Digital ISO vs film ISO... do they equate?

[Horatio]

I'm just curious to know how close the two really are in terms of obtaining accurate exposure. Could you measure in one and transfer to the other?

 

[juan]

Some people use their digital cameras to determine exposure settings for film. I’ve never done it.

 

[Chan Tran]

Yes they are equal and yes they are all over the places. You can compare 2 film of same ISO or 2 digital cameras set at same ISO and they are not the same.

 

[Auer]

FWIW, I use a Pentax K-5 IIs as a check when I doubt an older cameras meter sometimes, just to see where it's at.
This I do at home inside with a consistent light source.
I dont bring it with me as a "meter".

Also the app on my phone is accurate enough for my type of shooting so when going with a no meter camera that's what I use, or just sunny 16 (mostly).

 

[Mal Paso]

My Nikon Digital is the best meter I have. It maps the entire picture to the sensor. Lots of people use their digital camera to determine their film exposure.
You still have to test your film speed and range in relation to the digital camera.
I find it simpler to use a Pentax Spot to meter areas important to me.

 

[wiltw]

I have two handheld meters, both originally procurred over a decade before digitanl cameras were affordable to the general public. They gave precision results, including for color transparencies exposed for professional purposes. They both match the meter in my digital camera, and exposures taken with handheld meter reading vs. with camera meter readings are not discernable...IOW old film meter readings are fully applicatble to digital exposure. There is only one current ISO standard for photographic purposes and film and digital both follow the same standard.

 

[cowanw]

A couple of interesting sites

https://www.iso.org/popular-standards.html

ISO for film
https://www.iso.org/iso-6-camera-film-speed.html

ISO for digital still- or one of them there are many
https://www.iso.org/obp/ui/#iso:std:iso:12232:ed-3:v1:amd:1:v1:en

discussion. this makes the point that ISO5800:2001 for film is to achieve the negative stage and has no input regarding the positive image (other than the resulting negative). The ISO12232:2019 is to achieve a JPEG of presumed correct brightness.
https://www.dpreview.com/articles/9698391814/the-ins-and-outs-of-iso-what-is-iso

This lists the many different ISO standards for imaging including the different ones for film and digital
https://shotkit.com/iso-standards/#...ies,increasing sensitivity of today's cameras.
At the end of the day- Maybe, mostly, maybe not.

 

[RalphLambrecht]

I'm just curious to know how close the two really are in terms of obtaining accurate exposure. Could you measure in one and transfer to the other?

In principle, Yes, that is possible but,of course, very digital camera an it's sensor have their own native ISO; a value unknown to the owner and assumed by the software engineer of the camera's firmware.that said, measurements with my Gossen lightmeter and my Nikon D800 closely correlate.

 

[Alan Edward Klein]

I checked my Olympus E-PL1 micro 4/3 center metering against my handheld meters and the readings are the same. When I use the E-PL1 as a meter, I check the histogram and the way the picture looks on the screen and then favor the reading for white clipping on chrome shots and shadow clipping on negative film shooting.

An issue with digital camera metering is you want a camera that allows you to stop down. My E-PL1 I can set the smallest at f/22 which I use when shooting 4x5. But many small digital cameras (P&Ss) only stop down to let's say f8. So it becomes more difficult to find the setting you want.

I also use the camera in BW mode when shooting BW film. I use the viewfinder screen to select the shot before setting up the camera location. Saves a lot of shoe wear. Also, I use its zoom lens to determine the fixed lens to select on my large format camera. I'll also record my settings and the view using video mode for transcription later.

 

[Chan Tran]

I checked my Olympus E-PL1 micro 4/3 center metering against my handheld meters and the readings are the same. When I use the E-PL1 as a meter, I check the histogram and the way the picture looks on the screen and then favor the reading for white clipping on chrome shots and shadow clipping on negative film shooting.

An issue with digital camera metering is you want a camera that allows you to stop down. My E-PL1 I can set the smallest at f/22 which I use when shooting 4x5. But many small digital cameras (P&Ss) only stop down to let's say f8. So it becomes more difficult to find the setting you want.

I also use the camera in BW mode when shooting BW film. I use the viewfinder screen to select the shot before setting up the camera location. Saves a lot of shoe wear. Also, I use its zoom lens to determine the fixed lens to select on my large format camera. I'll also record my settings and the view using video mode for transcription later.

Alan! If you check the meters of most digital cameras and your hand held meter designed for film I am quite sure they are in agreements. However if you take pictures with different digital cameras at the same ISO setting you will find the result are not the same. In other word the meters of most cameras would tell them to expose the same way but the results are different.

 

[Paul Howell]

My Konica Minolta, Sony, Pentax, and Sigma digital cameras are within a 1/2 stop of my Gossen and Weston IV and match my Minolta 9, 7, and 800si. I have used and use my Pentax or Sigma SD 10 as meters for film, most useful in that regard is the Sigma in Matrix mode.

 

[Chan Tran]

My Konica Minolta, Sony, Pentax, and Sigma digital cameras are within a 1/2 stop of my Gossen and Weston IV and match my Minolta 9, 7, and 800si. I have used and use my Pentax or Sigma SD 10 as meters for film, most useful in that regard is the Sigma in Matrix mode.

Yup! The meters are calibrated pretty much the same but the ISO isn't.

 

[wiltw]

You might want to read more deeply about this topic before you spout absolutes like this.

OK I oversimplified

• There is one ISO standard for meter calibration
• The is another ISO standard for film speed rating (vs the meter reading
• There is another ISO standard for digital image brightness (vs the meter reading)

Mea culpa
The triumvirate above makes film density come out same as digital camera sensitivity and response being virtually 'the same'.
Why one meter reating equates to 'proper exposure', regardless of film vs. sensor

 

[Alan Edward Klein]

Yup! The meters are calibrated pretty much the same but the ISO isn't.

I don't understand your point. If I use a handheld meter set for ISO 400, it will give me a specific reading. Whether I set that on a digital camera or film camera doesn't;t seem to matter. How would it? The meter doesn't know what I'm shooting.

 

[Chan Tran]

I don't understand your point. If I use a handheld meter set for ISO 400, it will give me a specific reading. Whether I set that on a digital camera or film camera doesn't;t seem to matter. How would it? The meter doesn't know what I'm shooting.

I meant most of the meters including the ones in digital cameras and hand held are pretty much the same. They don't give different reading but if for example you set 2 digital cameras to ISO 400, same aperture, same shutter speed and takes the pictures you wouldn't have 2 pictures of the same brightness. So the ISO 400 for 1 digital camera isn't the same as ISO 400 for the others.

 

[wiltw]

I meant most of the meters including the ones in digital cameras and hand held are pretty much the same. They don't give different reading but if for example you set 2 digital cameras to ISO 400, same aperture, same shutter speed and takes the pictures you wouldn't have 2 pictures of the same brightness. So the ISO 400 for 1 digital camera isn't the same as ISO 400 for the others.

The problem with your assumption is NOT about two camera meters that see only a uniform area show different readings! The meter calibration standard makes them all conform within less that 1/3EV.

The problem with your assumption is that two digital camera meters in the Evaluative metering mode are programmed to interpret the different zones in the frame, and to bias some specific zones, and you have no idea how the eingineers designed that matrix metering to behave!
Matix metering got this entirely wrong, even when I focused on the grey card itself it was not exposed properly!

 

[Chan Tran]

The problem with your assumption is NOT than two cameras that see only a uniform area show different readings!
The problem with your assumption is that two digital camera meters in the Evaluative metering mode are programmed to interpret the different zones in the frame, and to bias some specific zones, and you have no idea how the eingineers designed that matrix metering to behave!
Matix metering got this entirely wrong, even when I focused on the grey card itself it was not exposed properly!

Forget about the meters. Set 2 cameras on the same ISO, shutter speed and aperture and see if they produce identical results? They don't.

 

[grat]

You might want to read more deeply about this topic before you spout absolutes like this.

Actually, he's kind of right. They're two different documents, one for film, and one for digital sensors, but the general gist that doubling the ISO should double the sensitivity is the same, and the relationship between EV, aperture, shutter, and ISO speed remain the same.

The problem is the results-- there's one standard for analyzing the resultant film negative, and a totally different one that basically says "we're trusting the manufacturers" for digital sensors-- which kind of makes sense, because different sensors respond in different ways.

They *are* supposed to be equivalent, and an exposure of f/5.6 for 1/60th of a second on ISO 100 (EV 11) film should produce a similar result to f/5.6 for 1/60th of a second on a digital camera set to ISO 100.

But it might not.

 

[wiltw]

Forget about the meters. Set 2 cameras on the same ISO, shutter speed and aperture and see if they produce identical results? They don't.

Three shots all ISO 400, 1/200 f/2.2, using same lens for all 3 bodies, shot RAW and imported to Lightroom with no postprocessing alteration. left to right, 7DII, 5D, and 40D

The 5D shows lens vignetting, which is not seen in the smaller frames of the 7DII or 40D.
The 5D shows evidence of what was revealed in reviews at the time: "The 5D shows about 1/3EV greater sensitivity than the rating.". In the later models this deviation was eliminated.
Basically both the 7DII and 40D inherent density of frame area matches the mid-tone background surround that is used by LR...and those two frames MATCH for density, as can be shown with LR's eyedropper display density values in R-G-B values!
You said to ignore the meters re: difference, but all three meters matched, too.

If you tried the same thing with 3 film cameras, you have the variable of same lens not fitting all 3 bodies, so is each lens' aperture identical? And is each film body's mechanical shutter accurate (or match the electronically timed shutter).?

 

[Warm Winter]

Can you transfer? Usually. Mostly. They're sort of the same.
The short answer is the basic exposure settings may transfer but the curves and responses of a digital sensor and a film can differ in how they render color/contrast (say, log curves for color in cine usage) plus the possible dynamic range.
And then sensors have their own base ISO which might make things potentially weirder in some cameras if you try and meter on a digital camera with a super high or low ISO for some reason.
If anything it'd be almost better to think of a digital sensor in terms of gain vs the base ISO instead of using speeds. +3Db would be a doubling of the sensor ISO but also transfer more generically to film possibly.
ISO on digital sensors is more for, well, photographers as we're sued to thinking in ISO. Broadcast typically uses Db since they started as analog electronics (thus, gain values) and broadcast people are used to thinking in Db and gain because of it. Photography speed ratings were ASA/DIN/ISO before electronic capture was even attempted so it's in what we're used to.

That said, how digital sensors see the world and the sampling theory would both be rather intense and in depth subjects that have books written on them so there isn't much of a super clean answer that will universally apply.

 

[grat]

@wiltw: I'm surprised the 40D wasn't a bit off-- I know my 30D had the same +1/3 stop offset as well. Always shot with exposure compensation enabled.

 

[wiltw]

@wiltw: I'm surprised the 40D wasn't a bit off-- I know my 30D had the same +1/3 stop offset as well. Always shot with exposure compensation enabled.

Well, Canon 'fixed' a number of things in releasing the 40D, vs. things found in 20D or 30D, such as

• Accuracy of ISO rating, sensor sensitivity vs. rating
• Underexposing of eTTL flash shots, in which flash is primary source of illumination

 

[grat]

And then for the 60D, they "fixed" the joystick by removing it.

I'd thought they made the change to the ISO rating on a later model. I literally bought my 30D about 2 weeks before the 40D hit, so I mostly ignored the 40D.

 

[wiltw]

And then for the 60D, they "fixed" the joystick by removing it.

I'd thought they made the change to the ISO rating on a later model. I literally bought my 30D about 2 weeks before the 40D hit, so I mostly ignored the 40D.

I was so glad to find that the 40D no longer needed FEC = +1 as a standard setting, for eTTL flash exposure to be 'correct exposure' and exhibit same level of brightness as an ambient-only shot! I never really paid much attention to deviation from rated ISO, so the 40D did not catch my attention in that regard (vs. its older brothers)

Yeah, when the 7D series came out, Canon emasculated the status of the nnD line so it was no longer 'prosumer' in their categorization, the line became 'fancy Rebels' in that regard, losing joystick and PC connector terminal, and I forget what else they consider 'not needed for amateurs'.

 

[grat]

Yeah, when the 7D series came out, Canon emasculated the status of the nnD line so it was no longer 'prosumer' in their categorization, the line became 'fancy Rebels' in that regard, losing joystick and PC connector terminal, and I forget what else they consider 'not needed for amateurs'.

The 90D restored the joystick at least. Pity it's probably the last APS-C DSLR from Canon. I just can't wrap my brain around an EVF, so I don't know if I'll ever get a mirrorless ILC, unless it's modified for IR work.