome stuff.
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pity I'm in a grey office all day at work
If it's 18% grey you shouldn't have a problem with exposure
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Here is a three page article which I think describes in a more digestable way, and with more useful examples, the points I have been making about maximising exposure by metering important highlights at +3 stops. If you didn't follow what I have been saying then this might help it sink in....
http://daystarvisions.com/Docs/Tuts/DCExp/pg1.html
http://daystarvisions.com/Docs/Tuts/DCExp/pg1.html