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  1. #1

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    Using a Dslr as a preview for film long exposures

    Hello all- Thanks you very much for taking the time to read my post/question. Ive been getting into long exposure night time photography lately, using a variety of films (so far Acros and Ektar). Im struggling a little with getting a proper exposure, or at least computing for one. So, my question is ... is there anything inherently incorrect in using my DSLR as a 'polaroid' for the scene Im shooting (assuming Ill account for proper reciprocity of the film when I move to the film camera)? I ask because I was doing some long exposure black and white work last night, using a meter and computing by hand (on acros) and now that Ive developed the film, most of my shots came out significantly over exposed.... so I would like a little 'insurance' that my math is correct before I expose the film and I wasn't sure if there are other factors to account for.

    Thoughts?


    Thanks all!

  2. #2
    Eric Rose's Avatar
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    Having done a fair amount of night photography with film and digital I would say you would be better off just learning how your film behaves and leave out the digital stuff. The way each responds to long exposures is just to different. One thing you might want to experiment with depending on the subject matter is ND grad filters to even out the exposures if you have one area that is brighter than others. Night photography at least to me is an organic thing. You just learn to "feel" what the right exposure is once you have enough experience. I have used my darkroom dodging tools in front of the lens during exposures as well. Night photography is one of my favorite things.
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  3. #3
    David A. Goldfarb's Avatar
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    Better off just experimenting by bracketing exposures on a night reserved for testing, when you're not photographing anything important, and keeping a record and making a table for reciprocity correction that you can use in the future. As you use it, you may find you can do some refinement, adjusting development time to correct contrast with long exposures as well. Once you have that, you'll be all set, you can concentrate on the aesthetic issues rather than the technical ones, and you don't need to test with another medium that will still require a conversion table anyway.
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  4. #4
    Hatchetman's Avatar
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    Please give details of meter, camera, scene, exposure, etc. Let's address why the shots were overexposed prior to resorting to a crutch.

  5. #5

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    In regards to Mr Hatchetman.... I was shooting acros at sunset, over looking the ocean. I was using about 8 stops of ND and using an app on my phone to compute the add exposure time needed to comp for the ND filters, which figured most exposures around 15-30 seconds and some at a minute. Looking back, I realize that that was way too much time.. which is why I was wondering If I could use a dslr to at least get me 'in the ball park' to bracket from that point on.

    Its clear most are going to be against using DSLRs as a starting point, so what if I use a polaroid back with the same rated film as a starting point? Im shooting mostly with a Mamiya TLR but I also have a 645af w/ a Polaroid back that I could use to test where the exposure should aprox be.

    Thoughts?

  6. #6
    Hatchetman's Avatar
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    well my first thought is your ND filter may not actually be 8 stops, which would be pretty unusual as far as I know. A filter labeled "ND8" means 1/8 the light or 3 stops.

  7. #7

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    Quote Originally Posted by bibowj View Post
    In regards to Mr Hatchetman.... I was shooting acros at sunset, over looking the ocean. I was using about 8 stops of ND and using an app on my phone to compute the add exposure time needed to comp for the ND filters, which figured most exposures around 15-30 seconds and some at a minute. Looking back, I realize that that was way too much time.. which is why I was wondering If I could use a dslr to at least get me 'in the ball park' to bracket from that point on.

    Its clear most are going to be against using DSLRs as a starting point, so what if I use a polaroid back with the same rated film as a starting point? Im shooting mostly with a Mamiya TLR but I also have a 645af w/ a Polaroid back that I could use to test where the exposure should aprox be.

    Thoughts?
    A potential problem would be different reciprocity characteristics between the films. You're proposing to use neg film anyway - which has good tolerance of excess exposure. The second camera is just adding complexity to your shoot.

  8. #8

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    ohh, and now that Ive scanned the images..they were actually quite underexposed. Its just that I didn't account for the exposure correctly. I was metering reflective , at a far off area.. no biggie ..just a match mistake on my part. I did one have that turned ok ish.. but the rest were just my screw up.

  9. #9

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    The ok one

    This one worked out.
    Attached Thumbnails Attached Thumbnails small322_6546.jpg  

  10. #10
    wiltw's Avatar
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    Quote Originally Posted by bibowj View Post
    Im struggling a little with getting a proper exposure, or at least computing for one. So, my question is ... is there anything inherently incorrect in using my DSLR as a 'polaroid' for the scene Im shooting (assuming Ill account for proper reciprocity of the film when I move to the film camera)?!
    Film is subject to 'reciprocity failure'...that is, at very long exposure times due to very low levels of light, twice the time does NOT provide twice the response to light...you might see only 20% increase in film response (density) for 100% increase in time, for example...the 'curve' in the response curve of film. In comparison, digital is largely LINEAR in response.

    Your 'underexposure' in post 8 proves the result of reciprocity failure.
    Last edited by wiltw; 07-12-2014 at 02:32 PM. Click to view previous post history.

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