Using a digital camera as a light meter to shoot film

[Alan Edward Klein]

This assumes that the difference is both consistent and linear.
You need to check at a variety of different light levels, and make sure you are reading the same area.

Why would they be differnt on a camera meter but not on a hand held meter? Do you know this for sure? Or are you assuming a possibility?

 

[BrianShaw]

Why would they be differnt on a camera meter but not on a hand held meter? Do you know this for sure? Or are you assuming a possibility?

It would be a Herculean task to find it, but I recall an extensive discussion on that in the past. Lots of information and emotion. There may have also been some data.

 

[Alan Edward Klein]

It would be a Herculean task to find it, but I recall an extensive discussion on that in the past. Lots of information and emotion. There may have also been some data.

If readings aren't consistent and linear in a camera, how would a photographer ever know how to adjust for filters? Let's say he puts on a two-stop ND. If the exposure shift in a camera operates in a nonlinear way, then it might be another adjustment other than adding two stops of exposure. Which cameras require that?

Additionally, the f stop and camera speed setting must translate exactly to a handheld meter. Otherwise, you'd never be able to use a handheld to set the settings on the camera. All those expensive spot meters would be useless. Manual readjustments would have to be made after every reading. No camera that I know requires that. It would defeat the whole purpose of standards, stops, etc in the camera industry. If a meter reads 1/4 sec at f/11 then all cameras have to read 1/4 sec at f/11 if it's reading the same subject. Am I missing something?

 

[BrianShaw]

I seem to recall the bulk of the prior discussion revolving around differences in the use of the term ISO. The number might mean one thing in the film world but something slightly different in digital world. Vague recollection, though.

I would expect reasonable linearity with each camera and meter.

 

[jeffreyg]

There is an app for your phone Pocket Light Meter. Dial in the ISO of your film and either the shutter speed or f stop. Lighter and more convenient than carrying an extra camera and the gps can record the location if you also take a picture with the phone. I use a hand-held meter but the app is a backup and the gps saves the trouble of taking notes.

httpp://www.jeffreyglasser.com/

http://www.sculptureandphotography.com/

 

[markjwyatt]

I wonder if there is some benefit to using a Fujifilm APS-C camera for this purpose with its somewhat accurate film simulations? There is a possibility to change the film curve a little also (on both ends). The power of this method is as @Alan Edward Klein half jokingly mentioned it is like having a spectrum analyzer. You can see the full (jpeg- i.e. already reduced dynamic range) histogram. With some judgement you could guess where the highlights and lowlights are, and maybe if probing were possible in the scene (not sure with the XT-2 for instance), you could place some tonal values on the histogram. Even if you needed to create an offset as a calibration to match film to sensor output (say +/13 stop, etc.) this could be done and the histogram will shift.

 

[DMJ]

I think you meant it would be in the film's range. That makes sense. The Olympus has a dynamic range DR of between 7 and 10 depending Assuming film is less, then if clipping shows on the digital camera's histogram, it might not be apparent on film. So my lowering the exposure setting a half of a stop if it does show clipping is just a safe measure.

Yes, it would be in the film range but I was trying to say that there is a loss in dynamic range in the jpeg that the LCD uses for previewing the image. Here is an article about it:

https://clarkvision.com/articles/raw.versus.jpeg1/

I wish digital cameras had an intensity waveform scope in addition to the histogram. I don't own one now and I think those Olympus M43 with tilt screens are great for this. Maybe there is an app that can do aspect ratio, focal length, b&w, histogram and scope in real time.

 

[Alan Edward Klein]

I seem to recall the bulk of the prior discussion revolving around differences in the use of the term ISO. The number might mean one thing in the film world but something slightly different in digital world. Vague recollection, though.

I would expect reasonable linearity with each camera and meter.

Funny, I seem to recall something about that too. But, in fairness to the camera manufacturers, if ISO didn't match the industry standard, how would anyone use a handheld meter to meter? The thing I recall is that there are differing opinions on which ISO level creates too much noise. Each manufacturer decides in their opinion how much noise is too much that could be different between ISO's of two cameras.

It's like trying to assess DOF. You'll get different ranges depending on how big the CIrcle of Confusion COC is. Each manufacturer decides its own which then creates different tables and ranges in the specifications for the lenses.

 

[Alan Edward Klein]

I wonder if there is some benefit to using a Fujifilm APS-C camera for this purpose with its somewhat accurate film simulations? There is a possibility to change the film curve a little also (on both ends. The power of this method is as @Alan Edward Klein half jokingly mentioned it is like having a spectrum analyzer. You can see the full (jpeg- i.e. already reduced dynamic range) histogram. With some judgement you could guess where the highlights and lowlights are, and maybe if probing were possible in the scene (not sure with the XT-2 for instance), you could place some tonal values on the histogram. Even if you needed to create an offset as a calibration to match film to sensor output (say +/13 stop, etc.) this could be done and the histogram will shift.

I don;t think the Fujifilm changes the number of stops of the picture it captures so you can try to match the number of stops of the film. That would be great if you could. The film presets probably are created by the camera;s program editing the raw data.

What I have thought about is why light meter manufacturers don't add histograms to their meters where you can also set the range to the stops of the film. Then you can see exactly where everything is and what's clipping. That would be a huge selling point for them. I think many digital camera users would even find that useful. Certainly, we film buffs would.

Here's another one. Why don't digital camera mfrs show the zones on the viewfinder so you can see immediately where each zone is. That would really be handy for us film people.

 

[Alan Edward Klein]

I did a photo shoot using two digital cameras (Fuji and Canon DSLR) and two film cameras with different emulsions (35mm Delta 100 and HP5+ in 120). Both digital cameras were giving me the same reading from their evaluative meters, and I transferred that to the film bodies.

I do not have the permission from the model to share those images, but if I were to show you 1000px wide scans you won't be able to tell them apart. Same exposure, same look, same everything. Zero difference in metering, and zero observable difference between film and digital (grain is absent at a small magnification).

That's a confidence builder. What's your opinion about the clipping angle between what's on the histogram and relating that to the film?

 

[MattKing]

Why would they be differnt on a camera meter but not on a hand held meter? Do you know this for sure? Or are you assuming a possibility?

The concern relates to whether the meter in the camera is customized to that camera, including the sensor and the firmware and, in some cases (e.g. fixed lens cameras), the lens.
A hand meter is designed to be used with every camera possible. The meters, and the firmware and the sensors in the digital cameras are designed to work in that camera.
Many of us have encountered and probably used the adjustments built into post-processing software that are designed to compensate for distortion and vignetting in various lenses. How do you know that there aren't similar adjustments for non-linear behavior of sensors built into the metering systems of the digital camera you are using?
This is relatively easy to check. Compare the readings - digital camera vs. known reliable hand meter or film camera meter - over a wide variety of conditions, and for a wide variety of shutter speed and aperture settings - and see if they match or merely require an ISO offset. If so, fine. If the variance is non-linear, it is a problem.

 

[wiltw]

There are STANDARDIZED EQUATIONS for characterizing the responses of light meters...the standard make ZERO differentiation between 'for film' vs. 'for digital' meters in cameras, or for handheld vs 'in camera' meters. The only differentiation is 'incident' vs. 'reflected' measurement.

 

[BrianShaw]

I could be wrong but I don’t think exact correlation between film and digital is a major requirement of digital camera engineering. And I doubt that use as a light meter or film visualization tool is either. Not that those aren’t a good idea, of course.

 

[BrianShaw]

There are STANDARDIZED EQUATIONS for characterizing the responses of light meters...the standard make ZERO differentiation between 'for film' vs. 'for digital' meters in cameras, or for handheld vs 'in camera' meters. The only differentiation is 'incident' vs. 'reflected' measurement.

Agree… but I thin the issue I’m recalling is that, for example, ISO 400 means ISO 400, but digital ISO 400 is believed by some to be “something akin to ISO400”. Again… vague recollection of a long-ago highly detailed and emotional discussion that I was watching mostly for amusement.

 

[wiltw]

Agree… but I thin the issue I’m recalling is that, for example, ISO 400 means ISO 400, but digital ISO 400 is believed by some to be “something akin to ISO400”. Again… vague recollection of a long-ago highly detailed and emotional discussion that I was watching mostly for amusement.

Early on in the history of digital cameras, some (few) models were noted to not be precise in adherence to ISO ratings, so were described accordingly. That was more the sensor response rather than the meter response, though. But such deviations disappeared from descriptions of digital cameras.

 

[DMJ]

If you have 3 minutes:

https://www.iso.org/news/ref2375.html

 

[Chan Tran]

The concern relates to whether the meter in the camera is customized to that camera, including the sensor and the firmware and, in some cases (e.g. fixed lens cameras), the lens.
A hand meter is designed to be used with every camera possible. The meters, and the firmware and the sensors in the digital cameras are designed to work in that camera.
Many of us have encountered and probably used the adjustments built into post-processing software that are designed to compensate for distortion and vignetting in various lenses. How do you know that there aren't similar adjustments for non-linear behavior of sensors built into the metering systems of the digital camera you are using?
This is relatively easy to check. Compare the readings - digital camera vs. known reliable hand meter or film camera meter - over a wide variety of conditions, and for a wide variety of shutter speed and aperture settings - and see if they match or merely require an ISO offset. If so, fine. If the variance is non-linear, it is a problem.

I do not think the meter is adjusted to match the imaging sensor in the camera. They are very much the same as the hand held meter except for the Matrix or Evaluative mode which no hand held meter I know of has. And each manufacturer would have the matrix or evaluative meter work differently.

 

[Alan Edward Klein]

The concern relates to whether the meter in the camera is customized to that camera, including the sensor and the firmware and, in some cases (e.g. fixed lens cameras), the lens.
A hand meter is designed to be used with every camera possible. The meters, and the firmware and the sensors in the digital cameras are designed to work in that camera.
Many of us have encountered and probably used the adjustments built into post-processing software that are designed to compensate for distortion and vignetting in various lenses. How do you know that there aren't similar adjustments for non-linear behavior of sensors built into the metering systems of the digital camera you are using?
This is relatively easy to check. Compare the readings - digital camera vs. known reliable hand meter or film camera meter - over a wide variety of conditions, and for a wide variety of shutter speed and aperture settings - and see if they match or merely require an ISO offset. If so, fine. If the variance is non-linear, it is a problem.

Matt, I don't know. You're the one who made the claim but provided no proof or articles. In any case, even if the sensors are non-linear, the camera's program adjusts for it as post-processing programs adjust for vignetting. It's the only way to get exposure readings and settings to follow industry standards. Otherwise, the photographer would not be able to make filter adjustments or use handheld meters. Who would buy a camera like that?

 

[Alan Edward Klein]

I could be wrong but I don’t think exact correlation between film and digital is a major requirement of digital camera engineering. And I doubt that use as a light meter or film visualization tool is either. Not that those aren’t a good idea, of course.

As I stated, at least for exposure, there has to be a standard. Otherwise f stops on lenses, shutter speed stops in cameras, films, ISO, filter, grads, etc. would never be able to be swapped or cross-correlated between any camera. Can you imagine if each film manufacturer used different standards for ISO. Same with digital camera and meters. No one would know what exposure settings they should select. We'd all be in the dark, no pun intended.

 

[Alan Edward Klein]

If you have 3 minutes:

https://www.iso.org/news/ref2375.html

I think it would be polite for you to sum up in ten words the point you're trying to make? Thnaks.

 

[Alan Edward Klein]

I do not think the meter is adjusted to match the imaging sensor in the camera. They are very much the same as the hand held meter except for the Matrix or Evaluative mode which no hand held meter I know of has. And each manufacturer would have the matrix or evaluative meter work differently.

Well hand meters work the same way. You get a different reading depending on where you point it or the angle it's reading. Metering is actually easy. Once you know where to point it.

 

[BrianShaw]

Well, except that in meters there can be differences based on constants, K and C, while still conforming to the standard.

 

[Alan Edward Klein]

Alan, I am not 100% sure I understand the question, and I do not use the histogram when shooting digital. TBH I was expecting my digital cameras to meter for the highlights to protect them, and I was surprised by not seeing that behavior. On the other hand, that was just one isolated example: the studio setup with a limited dynamic range but the model had a bright shirt - that was the only mild metering challenge. Perhaps I would have gotten different results with more complicated lighting.

Well, let's say the camera has a dynamic range of 10.2 stops as my digital camera that I use as a light meter has. However, Velvia 50 chrome has about 4 maybe 5 stops of dynamic range. So it's easy to clip film. So now I check a scene and the meter in the digital camera shows white are clipping. However, since film is different. that doesn't necessarily mean that the film will clip, or does it?

I;m trying to correlate the clipping shown on the digital camera meter to determine if I;m clipping with the film at the same exposure setting. Does the correlation hold true to both or do I have to make an offset to the exposure with the film camera?

I hope that's clear.

 

[Alan Edward Klein]

Well, except that in meters there can be differences based on constants, K and C, while still conforming to the standard.

What does that mean? I don't know what those constants are.

 

[DMJ]

I think it would be polite for you to sum up in ten words the point you're trying to make? Thnaks.

Ok Alan, allow me to be polite. It is a very short article issued by the same people who write the ISO standards. To add to what @wiltw already said I quote from the main document (ISO 12232):

"This document was designed to harmonize with earlier standards developed for film-based photography. For example, the equations were chosen so that using a particular EI on a DSC should
result in approximately the same camera exposure settings, and resulting focal plane exposures, as would be obtained using the same EI on a photographic film camera. For example, the value of 10 as ISO 12232:2019 the constant in Formula (1) of this document is consistent with ISO 2721, so as to harmonize with this earlier ISO standard for photographic film cameras. ISO 2721 uses the term nominal exposure and assumes that the nominal exposure is an arithmetic mean exposure value, which usually corresponds to the mid-tone in photographs of average scenes."