DSLR Metering?

[Chan Tran]

When you said the exact exposure that you like, that worries me a bit. Because if you say you use the exact exposure settings on the DSLR that delivers the image that you like on the DSLR then you run into the problem that flying camera is talking about. What I would suggest that to use your DSLR as a spot meter (and not a center weighted or matrix meter). Set the ISO the same as you would if you have a spot meter. Use the aperture and shutter speed indicated as the meter reading. Use that reading as if you got the reading from a spot meter. Since most people don't set the camera exactly the same as the reading on a spot meter you generally shouldn't do that either with the DSLR.

[Steve Smith]

A DSLR can work, but if you do closeup where there's bellows extension, your DSLR won't calculate the compensation.

A light meter won't either.


Steve.

[Chan Tran]

Just a check! I don't have a DSLR (I am an APUGER what do you expect?) so I take out my Nikon F5 which I hope would have a metering system similar to that of a Nikon DSLR. I set it to spot and use an 85mm lens on it. I compare the reading with my Konica Minolta Flashmeter VI in spot mode and the readings are within 1/3 stop from bright sun to indoor light levels. So sure I know that the F5 although much bigger and heavier would certainly works as a reasonable substitute for a hand held spot meter.

[wiltw]

I have tried this before with multiple hand-held meters compared to multiple makes and models of DSLR - specifically a Sekonic 308 and 408, Minolta AutoMeter IV, and Minolta SpotMeter M and Spotmeter F against an Olympus E1, a Canon 30D, Nikon D60, and Canon 5D mk 1. Lighting was studio strobes. The cameras were set to the flash meter reading in Manual exposure mode, with the ISO of the camera set to the same ISO as used by the flash meter. In every case, there was a deviation from proper exposure (either over or under, to varying degrees, as viewed on the camera LCD and on downloaded files viewed at 100% on a calibrated monitor) on the DSLRs when using the meter reading from the hand-held meter. All cameras were set to the lowest ISO available (in most cases ISO 100, in some cases ISO 200). All hand-held meters were calibrated to give the same result under identical controlled lighting conditions. I don't remember which camera was further off the meter reading, or by how much. In some cases it was as little as 1/3 stop, which is close enough for negative film work, and in some cases it was over 1 stop (IIRC the Olympus E1 was the one that was off by more than 1 stop, and since it is largely a dead system, probably irrelevant to everyone today). My point still stands though - a DSLR is not a good match for metering film exposures. The best match is a properly used hand-held meter. If you KNOW the bias of your DSLR and can remember to compensate for it, then it will work. The thing that bugs me about DSLRs is that ISO no longer means ISO - an International Standard... ISO 100 on a Nikon D800 will deviate from ISO 100 on a Canon 5D which will deviate from a Pentax, a Sony, and a Leica. If it isn't consistent, it isn't a standard anymore. They ought to just call it Slowest, Slower, Slow, Medium, Medium Fast, etc, all the way up to Ludicrous Speed.

Our equipment varies:

• Shutters in cameras have frequently deviated from the stated speed.
• Apertures in lenses have frequently deviated from the stated aperture.
• And then there are light transmission differences due to number of optical groups and the quality of the coatings.

People have frequently applied a different Exposure Index to films, differing from the manufacturer speed. Velvia at EI40 rather than ISO50 is a very commonly known example.

And, meters have always used different values of the Constants within the ISO standard equation for incident meters (constant C) and the equation for reflected light meters (constant K).

• With a hemispherical receptor, ISO 2720(1974) recommends a range for C of 320 to 540 with illuminance in lux. Values typically are between 320 (Minolta) and 340 (Sekonic).
  
  N^2/t = ES/C
  
  
• ISO 2720(1974) recommends a range for K of 10.6 to 13.4 with luminance in cd/m². Two values for are in common use: 12.5 (Canon, Nikon, and Sekonic[1]) and 14 (Minolta, Kenko, and Pentax); the difference between the two values is approximately 1/6 EV.
  
  N^2/t = LS/K
  

And the above totally does not factor in long standing discussions of reflected meters calibrated for 18% tonality or 13% tonality!

[Mainecoonmaniac]

A light meter won't either.


Steve.

But an DSLR has a suface area of exposure. So 100% magnification on a small DSLR chip will not be 100% magnification on a 4x5 is an example. Exposure compensation for macro work can be based on magnification.

Also, I wouldn't assume that chimping on an LCD screen will give accurate exposure either. A chip on a digital camera has a different exposure curve than a piece of film.

As other APUGers posted, nothing beats a spot meter and knowing how to use it.

[E.Jensen]

Let me rephrase that last question so it makes more sense to me, if f/11 and 1/125th of a second is the correct exposure for a 35mm piece of film, if i were to put that piece of film into a 4x5 camera(i know it will only be part of the frame) and set the 4x5 to f/11 and 1/125th of a second, removing all other variables, the film should be exposed exactly the same in both cameras, correct?

[Diapositivo]

You don't need to put your camera on the back of your 4x5 as asked in the OP. If the "correct" exposure for the scene you want to photograph is 1/125@f/11, however determined, and you use 1/125@f/11, you'll have the right exposure, bellows factor apart (see below).

If in order to determine your exposure you use a FSLR, or a DSLR, it's enough that you point the FSLR/DSLR to measure the same scene. You don't need the camera to be inside or behind the LF camera. Just have it frame the same scene from roughly the same point of view.

If your goal is to have an "internal" light meter that will take into account the bellows factor of your 4x5, then the answer to your question in #26 I suppose is no (it's 3 am so I'm not sure of anything ).

Suppose you have a bellows factor of 1 stop. Your DSLR at the focal plane, supposing you manage to have it not measure any stray light, tells you 1/125@f/11. As your bellows factor is 1 stop, that means that your LF lens must be set at 1/125@f/8 to give the "correct" exposure that you have determined being 1/125@f/11.

This means that you have to calculate and know in any case the bellows factor, and "factor it" in the exposure calculation, which probably defeats the entire exercise.

If you know the bellows factor, you can take a measure with your DSLR of the scene, use this as your base exposure, compensate it for the bellows factor, and set the compensated exposure on your LF lens.

Fabrizio

[E. von Hoegh]

Let me rephrase that last question so it makes more sense to me, if f/11 and 1/125th of a second is the correct exposure for a 35mm piece of film, if i were to put that piece of film into a 4x5 camera(i know it will only be part of the frame) and set the 4x5 to f/11 and 1/125th of a second, removing all other variables, the film should be exposed exactly the same in both cameras, correct?

Correct. The "f" numbers are a ratio, as a means of setting exposure they are independant of format size and focal length.
But, using a DSLR as a meter is a kludge at best. Treat yourself to a decent handheld meter, it need not cost more than $50. You won't regret it, I promise you.

[David A. Goldfarb]

If you know what you're doing, you can get accurate exposures by a variety of methods--spot metering, incident metering, or by using the internal meter of another camera. You just need to be aware of what the differences are, and what the strengths and weaknesses of each system are. If what you have now is a LF camera and a DSLR, then you can learn to use it to get consistent exposures for now. In general, I'd prefer to use a handheld meter or even rules of thumb and experience, but if you're the sort of photographer who always has both cameras anyway, then it could be more convenient to use the second camera as a meter.

To the person who said they tried it in the studio and were off, I'd guess it was forgetting bellows factor, because at studio subject distances, bellows factor is an issue with 4x5" and larger, but not with 35mm and smaller outside of macro work. If the exposures were with continuous or available light, there was probably also reciprocity, which doesn't seem to be an issue with digital (or daguerreotypes, interestingly enough).

So if you're using a DSLR (directly, not with an adapter on the view camera back--vignetting from the adapter and mirror box will make this a very limited option) or any meter, you calculate the base exposure, then add filter factor, bellows factor, and reciprocity in that order (as a shortcut, if I'm using the same filtration for many shots, I compensate in the ISO setting on the meter). Remember that with color film, reciprocity may also include small adjustments in filtration.

With a DSLR or other camera, you also need to be aware of some differences that can only be determined by testing, like inaccurate shutter speeds and difference in transmissive light loss between the LF lens and the SLR lens.

Another issue is that a DSLR sensor responds like color slide film, and you've got a lot more range with B&W neg film, so if you are shooting B&W, you'll want to use the spot metering setting on your SLR, if you have that option, to determine the brightness range of the scene, to see if you should adjust your development time to get a neg that prints well. If you don't have spot metering, then make some tests and look at the histogram, and learn how to correlate the histogram of the sensor to the histogram of the film, if you were to take readings with a densitometer and plot it. Don't have a densitometer? Then you make judgments like "if I'm just clipping the highlights and shadows in the histogram on the dslr, maybe I should develop -1" or "if the whole curve fits into 1/3 of the histogram space, I should try +2." You can shoot multiple negs, develop to different times, and test this.

If you're using a DSLR as an exposure meter and shooting color, you can fix the white balance on the DSLR to match the film and also use it as a color meter. Handy, eh?

If you want to use the DSLR as a visualizing tool for B&W filtration, and your camera has a B&W setting, shoot T-Max 100 in your LF camera--the spectral sensitivity is a lot like digital.

[Chan Tran]

Correct. The "f" numbers are a ratio, as a means of setting exposure they are independant of format size and focal length.
But, using a DSLR as a meter is a kludge at best. Treat yourself to a decent handheld meter, it need not cost more than $50. You won't regret it, I promise you.

I doubt that a decent spot meter can be had for $50 not even $100. With many meters I actually rather guess at the exposure.