Use a DSLR to calculate exposure?

[Jon Warwick]

I've started to use a 5x4 camera, mainly using Acros 100 film (given it has minimal reciprocity issues, and I typically photograph architecture at night).

I suddenly thought that maybe it makes sense to use my Digital SLR (a recent one, the Canon 40D) to get an accurate exposure reading. The main benefit that I can see is that I can check a whole load of various exposures on the DSLR's rear viewing screen to chose which one is the best-balanced and the most accurate for the scene in front of me.

I haven't yet had the opportunity to use this "technique" in terms of using whatever exposure appears to produce the most accurate image on my DSLR's rear viewing screen and simply using that shutter & aperture combination on the 5x4.

Does anyone use this "technique"? Does it work in reality, or am I missing something?

[Frank Petronio]

I use a dslr too, I use the histogram mostly to judge the exposure but I also factor in some experience and common sense. I understand that my technique is less than optimal compared to a carefully set-up and controlled Zone System approach using a Densitometer to establish film speed and careful consistent custom development. But I use one type of film (Tri-X) developed consistently but without any customization by a good commercial lab (Praus, www.4photolab.com). And it works just fine. Maybe I am missing the optimal exposure by half a stop but I screwed up that much even back in the day when I had my own darkroom and my official authorized Pentax 1-degree spot meter ;-)

I did rate the Tri-X at 320 and while I do chimp and consider the preview image, I try to discipline myself to value the histogram more than other factors. Still it is nice to see the digital preview to see if you want to push or pull the exposure value for a special treatment of high or low key scenes. I won't use Polaroid anymore since it will soon be impossible to get or too expensive for all but the most important scenes, so I went cold turkey and eliminated it from my workflow.

In any event, you just need to shoot and test, and maybe you adjust your film ISO or fudge some other way.

As far as tonal range, while the dslr may be more limited, the center of the dslr tonal range is usually where I want my film to be too. If the extreme shadows or highlights plug that's usually OK but I can always cheat a stop if I want to be sure to capture one or the other. But that is experience and practice working....

The dslr also helps me decide whether a set-up is worthy and it definitely helps me loosen up portrait subjects. When I switch to the large format camera after shooting with the dslr, my subjects always seem to "rise to the occasion" because they know the big film is special.

Also the Nikon metering is especially good when you are in a hurry...

Of course if you follow the dogma here you absolutely must have a Pentax Digital Spot along with your Chamonix/Arca-Swiss and Schneider 110-XL in order to make a decent photograph ;-)

[roteague]

Does anyone use this "technique"? Does it work in reality, or am I missing something?

I don't find it works well at all. However, I use my Nikon F6 at times as a light meter, Nikon DSLRs tend to underexpose too much. It also allows me to shoot 35mm of the same scene.

[Kirk Gittings]

The only real problem is that proper DSLR exposure, or ETTR (expose to the right, pushing the right shoulder of the histogram as far as you can to the right without clipping the highlights, this approach minimizes shadow noise), is more like shooting chromes (in a general sense) than B&W negatives (expose for the shadows, develop for the highlights, with B&W and a DSLR pin the important deep shadows slightly above clipping on the left and see how far the highlights fall and adjust development accordingly-this involves some experience and some guesswork). So as long as you can switch your brain back and forth between the two paradigms you can do alright. BUT it is not nearly as accurate approach as using a good spot meter and the Zone System or BTZS. To me the approaches are so different that I treat them as distinct paradigms.

[roteague]

BUT it is not nearly as accurate approach as using a good spot meter

That bears repeating ....

[Frank Petronio]

Nothing personal to Kirk or Robert but I disagree that a spot meter is somehow more accurate than a good DSLR. I think they are speaking more out of the large format dogma and tradition here.... If anything the meter of a modern dslr (at least a Nikon) is going to be more sensitive and probably respond in a more even-handed (linear) fashion than a 35-year old Pentax design. As far as measuring light, I think the modern mid-level digicam has to be at least as accurate as a light meter.

I'm not saying that taking an "average" meter reading off a dslr is anymore usable than taking an EV (exposure value units of one stop) value off your Pentax is. But for somebody who is new to this and hasn't gone through the Zone System yet (or ever) it seems to me that his tools are just fine -- it's how you interpret the values the camera or meter gives you. Handing someone a spot meter and knowing the EV without their having a grounding in the theory behind the Zone system doesn't help them make a more accurate exposure.

Use the camera. Shoot a couple of sheets, adjust as needed. It will become second nature if you actually try.... Why waste $300 on a spot meter if you have a more accurate, useful, and versatile tool right at hand?

Besides, most Zone System shooters usually shoot just bright enough to hold the highlights and let the shadows fall where they may, which is relatively simple. I know some of you do pull developments but I bet it is a very small minority.

[gevalia]

I really hope I don't sound like the idiot here but, isn't DSLR ISO completely different then analog ISO? When I started with 4x5 a whopping 6 months ago, I initially used my D80 as a crutch (my term, no offense intended) when I was training myself on the Zone system with my used Luna Pro. I found that in low light situations, that exposure was off between the DSLR and Luna Pro - taking into account reciprocity of course. For me this held true with both Acros 100 (ei 50) and TMAX 400 (ei 200).

Remember, as a beginner, my 2 cents adjusted for inflation are worthless.

[Scott Kathe]

I found that in low light situations, that exposure was off between the DSLR and Luna Pro - taking into account reciprocity of course. For me this held true with both Acros 100 (ei 50) and TMAX 400 (ei 200).

I think you mean the exposure was off when you compare the DSLR image and film shot using the exposure calculated from the LunaPro. The meter in the DSLR and LunaPro should give you the same results. If not the LunaPro could need to be calibrated. The only reason I bring this up is because last year my film was consistently underexposed by about a stop with low light levels and my LunaPro SBC needed to be calibrated. Now it works great!

Secondly, I though Acros 100 had very good long exposure characteristics and you don't have to worry about reciprocity till about 2 minutes.

Scott

[Marko]

I really hope I don't sound like the idiot here but, isn't DSLR ISO completely different then analog ISO? When I started with 4x5 a whopping 6 months ago, I initially used my D80 as a crutch (my term, no offense intended) when I was training myself on the Zone system with my used Luna Pro. I found that in low light situations, that exposure was off between the DSLR and Luna Pro - taking into account reciprocity of course. For me this held true with both Acros 100 (ei 50) and TMAX 400 (ei 200).

Remember, as a beginner, my 2 cents adjusted for inflation are worthless.

ISO is ISO, there's no such thing as "analog" or "digital" ISO.

At the very basic level, both a traditional light meter and a DSLR are built around a light sensitive silicon chip, which is a fairly linear device.

Reciprocity failure, on the other hand, is a "feature" of film.

I see absolutely no reason why a DSLR could not be used as a pretty capable light meter, provided that one knows how to calibrate and use it in the first place. And while at it, it is also a very inexpensive substitute for Polaroids too.

[Ron Bose]

You need to expose a few sheets and learn how to get nicely exposed negatives. To do this you need a consistent meter, IMHO an incident meter is better than a DSLRs TTL Matrix metered 'intelligent' digital sensor optimised meter.

The incident meter doesn't try to compensate, the evaluative matrix metering does, so your readings won't be consistent.

A spot reflective meter is also more consistent 'if you know how to use it'. In other words, you can select an 18% (or 13%) gray item in every one of your images and meter off it.

I know photographers who can meter accurately in their heads, based on the heaviness and length of a shadow. Metering isn't that tricky, but a DSLR tries to think for you and over evaluates and therefore over or under compensates.