shutter speeds with filters

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appletart

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Tim
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i am really struggling with learning shutters speeds when i have a filter on my lens... anyone help... seen charts but go straight over my head

for example, i have an nd10 filter... i tend to shoot f8... how long do i need to have shutter open for, to get the correct exposure?

i also have an infrared filter (720nm IR), and am aware that i need long exposures to get a decent picture..

anyone able to give a few pointers?

thanks in advance...
 
As a general rule, if your camera is a SLR, it will give you a correct(ish) reading automatically, whether you have a filter on the lens or not.

However I have never used a 10 stop ND, and it could be that the readings you would get using one are outside the abilities of your camera to meter accurately.

If you're not sure about using meter readings generally, use the camera on normal subject matter, in normal light conditions. Don't try to run before you can walk!
 
appletart said:
for example, i have an nd10 filter... i tend to shoot f8... how long do i need to have shutter open for, to get the correct exposure?
Click to expand...

Through the lens metering systems will cope with most filters, but with very strong filters, I would take a meter reading without the filter, and then add the corresponding number of stops once the filter is attached.

For example with a 10-stop ND filter - if you're reading say, 1/250 sec at f/8, and you wanted to keep that same aperture, then your shutter speed would become 4 seconds. You could open your aperture a little to say f/4, then your shutter speed would be 1 second.
 
yeah, i have a slr... a 450d...

i admit to being a complete novice when it comes to filters, a metering systems. just saw infrared shots and thought would give it a try...

so i am going to show my complete stupidity here... i have my camera, and the filter attached... what do i do exactly? :(
 
The TTL (Through The Lens) meter of your SLR will measure the correct exposure fairly accurately and, unless it is set on manual, take the picture.

It will give a good result for an averagely-lit subject. If it is a very dark or light subject you will need to add exposure compensation one way or the other.

Dark subject = less exposure
Light subject = more exposure.

This is because the meter is calibrated to give an accurate result on an average subject.

If you have filter on your lens which cuts down the amount of light reaching it the meter will automatically measure it correctly.
 
I can't help you with regards to infra red photography as I've never tried it.

But the thing to bare in mind is that any filter you put in front of a lens, apart from UV clear filters, will result in a loss of light. Each filter has what's known as a filter factor, which indicates the strength and how much light that filter will absorb. There should be a leaflet supplied with the filter telling you what this factor is.

I would start of by setting the camera to manual and take a meter reading without any filter on your lens. Let's say it reads 1/500 sec @ f/8, and you wanted to keep this aperture setting. If you attach a 2-stop filter, the speed would drop to 1/125 sec at the same aperture. With a 3-stop filter, the speed would be 1/60 sec at f/8; with 4-stops, you'd be down to 1/30 sec, etc.

As Jerry has also mentioned, your SLR should cope OK with the weaker filters even when set to auto, and you will be able to take readings with the filter attached. But with something like a 10-stop ND filter, as it's very strong, I'd personally take a meter reading with no filter on and then manually add on the required 10-stops once I've attached the filter on.
 
appletart said:
ok, that makes sense. but how do i add on the 10-stops?
Click to expand...

Does your camera have manual control whereby you can set both aperture and shutter speeds yourself? Let's go back to my first example, if your meter reading says 1/250 sec @ f/8 without any filter and you wish to use f/8, then switch over to manual and select the shutter speed yourself. I don't know your camera so I'm guessing it'll go down to 1 second, so you'd have to set 'B' and then time the exposure. From 1/250 sec, 10-stops will mean you'd have to expose for 4 seconds to get the correct exposure.
 
1 stop change = shutter speed x2 or x1/2
2 stop change = shutter speed x4 or x1/4
3 .. .. = .. .. x8 or x1/8
etc

or you can go up or down the aperture range to get the same result.

1.4, 2, 2.8,4,5.6,8,11,16,22 (I think these are whole stops...)


One stop measured either by change of shutter speed or aperture (or ISO) either halves or doubles the amount of light reaching the sensor.

I'd suggest getting the hang of this sort of thing without adding complications like 10 stop filters....
 
yeah, it does have a full manual settin so i can do that.... again, soundin really stupid. how do a do a metre reading? press button 1/2 down?
 
appletart said:
yeah, it does have a full manual settin so i can do that.... again, soundin really stupid. how do a do a metre reading? press button 1/2 down?
Click to expand...

Well with cameras I've worked with, yes, slight pressure on the shutter release will activate the meter. You can take a reading with the camera on auto if you want, but if there is an aperture you wish to use, then I'd set the camera to manual and select f/8, or whatever aperture you wish to use, and see what the meter reads as the correct speed. Do this without the filter. Once you have the reading, just manually select your speed for an extra 10-stops with your filter on.

If you wanted to, try using your ND filter with the camera on auto. It may cope OK or maybe not. All my cameras are manual, so I'm not sure how your meter would cope with such a strong filter. Certainly weaker filters won't present any problems.
 
I've only done a little infrared with the 450d, but in my experience your camera will only meter correctly in live view mode. I couldn't tell you why, but that's what I found. You will need to cover your viewfinder to stop stray light getting in. The cover should be attatched to your neck strap. For exposures loner than 30 seconds you will need a remote release. It's almost certain that you will need exposures longer than 30 for infrared.
 
jerry12953 said:
As a general rule, if your camera is a SLR, it will give you a correct(ish) reading automatically, whether you have a filter on the lens or not.
Click to expand...

Interesting you should say that. At the weekend, although it was dull, I decided to test whether the 7d could be used with a R72 infra-red filter. The camera metered almost exactly the same with and without the filter. i.e. f/5.6 without, f/5.6 with, both 1/100!!!
Needless to say, that the IR photo was a tad dark, being equivalent to an ND10!
 
coldpenguin said:
Interesting you should say that. At the weekend, although it was dull, I decided to test whether the 7d could be used with a R72 infra-red filter. The camera metered almost exactly the same with and without the filter. i.e. f/5.6 without, f/5.6 with, both 1/100!!!
Needless to say, that the IR photo was a tad dark, being equivalent to an ND10!
Click to expand...

Live view, or non live view? I have no idea why it should make a difference but I've found that it does
 
Non live view. It is strange, 3 years ago, I used primarily live view. Then the 400d didn't have it, and now I am used to using the viewfinder again. It is easier to hold a long lens not using live-view I think.
On the 400d, it does correctly adjust. With the 7d, it didn't Not a problem really, as with IR it is kinda a guess-take-retake situation anyway (at least, I find so).
 
coldpenguin said:
Interesting you should say that. At the weekend, although it was dull, I decided to test whether the 7d could be used with a R72 infra-red filter. The camera metered almost exactly the same with and without the filter. i.e. f/5.6 without, f/5.6 with, both 1/100!!!
Needless to say, that the IR photo was a tad dark, being equivalent to an ND10!
Click to expand...

Ok, sorry, I've no experience of infra-red.

I'd put it in the same category as an ND10. Get experience without first!
 
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