1. Dorsetsnapshot

    Dorsetsnapshot

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    Hi All,

    I'm a bit embarrassed about this, but there you go.

    Anyway, I've recently bought some filters, ND and a long stopper... I'm aware that you compose your shot, take your 'base exposure' to see what your exposure currently is, then you calculate how long your shot will be with each filter..

    My question is, how do you work out your base exposure? Is that just taking a shot in auto and reading the data on the camera? That seems a tad simple to me, but I thought I'd ask as i'll get no where otherwise!

    Thanks,
     
  2. scott199

    scott199

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    not stupid at all, ive always wondered the same but not had the guts to ask :D
     
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  3. Dorsetsnapshot

    Dorsetsnapshot

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    Lets hope someone with experience helps us out here! :banana:
     
  4. Giles2373

    Giles2373

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    The way I do it is to set my ISO (ideally as low as possible so lets assume 100), then set my f-stop - lets assume f11 and then expose as per the camera suggestion at that point for shutter speed. Your metering mode will have an affect. on this. As you're presumably using a tripod the length of time isn't too important (depending on what effect you are trying to achieve, although with a long stop I'm assuming motion blur).

    Lets say the camera then comes back with 1 second, you can then calculate what you need to convert that to with the long stopper filter. Does that make sense?
     
  5. Dorsetsnapshot

    Dorsetsnapshot

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    Ish, but more due to my lack of understanding, not the way you explained it. Am I right in thinking you go into Manual mode, input the ISO and F Stop, and then take a photo, then take whatever shutter speed that camera has used? And then calculate your exposure for the filters?
     
  6. riddell

    riddell

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    It all depends on what you are looking to achieve and why you are using an ND filter.

    You'll need to work in manual, but then it depends on whether your use of the ND filter is because you need to adjust the shutter speed or the aperture or both.
    Personally you'll rarely want to adjust the ISO, but there have been occasions in the past where, the use of an ND filter has pushed things a bit too much, and then I've dropped to ISO 50 to pull it back a bit.
     
  7. PaulButler

    PaulButler

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    There are a number of ways to do this by using the camera's meter.

    A quick and dirty is to have the camera in matrix metering (for Nikon) or evaluative (I think that is the Canon version). Set to Aperture priority. Set at base ISO. Set the aperture to what you want and half press the shutter (or press whatever to activate the meter) pointing at your target and read off the shutter speed for the given aperture.

    Then do the maths on the shutter speed for the ND filter (e.g. 10 stops or use an app ;) ) - Then put the camera into manual, set the shutter speed or bulb/remote mode as appropriate (more than 30 secs and you need to use bulb/remote and ideally some form of remote release). Compose the shot properly (if not already done) and fit the filters. Take the shot and then decide if you want longer or shorter duration.

    On my Nikon setting the shutter to press to open and press again to close (I call it remote mode - I'm sure there is a proper term but ....) is a case of rotating the rear command dial when in manual until the two dashes appear. Then when the shutter release is pressed it opens and won't close until you press the shutter release again, hence why using a remote is a good idea.

    The reason for tweaking the duration is that not all stoppers are an exact number of stops, and tbh a few secs here or there rarely makes a big difference when you are into 10's of seconds of exposure. Also make sure the eyepiece is covered to when shooting.
     
  8. PaulButler

    PaulButler

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    Not sure I understand what you are saying here ... by using an ND you will be increasing the exposure time (slower shutter speed) and then dropping the ISO will increase it further (if base is 100 then dropping to 50 will double exposure time) - is that what you meant as I didn't read it like that ...
     
  9. scott199

    scott199

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    so in beginner terms (me) is this correct.

    Choose your iso and aperture, let's say iso 100, and i want F11, now focus/meter from the camera on my scene, cam says for perfect exposure i need 1/500 shutter, so I then add an nd4, to correct the exposure i reduce the shutter by 2 stops (nd4) to 1/125

    i know all these numbers are wrong, but for ease of explanation am i basically correct ??
     
  10. john.margetts

    john.margetts

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    What is wrong with simple? Nearly everything is simple once you know what you are doing - and with this you do know.
     
    Last edited: Aug 29, 2018
  11. riddell

    riddell

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    Yes, PaulButler.

    By using an ND filter, you have 3 choices, and it really does depend on what you want to do.
    I suppose what I said is confusing in one way, but I'm usually working in manual, and what you say is correct.
    I've had a few shoots lately, where as well as achieving the shutter speed I need, I've also needed to achieve a certain aperture for a certain depth of field. I've only been able to do that by switching to ISO 50
     
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  12. AgentOrange76

    AgentOrange76

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    So Im a relative beginner but seem to have a good system in place.

    I use aperture priority and let the camera calculate shutter speed. I have a 6 and 10 stop ND screw on filters at the moment
    ISO 100 generally with aperture f8 or f11.

    The simply way - Compose the shot, add the ND filter (I use live view to compose through the filter)Then focus and meter the shot by half pressing the shutter. I check the shutter speed and if I feel that its slow enough for what I want I take the photo. If the photo is not how I want e.g water not smooth enough or too smooth, Image too light or dark I will adjust the aperture or ISO.

    Not so simple (Full manual method) - I have tried composing, taking a shot, noted the shutter speed, attached the filter, adjusted the shutter speed by the number of stops (either by adding up stops or using an app on my phone) and then taking the photo. Generally I get a similar shutter speed as metering through the filter and you would need to have got the exposure correct in the initial test image.
    To do that you would need to be in Manual mode, set the ISO (as you are on tripod for ND then this will likely be 100) set the aperture (assume landscape shot) so say F8. On you camera you should then have a meter line that will indicate the current shutter speed is to slow or fast, adjust the shutter speed untill this line is in the middle and take a shot. If it looks good thats your base ISO, Aperture and shutter speed. Add the ND filter, adjust the shutter speed by 10 stops (assume 10 stop ND) and take your shot. Adjust 1 or 2 of the 3 settings to achieve the image you want.

    Example. I was in london yesterday and sat on the side of the Thames in a pub
    Camera set up, took a shot with the camera ISO 100, F8 1/500

    I wanted to smooth the water and as it was bright used the 10 stop, This gave me ISO 100, F8 2seconds (exactly what the calculator gives)
    This didnt smooth the water enough so changed the Aperture to F11 which gave me a 4second shutter speed. Perfect water for my liking

    If you are in manual mode you would needed to have changed both the Aperture down 1 stop to F11 and the shutter up 1 stop to 4 seconds

    When I got my filters I found a couple of locations that would be typical of what i would want to shoot and just sat there playing with the settings to see what affect they had, I now have a feel for how long I need on the shutter to create smooth water depending on how much ripple there is, or how blurred I want a water fall to look. Too long is generally worse than too short for my taste.

    Hope that helps and wasnt teaching you to suck eggs
     
    Last edited: Aug 29, 2018
  13. gad-westy

    gad-westy

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    Sorry if it's been mentioned already but depending on the strength of the ND filter you may just be able to shoot as normal in whatever exposure mode you normally use, may be no need to go into manual mode or carry out calculations. If there is enough light for the camera to meter (and focus if you've not already locked that down), you can potentially just shoot as normal.

    If you're into 10 stoppers and the like, probably not so much! But I'm sure that's all been covered already above.
     
  14. Teflon-Mike

    Teflon-Mike

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    A Neutral Density filter block light getting into the lens.
    IF you are using an 'auto' exposure mode on the camera, that measures the light TTL or Through-Taking-Lens... it should compensate for the 'filter factor' because the meter only sees the light that gets through the lens, AND the filter, and bases settings on that meter reading.

    So, if metering full Auto, Aperture-Priority or similar you shouldn't need to do anything. If shooting in Manual mode.... where do you get your meter reading from to make your own shutter/aperture/ISO settings from? Most likely the Hi/Lo indicator in the vier-finder, from TTL meter.... same deal applies.... that sees light after the filter, it should compensate for the filter.

    The 'Niggle' is if you are using a heavy ND or big-stoppa filter..... apart from the cliche of over-milked waterfalls and waves, which is a BIG niggle in my book, but still.... the niggle, is that with the filter in place.... you probably cant see bog all through the lens in the view-finder....... this begs removing the filter to compose shot, then replacing to expose.....
    - If in an auto or semi auto mode, camera should re-meter after you replace filter, and recalculate exposure settings; you aught not have to make any correction or compensation.
    - In manual.... as before; if you use the Hi/Lo TTL meter in the view-finder, to make settings, after composition, and after adding filter; that should be good.
    The issue is if you meter before adding filter, and then make settings, when you will have to add in the filter factor, and if its say a 3-Stop filter, add three stops of shutter steed, or three stops of aperture or three stops of ISO, or permutations of.

    A-N-D filter-factors provided by filter makers aren't always all that reliable, and you may have to adjust exposure a stop or tow either way depending on results.

    There's also the small niggle in semi auto modes, particularly shutter priority, that there isn't enough f-stops on the aperture for the metering system to open up enough stops for the shutter speed you set... milking waves or waterfalls, this is unlikely an issue as you will probably use aperture priority, but worth noting; it can hit the buffers and not give settings to balance exposure metering.

    BUT using 'Coupled' Through-Taking-Lens metering, as built in to most modern cameras... slapping filter in-front of lens, metering should work as intended with no other intervention from you... a LONG as you let the camera meter through the filter.

    If you are using a hand-held meter, and taking an incident or reflected light reading, then the filter factor is more important, and again, you have to add the filter factor into your computations to derive aperture/shutter/ISO settings... and the filter factor quoted by the maker may not be all that accurate, and on heavier big-stoppa filters, and more cheaper ones, be even more inaccurate; on a cheap heavy big-stopps with quoted filter factor of say 10-stops, you might get under-exposed images, and have to up exposure by as many as 3-stops to get an acceptable exposure...... so some trial and error may still be required.

    It all depends on how you are metering....

    A-N-D.. having mentioned milking water-falls..... worth mentioning that if your objective is actually very very long exposure effects..... metering is likely to go a bit to pot any-way.....

    Metering measures the intensity if light at the instant of measurement. If you have a water-fall, you have a scene with highlights catching the drops of water, that are moving down the frame. In the instant of metering, or short exposure, they don't move very far.. give it a long exposure, they do... now you have the same high-lights being recorded over much larger portion of the frame, during that long exposure time..... depending on how many high-lights and how far they move, and how long your long exposure is, the accuracy of a instantaneous exposure value can vary from not far off to hugely off.... THIS is one of the reasons that milking waterfalls was set as an academic exercise, NOT in effect, or artistic interpretation, but where the mechanics of the machine fall down, and experience and judgement come into play to dial in compensation, and to judge the most pleasant exposure A-N-D effect, and NOT be reliant on the maths and the meters.... and that is the lesson now so often NOT learned by the exercise, trying to do it all by the books and the numbers in the digital world. Which may be worth taking note of.
     

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