Using a DSLR as a meter

[Brian Ellis]

"Try the following experiment with your camera. Place your camera on a tripod. Evenly light a test pattern like a step wedge. This will give you a subject with a known long tonality range. Now set your contrast to minimum. Shoot an image and note the histogram on the camera. Note how close the maximum step and the minimum step of the step wedge are apart on the histogram. Now set the contrast to maximum. Repeat the experiment. You will now find that the minimum and maximum steps in the wedge are off scale to the right and left. Now open the two images in your RAW image processor on your computer. You will now see that the two histograms displayed by your processing software are the same. The contrast setting had no affect (sic) on the RAW file.

What does all this mean? In order to display the full dynamic range of your camera in the histogram displayed on the back, you must set the contrast to minimum. You now can see the same dynamic range in the histogram on the camera as you will see it in your RAW processor on your computer.

When shooting RAW always set the contrast to minimum so that the histogram displays the full dynamic range the camera can capture. This makes for rather dull images on the back of your camera, but gives you better information about exposure and clipping."

O.K., I feel like a dunce but I'll ask the question anyhow. What's he mean when he says "set the contrast to minimum" and "set the contrast to maximum?" I don't offhand remember ever "setting the contrast" on any camera. The contrast of the scene is what it is. Does he have some special camera that I've never heard of or is he using different terminology for something we routinely do or what?

[Kirk Gittings]

Brian, he is talking about the Jpeg rendering on the camera screen and accompanying histogram by adjusting the "picture style" settings in the camera. I think you have 5DII? It is in the picture style menu.

[Brian Ellis]

Brian, he is talking about the Jpeg rendering on the camera screen and accompanying histogram by adjusting the "picture style" settings in the camera. I think you have 5DII? It is in the picture style menu.

Ah, thanks Kirk. I never use the picture styles so I don't know anything about them, I've always just used manual or aperture preferred. I'll have to check them out.

[Dr Bellows]

I've used my Canon S45 as a meter in the past, with good results. When lazy, I just set it to automatic, take a test photo and if it looks good, use the exposure indicated by the camera. When less lazy, I set the camera to spot metering and evaluate shadow and high values to come up with an exposure for my 4x5. I write the digital camera's photo number on my 4x5 exposure record for reference.

When I shoot with a filter, my digital test shot is done trough the same filter to see how it looks and to compensate for filter factor. This is a real help for B&W through colored filters.

I have yet to use a DSLR for this purpose due to weight and space. I plan a National Park trip soon and that will pose a dilemma. There's no way I'm leaving the 4x5 home, but I would also like to bring the DSLR since it is more flexible and makes better photos than the compact camera. I'm trying to coax a friend that shoots the same brand of DSLR to join me so we can share lenses. Since I can't talk any of my friends into winter backpacking, it turns into day hikes anyways, so the weight is never too bad, but space may require the full-frame pack.

[Jerry Kaiser]

I shoot 8x10 so the film and developing adds up fast. I use my Nikon DSLR on manual modes to take my spot meter readings and set up a digital shot. I then bracket with the digital and use the camera screen and other options to pick which of the bracketed digital pics I like best. Then I cross that back to the spot meter dials and then take the readings off the spot meter for my LF lens.

Example: I lock the Nikon to ISO 100 since that is the film I use; I take a spot meter reading (say 14 for this example);then you have to know about how much F-stop you want for your LF shot (so say I want my LF shot at near max of f-64 which gives a shutter of 1/4 second); then I manually set the Nikon to near max of f-22 which gives a shutter of 1/30 of a second (all using the dials on the spot meter setting of 14). Then I bracket the shot by adjusting shutter or f-stop depending on the end result I am chasing for the film; I pick the best picture from the back of the camera, look at histograms, check for any overexposures, etc; I then look at the settings on the Nikon for that shot (say I chose f-22 at 1/45 of a second); then by setting the spot meter dials with these settings it it shows an equivalent spot meter reading of about 14.5; then you can see the settings for the LF the usual way and shoot 1 picture instead of 2 or 3. This works really well for me and the film/developing savings have paid for the Nikon a long time ago.

Things like the amount of F-stop, desired shutter speed range, focus, etc that you want your film to be exposed to, are still from experience. All the DSLR does is help you stop bracketing with film or even avoiding taking a shot sometimes. I also compose the picture sometimes using the DSLR if I am in a hurry or not sure if I really want to shoot or not. You just need to know where to set the DSLR zoom to make the field of view similar to the lens on your LF camera and then you can look at the picture composition on the back screen of the DSLR.

Hope this is clear, if not email me. Jer

[Alan Davenport]

I'm amazed anyone ever got a decent exposure before there were histograms. A histogram is nothing but an artifact of the digital processing of the image; it tells you nothing you can't get from a meter.

For transparencies, pick the brightest part of the scene where you need to retain detail on the film and meter that area. Set your exposure to 1-2/3 or 2 stops more than the metered value (you'll have determined in advance how much difference to allow) and make the shot. Voila, no blown highlights.

Use an analog meter. They're more precise.

[Robert Hughes]

I'm amazed anyone ever got a decent exposure before there were histograms...
Use an analog meter. They're more precise.

Imagine that people got decent photographs before meters, ISO ratings, or any of that fancy 20th Century stuff. Tell it to Mr. Brady...

Sunny 16 works as well as it ever did.

[Marko]

I'm amazed anyone ever got a decent exposure before there were histograms. A histogram is nothing but an artifact of the digital processing of the image; it tells you nothing you can't get from a meter.

For transparencies, pick the brightest part of the scene where you need to retain detail on the film and meter that area. Set your exposure to 1-2/3 or 2 stops more than the metered value (you'll have determined in advance how much difference to allow) and make the shot. Voila, no blown highlights.

Use an analog meter. They're more precise.

No they aren't. A DSLR you own will trump any light meter you don't own. Which is a number one reason why people keep asking this question.

A histogram can tell you much more than a simple needle on a light meter if you bother to learn how to interpret it. Calling it an artifact is simply ignorant.

I own both and use a spotmeter for LF most of the time. If I didn't have one or couldn't afford one, I could (did) get along just fine without it.

No need for bloviations about good old times being ruined by evil new technology. It's getting really old, to the point of becoming demented. And even the technology in question is not exactly new any more either.

[Alan Davenport]

A histogram can tell you much more than a simple needle on a light meter if you bother to learn how to interpret it. Calling it an artifact is simply ignorant.

Your histogram is an artifact of the processed image that was created by your digital camera, using responses programmed into its processor. When you consult the histogram, you aren't measuring the original scene; you're just seeing what resulted from the processing done in-camera. That's an artifact.

I'm not saying that DSLRs don't make serviceable light meters, but it's delusional to believe digital technology is somehow required to make 100 year old film technology work to its best effect.

[Jack Dahlgren]

Alan,

The movement of the needle or display is just an artifact of the processed photons in your lightmeter using responses programmed into its processor (or by current passing through a coil made by someone somewhere). When you consult the light meter you aren't measuring the original scene, you're just seeing what resulted from the processing done in-lightmeter. That's an artifact.

No one is saying is a DSLR necessary to make film work to best effect. It is delusional to think that someone would insist that digital technology is somehow required to make 100 year old film technology work to its best effect.