Using a digital camera to test exposuregreenspun.com : LUSENET : Large format photography : One Thread
I'm sure this question has been posted before, but I can't seem to find it. If there is a thread, please point me to it if it covers the question below.
I'm interested in using a digital camera to test exposure instead of a polaroid back on my 4X5.
How does this work if you're stopped down to f/45, and your digital camera only stops down to f/22? Do you simply calculate the stop difference in you head and then adjust the shutter speed accordingly? Aside from filter factors and close-up shots, what are the disadvantages to using digital instead of Polaroid, what will I be missing? What are some advantages, other than cost, weight, and set-up time?
I remember seeing an article in Outdoor Photographer, but I'll be darned if I can remember the issue number.
Any suggestions on which digital camera to get (based solely on the ability to adjust for proper exposure, rather than if it has 1000 Megapixels, or not....then again if it had 1000 megapixels, I wouldn't be doing LF :-p)
-- Peter Chipman (email@example.com), March 20, 2002
Here's an article on using a digital camera as light meter:
-- Åke Vinberg (firstname.lastname@example.org), March 20, 2002.
The link above is a good reference...to offer you a few other bits.. you wrote... How does this work if you're stopped down to f/45, and your digital camera only stops down to f/22? Do you simply calculate the stop difference in you head and then adjust the shutter speed accordingly?
Yes, this is correct.
Aside from filter factors and close-up shots, what are the disadvantages to using digital instead of Polaroid, what will I be missing?
Regardless of which you use, the key is, be sure the test film / digital camera has the same amount of exposure lattitude as the film you are using. Polaroid B&W, in my opinion has exposure latitude close to chrome film, but much less than neg film. So you have to keep this in mind. Some of the CMOS digital sensors have a few stops more than chrome film, about equal to neg film. But you have to test this for each Polaroid film or digital camera you plan to use vs. the film you plan to shoot with.
I bet it won't be too long.... instead of a spot meter, we will have an LCD dispaly meter, in which we can see the scene, dial in the number of stops our film has in exposure latitude, so many +, and so many - from the exposure setting ..... then move the exposure dial till the display gives us the best exposed image, read the settings, adjust for bellows or filters and were done! No more polaroids, no more guessing, and no need to worry about changing light! Just mount it on your tripod leg and keep looking glancing at it to be sure nothing has changed! Would be amazing for flash work! Sekonic or Gossen...if your listenting.... please.....
-- Bill Glickman (email@example.com), March 20, 2002.
Good info, but it doesn't fully answer my quesiton(s) (BTW, I like the histogram that comes up in the LCD panel).
-- Peter Chipman (firstname.lastname@example.org), March 20, 2002.
I also use split ND filters a fair amount, so I'm guessing that Polaroid would be a better choice in this instance, as I'd have proof, right away, that I balanced the exposure on the clear and graduated portion of the shot. However, the cost and weight of Polaroid is still an issue for me. Has anyone gone on a long-term outdoor assignment (a week or more) on foot with just the digital camera for exposure feedback (and light meter of course)? How was your experience compared to your previous use of Polaroid?
Also, how many people simply bracket a little extra and forgo both Polaroid and digital in favor of less hastle?
-- peter chipman (email@example.com), March 20, 2002.
Interesting article. While we're on the subject, does anyone use a digital camera in place of a color temperature meter (i.e., set on daylight or tungsten to match the film then filter with the same filters you would use on the camera until it looks right)?
-- David Goldfarb (firstname.lastname@example.org), March 20, 2002.
A camera with a histogram function is really the only way to judge the exposure properly in the field. The playback on an LCD screen can be very misleading, since the highlights nearly always appear blown out on the LCD screen, even when they're not clipped at all.
ISO figures given to digital cameras appear to be only a nominal speed rating.
I'm now on my second digital camera. (I have the Fuji4900z and lately a Minolta Dimage 7, and I've also had the use of Olympus and Nikon digitals.) Even two digicams don't always agree with each other on exposure, let alone with a handheld meter or a TTL film camera.
I'd do some extensive testing and calibration before I relied on a digicam exposure being even close to that of film.
The Dimage 7s histogram function is extremely useful, but the camera seems a lot more sensitive than its 100 ISO minimum rating would suggest. The Fuji, OTOH, seems to stick quite closely to its rated 125 ISO.
There's also a noticeable trade-off between white-balance and speed. The further you set the white-balance away from daylight, the more the camera's real sensitivity varies from its stated ISO rating.
Your point about the minimum aperture of a digital camera is a good one Pete. The situation is worse than you imagine though. All consumer digicams with a fixed lens have minimum apertures that stop at around f/8 or f/11. This is partly because the lens quality would be degraded too much by diffraction at smaller apertures, and partly for mechanical reasons. A 12mm lens would need a tiny 0.75mm diaphram opening at f/16! Not an easy thing to engineer reliably when it has to be stopped down by a servo mechanism.
So, you'll have to count the stops and shutter speeds off in your head to get from f/8 down to f/45 or whatever, or use an existing light meter scale to do it for you. In low light, you might also encounter reciprocity effects on film that the digicams don't suffer from.
Good idea about using the digital as a CT meter David, but again, the LCD display is almost useless for this purpose. You'd have to have access to a computer and calibrated monitor, IMHO.
Personally, I use my digital cameras for taking pictures in their own right, and they've supplanted my 35mm shooting A LOT. As far as LF photography goes, I'd use a digital for scouting locations and viewpoints, rather than carry one in addition to all the LF gear. But then I've never felt the need to shoot Polaroids either.
-- Pete Andrews (email@example.com), March 21, 2002.
You're not likely to get much more from a digital camera as a meter than you would a spot or ambient meter. The reasons are the latitude differences, and the way the LCD shows the scene.
Depending on your film, you will likely have a fair difference in what the camera can record or show on the LCD, and what your film actually records. You could experiment with different combinations of digital cameras and film until you found something suitable, but it seems like a lot more work than simply knowing your film and meter.
As to the in camera histogram, it is very valuable to show what's blown out for the digital camera, but that may not translate directly to the film you're using. Hope this helps.
-- Michael Mahoney (firstname.lastname@example.org), March 22, 2002.
Some people are using a digital camera this way, but it's not my favorite way. The old way works well for me. I meter with either a spot or incident meter, take a test picture with Polaroid 54, and then take the actual picture on TMax 100 (my usual film). That way, my test Polaroid shot is >through the same lens and at the same speed/aperture that will actually be used<. Also, the effects of a filter can be seen on the film and that will help decide which filter is best - yellow, orange, red. Color temprature is usually not much of a concern, but just in case of mixed lighting with color film, there is an old Gossen Sixticolor in my kit. Overall, a digital camera weighs less and takes up less room than all my "stuff", but then you lose the advantage of doing your measuring and testing through your actual view camera and lens.
-- Steve Gangi (email@example.com), March 23, 2002.