exposure issues using a DSLR as a lightmeter

[Andrea Gazzoni]

I found myself using a Canon 5D MarkII as a lightmeter during a recent trip.
When the film came back from the lab, I discovered that almost every exposure (expired Velvia 100F) was off by 1 to 2 stops.
First guess was bad film.
Second guess bad chemistry at the lab.
So I've done some other tests a few days ago, by loading two film holders with both fresh and expired film.
Shot some 120 rolls too.
Still used my DSLR readings (settings "neutralized"), transferred them to the view camera, and...
both new and old film are still badly underexposed.
The digital shots are ok.

I've already done this before with a $150 compact digital camera, all went fine.

Any suggestion? Except using a dedicated spotmeter...mine needs to be calibrated

thanks
Andrea

[Light Guru]

Well a couple of things come to mind.

First of you are shooting expired film. This alone could cause various issues in exposure.

Second many film photographers don't actually shoot shoot film at the speed listed on the box. Form example I like to shoot most ISO 100 films at ISO 50. But because every film type is different testing is required to find out what ISO a certain film pro forms best at for you.

[Andrea Gazzoni]

really could a 2 years expired film, always kept in the freezer, loose as much as one stop of sensibility?
this has never happened before to me

any difference between say F22 1 sec on a DSLR and the same reading applied on the view camera, right?

[vinny]

use the $150 digicam and throw the dslr away.
sell the dslr and buy a new meter.
two year exp fuji won't lose speed that way. I routinely shoot stuff that's 10+ yrs expired with zero issues.

[Light Guru]

really could a 2 years expired film, always kept in the freezer, loose as much as one stop of sensibility?
this has never happened before to me

any difference between say F22 1 sec on a DSLR and the same reading applied on the view camera, right?

2 years expired probably not depending on how it's been stored but you never said how expired in your original post so ass far as anybody knew it was 5 or 10 years expired.

A 1 second exposure on digital could definitely be different on film. Film has reciprocity failure with times of a second or longer digital does not have reciprocity failure.

But also like I said in my last post many don't actually shoot ISO 100 film at ISO 100 they rate it lower by doing testing.

Also you should know that slide film has an extremely low tolerance for not being exposed right. Expecting your first couple sheets or rolls to be perfect is probably not going to happen you need to learn how that particular film type behaves and shoot accordingly.

[paulr]

DSLRs' actual ISO rating usually differs from the nominal one. Here's (http://www.dxomark.com/Cameras/Camera-Sensor-Database/Canon/EOS-5D-Mark-II#tabs-2) a chart for your camera. It's not off by as much as you're reporting, but this could be part of the issue. So could the difference between the t-stops of the dslr lens and the LF lens.

[mdarnton]

I've noticed that I'm much more satisfied with the way underexposed shots look on the back of my DSLR than they do on film. I get something I like on the camera, and invariably the histogram is way to the left. I guess, then, if I were going to use the camera as a meter, I'd work for a centered histogram, rather than a nice look on the preview. How do the histograms for the "metering" look, if you still have those?

[Leigh]

A DSLR is NOT an exposure meter.

It's a system, of which the exposure analysis is one component.

- Leigh

[David_Senesac]

I would try calibrating the DSLR meter against the compact digital meter by framing the same subjects from same location, using the same exposure frame modes. Make some digital captures and review captures with full screen information. If that shows something off then get more basic and frame something nearby all the same color like a wall or even a grey scale card. If that is still off then one of the camera meters, probably the DSLR is doing something wrong or is in a mode you are not aware of. Of course be sure the DSLR exposure meter is not in spot metering mode. Generally evaluating readings from any meter whether in a dedicated lightmeter or within a camera needs to be done suspicously with an understanding they will vary quite a bit depending on mode and where they are pointing.

I've been using my Canon G10 more for evaluating exposure EV values besides my lightmeter before exposing Provia in dim conditions. So far it seems to be in the ball park versus readings with my lightmeter but I really don't trust it enough yet across all light levels. In other words just because it reads what I'd expect in late morning sunny front lit conditions doesn't convince me that it will also do so at lower levels of the scale in dim cloudy conditions.

I just went outside at 3pm PST on this clear sunny November SF Bay Area day with the sun altitude about 30 degrees. I took an image from a few feet away of a bright light tan wood wall, aperture at f8.0 ISO 100 exposure compensation 0. with the resulting Av mode shutter speed 1/320 second. That is about EV14.5. Image came out ok as expected.

I then pointed my Polaris lightmeter in Incident mode directly at the sun that read EV14.6. This is also my preferred method of evaluating landscape lightning and tend to then expose film about a half stop below. Then changed to 5 degree Reflective mode and read EV15.6 pointing at the subject wood wall which is about what to expect on a bright light subject versus Incident mode. Though not as high an EV as pointing at a white wall. Image came out ok as expected.

Then framed a more neutral subject and had to change the exposure compensation to -1/3 in order to get a reasonable result. Shutter speed showed 1/240 second or EV13.9. All these values were about what I would expect. If I was exposing a sheet of Provia 100F, just from the Incident reading of the sun would probably set my exposure to EV14.1 that is pretty close to what the G10 showed.

[Nathan Potter]

Using the DSLR as an exposure meter can work fine. You just need to determine your own ISO value for the film you wish to use. This is done by simply following a standard zone system procedure for the film calibration. See any number of books on the subject.

Nate Potter, Austin TX. Holliston MA.

[John Olsen]

My sympathies on this. Sometimes the digi-camera is a great guide but often it's misleading. For one thing, my Nikon D90 has an overbright display. So when I use it I tend to get an underexposed film image. Reducing the LCD screen brightness helps. The other difficulty is that I'll view the LCD in a sunny environment or a dim studio and get different impressions of how bright the image is. After several disappointments I've arrived at a recipe of giving my film 1/2 to 2/3 stop more light than my D90 indicates I should need. Usually this works. Mainly, I trust the digital camera to help me get studio lights correct, and then bracket for safety. Outdoors I just trust my spotmeter and leave the digi-crap at home. Remember using Polaroid film? It was a hassle, but totally reliable.

[Jody_S]

I've used a dSLR as a light meter for LF before, but only when using studio flashes, and I didn't go by the image on the LCD panel. I used the histogram.

[Kirk Gittings]

I've used a dSLR as a light meter for LF before, but only when using studio flashes, and I didn't go by the image on the LCD panel. I used the histogram.

Bingo!

[David A. Goldfarb]

Are you remembering to compensate for bellows factor, filter factor, and reciprocity? You still need to do that whether you use a regular light meter, DSLR, or rules like "sunny 16." Forgetting any of them will cause underexposure.

[pdmoylan]

In my experience, DSLRs do not work well as light meters. Though you could calibrate, it is important to standarize on one lens and test it. You end up adding more calculations though in addition to bellows and other exposure factors.

I have tested this over many years and use a Nikon FM2N for metering instead. It works great. I use any one of 3 lenses on it with no adjustments one relative to the others. Of course I throw in some 35mm film from time to time as well.

Be forwarned that not all LF lenses are calibrated correctly either. THough this could be corrected, I have one old wide angle LF lens which requires 1/3 overexposre compared to it counterparts.


PDM

[Greg Miller]

Be sure to set your Canon metering mode to something other than evaluative metering - such as spot or center weighted. Evaluative is an intelligent metering system that does things other than just give a straight meter reading. Using spot or center weight metering modes will give you a reading much more similar to a traditional meter.

[Andrea Gazzoni]

thanks for all the answers


Are you remembering to compensate for bellows factor, filter factor, and reciprocity?

yes David, I was applying any compensation needed. The filters where on the dslr also.


Be sure to set your Canon metering mode to something other than evaluative metering - such as spot or center weighted.

Just checked here at home under artificial light Greg, but it seems the Canon camera is giving the same readings in each metering mode. Should I expect some difference in the field?


How do the histograms for the "metering" look, if you still have those?

same here, all the histograms are a bit on the left side, see attachments.
could such a deviaton in the histogram correspond to a 1 full stop underexposure?

some more details:
-all the films used have expiry dates between 2007 and 2011
-in the first few shots the DSLR was set to an exposure compensation of -2 / 3 stop, while in the last session no compensation has been applied, but the final shots were still underexposed by a full stop

[Greg Miller]

Just checked here at home under artificial light Greg, but it seems the Canon camera is giving the same readings in each metering mode. Should I expect some difference in the field?


same here, all the histograms are a bit on the left side, see attachments.
could such a deviaton in the histogram correspond to a 1 full stop underexposure?

some more details:
-all the films used have expiry dates between 2007 and 2011
-in the first few shots the DSLR was set to an exposure compensation of -2 / 3 stop, while in the last session no compensation has been applied, but the final shots were still underexposed by a full stop

Yes, depending on the scene the different metering modes may or may not meter the same.

Are those screen shots from your digital files or from scanned film? The 2nd and 3rd both show highlight clipping (especially the 3rd) and therefor should have received less exposure. Don't worry about where the hump is - it can vary by scene. What you care about is highlight clipping and shadow clipping. You have clipped highligs in #2 and #3 and therefore have lost highlight detail.

[Andrea Gazzoni]

screenshots are from the digital files, Greg. What I am missing here is how could my former point&shoot digi nail very similar exposures, but mostly how could the correspondent film shots be literally almost black...

[Simon Liddiard]

I've used a dSLR as a light meter for LF before, but only when using studio flashes, and I didn't go by the image on the LCD panel. I used the histogram.

Agreed! The histogram is the only way to go if you're going to use a digital camera as a device to measure your exposure.

Firstly, if you shoot raw then the image on the back of the digital camera is only a jpeg rendering of the actual data captured by the sensor, and is subject to the interpretive processing designed by the camera manufacturer. Secondly the backlit LCD screen - possibly even with adjustable brightness - might well throw your guestimation even wider of the mark.

If you shoot jpeg the the preview will be more accurate, perhaps bringing you closer to a true WYSIWYG scenario... even so I think the histogram is more accurate than using the image preview.

[Simon Liddiard]

screenshots are from the digital files, Greg. What I am missing here is how could my former point&shoot digi nail very similar exposures, but mostly how could the correspondent film shots be literally almost black...

If you were using your 5D in raw format, and your cheap P&S only shoots jpeg then that would almost certainly explain the discrepancy. Opening raw files in Lightroom 5 illustrates this perfectly - the first image to appear is the jpeg preview, then the raw data is rendered, often giving very different results

[Simon Liddiard]

Well a couple of things come to mind.

First of you are shooting expired film. This alone could cause various issues in exposure.

Second many film photographers don't actually shoot shoot film at the speed listed on the box. Form example I like to shoot most ISO 100 films at ISO 50. But because every film type is different testing is required to find out what ISO a certain film pro forms best at for you.

Andrea is clear in her post that she re-did the test with fresh and expired film, but I'm struggling to understand how down-rating the films ISO is relevant to this issue - please can you elaborate further?

[Andrea Gazzoni]

so the camera is displaying a much darker raw file in the lcd? this should lead to overexpose, isn't it?

p.s. Simon, I am a male with obvious beard :-)

[Greg Miller]

screenshots are from the digital files, Greg. What I am missing here is how could my former point&shoot digi nail very similar exposures, but mostly how could the correspondent film shots be literally almost black...

I think it could be a lot of things, which none of us can tell for sure without knowing more. 2 of the 3 screen shots are not exposed properly (in my opinion; others may disagree) so maybe we all have a different idea of proper exposure. And your idea of 1 or 2 stops underexposed might be different than my idea. 2 stops underexposure on Velvia is very significant and would yield an extremely dense transparency. The screen shots all show using most of the dynamic range of the DSLR, which is way more dynamic range than Velvia can handle. It is entirely possible that the Velvia exposure was proper for holding highlight detail, but the contrastiness of Velvia pushed the mid-tones into deep shadow. That's just a matter of knowing your film and how it's dynamic range will cause a scene to render. Based on the screen shot histograms (which appear to show about 8 stops of dynamic range), I don't think Velvia is the right choice for any of them. On a different note, If you were using a Nikon camera as a meter I would say underexpose intentionally based on the Nikon's meter reading because Nikons tend to "expose to the right" which is fine for digital but not necessarily for film. Especially Velvia, with its limited dynamic range. Also, when I used Velvia, I always rated it at a lower ISO because I found I always was slightly underexposed when using at its rated ISO.

But I have to wonder about how accurate your LF lens is. How old is it, has been CLA'd, have you ever tested for shutter speed accuracy. Its quite possible that the lens is off by 1 or 2 stops, and it was juts a coincidence that the P&S gave you good meter readings.

Bottom line is you should be able to use the DSLR anyway for metering. Just set it on spot metering mode and do some calibration testing. Shoot several LF sheets at exposures around the Canon's meter reading, and see which sheet looks to be exposed the best. Compare that exposure with the DSLR's reading and you know how to compensate going forward.

[Simon Liddiard]

so the camera is displaying a much darker raw file in the lcd? this should lead to overexpose, isn't it?

p.s. Simon, I am a male with obvious beard :-)

Dude I'm so sorry, I did wonder! I have a couple of male friends called Lyndsey and Loren, which everyone misspells Lauren

[Greg Miller]

Agreed! The histogram is the only way to go if you're going to use a digital camera as a device to measure your exposure.

Firstly, if you shoot raw then the image on the back of the digital camera is only a jpeg rendering of the actual data captured by the sensor, and is subject to the interpretive processing designed by the camera manufacturer. Secondly the backlit LCD screen - possibly even with adjustable brightness - might well throw your guestimation even wider of the mark.

If you shoot jpeg the the preview will be more accurate, perhaps bringing you closer to a true WYSIWYG scenario... even so I think the histogram is more accurate than using the image preview.

The histogram is based on the jpg that is rendered, not the RAW file. I set my DSLr's so that they use the picture mode with the least contrast. This helps render a jpg whose histogram will most closely match the content of the RAW file.

[Andrea Gazzoni]

Its quite possible that the lens is off by 1 or 2 stops, and it was juts a coincidence that the P&S gave you good meterings

shouldn't a slow shutter lead to overexposed sheets?

anyway, this is not a lens issue.
I have the same results with both a 90mm and a 210mm..

[Greg Miller]

shouldn't a slow shutter lead to overexposed sheets?

anyway, this is not a lens issue.
I have the same results with both a 90mm and a 210mm..

The lens could be slow or fast.

You can pick up two light meters of the same brand/model and get different readings. If it were me, I would just run a calibration test and get on with life. That's what I do with any meter of any type.

[Simon Liddiard]

so the camera is displaying a much darker raw file in the lcd? this should lead to overexpose, isn't it?

The other way round - the camera LCD is displaying a jpeg interpretation of the raw file. Generally I find my LCD displyas a brighter more contrasty image, which when opened in a raw converter turns into a flatter, slightly darker image

I keep referring back to this article: http://www.luminous-landscape.com/tutorials/understanding-series/u-raw-files.shtml

This is also helpful - http://forums.adobe.com/message/4698680 (a lot of the posts are chit-chat, but the linked pages are good)

Getting a little off-topic now, but if you want to modify the camera settings to give a more accurate preview then search for UniWB

http://www.malch.com/nikon/UniWB.html

http://www.luminous-landscape.com/forum/index.php?topic=63997.0

and finally, for your camera - http://www.luminous-landscape.com/forum/index.php?topic=59776.0

[Simon Liddiard]

The histogram is based on the jpg that is rendered, not the RAW file. I set my DSLr's so that they use the picture mode with the least contrast. This helps render a jpg whose histogram will most closely match the content of the RAW file.

Yeah I'm just doing this now! (D700 - owned for 3 years, don't know why I haven't done it yet!)

[Greg Miller]

The other way round - the camera LCD is displaying a jpeg interpretation of the raw file. Generally I find my LCD displyas a brighter more contrasty image, which when opened in a raw converter turns into a flatter, slightly darker image

I keep referring back to this article: http://www.luminous-landscape.com/tutorials/understanding-series/u-raw-files.shtml

This is also helpful - http://forums.adobe.com/message/4698680 (a lot of the posts are chit-chat, but the linked pages are good)

Getting a little off-topic now, but if you want to modify the camera settings to give a more accurate preview then search for UniWB

http://www.malch.com/nikon/UniWB.html

http://www.luminous-landscape.com/forum/index.php?topic=63997.0

and finally, for your camera - http://www.luminous-landscape.com/forum/index.php?topic=59776.0

No. The jpg conversion is only going to compress the shadows and highlights. But will not make mid-tomes darker or brighter. It will only make the scene more contrasty (but not brighter or darker).

[Simon Liddiard]

No. The jpg conversion is only going to compress the shadows and highlights. But will not make mid-tomes darker or brighter. It will only make the scene more contrasty (but not brighter or darker).

You are probably correct. I think the slight alteration of the colour might lead me to perceive a darkening. The contrast is certainly altered.

[Greg Miller]

You are probably correct. I think the slight alteration of the colour might lead me to perceive a darkening. The contrast is certainly altered.

It's definitely correct. But it is irrelevant for this conversation anyway.

For most people shooting Velvia, the main concern is not blowing out highlight detail. Assuming 5 stops of exposure latitude, people generally will spot meter the highlight, then expose 1.5 to 2 stops stops under that. This keeps the highlights just below the point where they will blow out. And the mid-tones and shadows fall where they may. So Andrea needs to understand how to meter the highlights (this is where the spot meter mode comes in handy) with his DSLR, and then translate that to a proper exposure with his LF film (calibration testing).

[Simon Liddiard]

It's definitely correct. But it is irrelevant for this conversation anyway.

True. Just for clarity my comment about you being probably correct was only because I didn't have my camera to hand to verify myself, not because I doubted your information!

I found this article on calibrating a meter to a digital camera - http://www.frankdoorhof.com/site/2011/08/calibrating-the-light-meter-some-quick-notes/

Is that pointing in the right direction?

[Andrea Gazzoni]

The screen shots all show using most of the dynamic range of the DSLR, which is way more dynamic range than Velvia can handle. It is entirely possible that the Velvia exposure was proper for holding highlight detail, but the contrastiness of Velvia pushed the mid-tones into deep shadow


...understand how to meter the highlights (this is where the spot meter mode comes in handy) with his DSLR, and then translate that to a proper exposure with his LF film (calibration testing)

I'm not sure this is a matter of dynamic range, Greg.
I've often shot the same type of scene, always in low light, with almost only midtones. In the past I was always using Velvia 100 and I did not have these problems.
In my limited knowledge, scenes like the one attached here below are not so challenging for Velvia, none the less the film shot came out almost black.
It seems more likely that it is an improper use of the dslr on my part, combined with a minimum loss of speed of the film.
I am going to do some more tests, most of all I will have my Pentax spotmeter calibrated.
thank you all for your advice

[Simon Liddiard]

It seems more likely that it is an improper use of the dslr on my part, combined with a minimum loss of speed of the film.
I am going to do some more tests, most of all I will have my Pentax spotmeter calibrated.
thank you all for your advice

Keep us posted man, good luck

[Greg Miller]

I'm not sure this is a matter of dynamic range, Greg.
I've often shot the same type of scene, always in low light, with almost only midtones. In the past I was always using Velvia 100 and I did not have these problems.
In my limited knowledge, scenes like the one attached here below are not so challenging for Velvia, none the less the film shot came out almost black.
It seems more likely that it is an improper use of the dslr on my part, combined with a minimum loss of speed of the film.
I am going to do some more tests, most of all I will have my Pentax spotmeter calibrated.
thank you all for your advice

I'm just commenting based on the histograms that you posted. I may be wrong, but I believe the 5D II has about 8 or more stops of usable dynamic range. Velvia has 5 stops. The histograms show information from the far left (deep shadows) to the far right with some clipping (its possible that you increased contrast in the RAW conversion or post processing but I'm assuming these are straight out of the camera). That would mean that there is significantly more dynamic range in those specific scenes than the 5 stops of exposure latitude that Velvia can capture. So if you use Velvia (or pretty much any other transparency film) with these specific scenes, you have to make a compromising decision. Protect the highlights which will cause the mid-tones and shadows to be rendered darker than when seen with the human eye (and which it sounds like actually happened). Or expose the mid-tones so that they appear normal brightness, but allow the highlights to be blown out.

[Ed Bray]

I'm a little surprised that no one has mentioned (I didn't check all the links in posts) that DSLRs are calibrated to give a 12% grey whilst a typical meter is calibrated to give 18% grey.

[Simon Liddiard]

This is all useful information!

[Kirk Gittings]

I'm a little surprised that no one has mentioned (I didn't check all the links in posts) that DSLRs are calibrated to give a 12% grey whilst a typical meter is calibrated to give 18% grey.

Not so important if you use the histogram and pay close attention to the highlight and shadow renderings plus take into account the dynamic range of your film vs. the DSLR rather than paying attention to the midtones.

[paulr]

I love my dslr, but really wish the metering system were designed for people who knew what they were doing. as it is, the histograms only reflect the currently selected jpeg processing. There is no way to know the only thing that really matters, which is if any of the color channels have clipped in the raw file.

Some clever people have figured out hacks (like UniWB) that trick the camera into doing this, but then you completely sacrifice the usefulness of image reviews on the back screen. In order to get useful histograms you can't even see the pictures you just took.

How hard would it be to offer a raw histogram feature? I realize there are some complications, since nothing actually clips on the shadow end ... but you could pick a standard based on some level of average s/n ratio, and it would be so useful.

A "light meter mode" would also be useful. Not to lots of people, but this would just be a software item too. No actual cost to implement.

[paulr]

I'm a little surprised that no one has mentioned (I didn't check all the links in posts) that DSLRs are calibrated to give a 12% grey whilst a typical meter is calibrated to give 18% grey.

Is this true? New to me. Where can I read about the thinking behind this?

[Ed Bray]

Is this true? New to me. Where can I read about the thinking behind this?

Without being flippant, google it. There are loads of references to the fact that both Canon and Nikon calibrate their DSLR meters to 12% grey.

Here's one (http://www.bythom.com/graycards.htm)

There are a lot more.

[paulr]

That's interesting. According to the Thom Hogan post, it sounds like camera and meter manufacturers have been using the ANSI standard nearly forever, and so the 18% gray card has been off since before digital cameras showed up.

[thrice]

Also, if you're using longer focal lengths make sure you calculate for bellows extension.
http://www.largeformatphotography.info/bellows-factor.html

[Nathan Potter]

It doesn't matter what the DSLR is calibrated to, or if it is calibrated at all. If you want perfect film exposures you need to use the film to calibrate the DSLR meter. The simplest way I use is to attach a logD 3.0 step tablet to the LF film then use the DSLR to meter an 18% grey card. Then over expose the LF film by about 5 stops so the grey card exposure falls at about log D 1.5 on the log D 3.0 step tablet. Use your normal development for the film/DSLR you have chosen to calibrate. The image of the step tablet on the film will show exactly where zone II or zone VIII falls if that is your choice for shadow and highlight texture values. There are other procedures that amount to the same thing and as I said previously check a number of publications describing such techniques.

Nate Potter, Austin TX., Steuben ME.

[Simon Liddiard]

It doesn't matter what the DSLR is calibrated to, or if it is calibrated at all. If you want perfect film exposures you need to use the film to calibrate the DSLR meter. The simplest way I use is to attach a logD 3.0 step tablet to the LF film then use the DSLR to meter an 18% grey card. Then over expose the LF film by about 5 stops so the grey card exposure falls at about log D 1.5 on the log D 3.0 step tablet. Use your normal development for the film/DSLR you have chosen to calibrate. The image of the step tablet on the film will show exactly where zone II or zone VIII falls if that is your choice for shadow and highlight texture values. There are other procedures that amount to the same thing and as I said previously check a number of publications describing such techniques.

Nate Potter, Austin TX., Steuben ME.

I had to google this... now I'm facing a challenging weekend

[Ed Bray]

It doesn't matter what the DSLR is calibrated to, or if it is calibrated at all. If you want perfect film exposures you need to use the film to calibrate the DSLR meter. The simplest way I use is to attach a logD 3.0 step tablet to the LF film then use the DSLR to meter an 18% grey card. Then over expose the LF film by about 5 stops so the grey card exposure falls at about log D 1.5 on the log D 3.0 step tablet. Use your normal development for the film/DSLR you have chosen to calibrate. The image of the step tablet on the film will show exactly where zone II or zone VIII falls if that is your choice for shadow and highlight texture values. There are other procedures that amount to the same thing and as I said previously check a number of publications describing such techniques.

Nate Potter, Austin TX., Steuben ME.

Hi Nate,

Ideally we would all calibrate our meters/lenses/development regime/film stock to ensure we can get repeatable accurate results that work for us.

Unfortunately when people buy a lightmeter they often 'ass u me' that the lightmeter is calibrated at the factory to give an 18% grey (Zone 5) when they are taking a reflected reading of any particular plain tone and base their exposure on that without any further testing. If a DSLR meter is used to take the light level reading (when calibrated to approx. 12% grey) then it is typical that the reading expected to be Zone 5 will a Zone 6 and therefore lead to approx -1 stop less of exposure given. If the film/development/lens and DSLR had been previously used to obtain a working EI for that user then the issue is moot as the difference would have been factored out during the testing regime.

If any photographer changes their meter or method of metering then any previous testing carried out will not be accurate although with B&W or Colour Print film there may be sufficient latitude for an acceptable result, whilst we are all aware of how little latitude Transparency film has and the difference could be sufficient to give unacceptable results.

[Nathan Potter]

Ed, yes I agree with what you have said. I did not know that about the 12% vs 18% grey calibration. I never used a DSLR until about a year ago and quickly discovered that it over exposed my images by about 2/3 of a stop.

If the OP has calibrated his film previously using a different meter he still may be in trouble after compensating for the 12% differential if the two meters have not been calibrated with each other. Of course it depends upon how fussy one is about accuracy of exposure.

Nate Potter, Austin TX., Steuben ME.

[Greg Miller]

Without being flippant, google it. There are loads of references to the fact that both Canon and Nikon calibrate their DSLR meters to 12% grey.

Here's one (http://www.bythom.com/graycards.htm)

There are a lot more.

This isn't as big a deal as may seem. The % is the reflectance of the card, not the luminosity of the gray. Somebody decided the world averages to 18% reflectance. But so many specific scense are drastically different. We've been living with this long before digital.

[Andrea Gazzoni]

some quick test shots with the 5D MKII today. a sunny november morning, with some thin clouds.
camera set in aperture priority mode, iso 100.
if I compare these EV readings side by side to any standard chart (for example http://en.wikipedia.org/wiki/Exposure_value),
it seems to me that the dslr readings are off by 1.3 to 2 full stops.
in other words it is making me underexpose the film up to 2 stops, if I copy these readings to the LF camera.
I'd better not shoot Velvia at 2 seconds instead of say 6-8 seconds (12 with reciprocity?)...
does this make any sense? how would you meter similar scenes if no lightmeter was available?


https://dl.dropboxusercontent.com/u/94184552/EV%2011.JPG

https://dl.dropboxusercontent.com/u/94184552/EV%2010-3.JPG

https://dl.dropboxusercontent.com/u/94184552/EV%2012-6.JPG

[Greg Miller]

This may sound harsh, but I'm thinking you have ignored the advice already offered here, and gone off on another tangent. Calibrate your camera's meter to your film. Learn to base your exposure for (the limited dynamic range of Velvia) by exposing for the highlights.

And don't expose Velvia if you don't have a light meter (unless you are skilled enough to determine the exposure within 1/3 stop without one).

[Nathan Potter]

Velvia, particularly, has a really limited dynamic range so one must be pretty much dead nuts on exposure placement for where you want a particular level of detail. Then you'll have to let the shadows or highlights clip (DSLR jargon) or blown (analogue jargon). That's why I tend to use Velvia in compact lighting situations (cloudy days, for example).

Recently I've come to using a LF version of HDR where I'll take 2 or 3 identical frames but say at -2, 0, and +2 stop brackets. Then I'll use an HDR software package to combine at post scanning. This can effectively double the dynamic range of the Velvia. I have gone -3, 0 and +3 brackets to yield a nominally 10 EV dynamic range, providing the shadow noise can be controlled during tone mapping.

As Greg has reiterated, it is really necessary to do an accurate calibration of film to meter in order to obtain predictable results both for accurate placement of the exposure and a pre visualization of the scene brightness range to film capability.

Part of your difficulty may be in using a grey card for exposure determination then trying to apply that reading to a scene of large dynamic range.
I might suggest the quick experiment of placing a large 18% grey card in an actual scene. Then do a standard development and check the density of the grey card in the resulting film.

Nate Potter, Austin TX., Steuben ME.

[Light Guru]

This may sound harsh, but I'm thinking you have ignored the advice already offered here, and gone off on another tangent. Calibrate your camera's meter to your film. Learn to base your exposure for (the limited dynamic range of Velvia) by exposing for the highlights.

And don't expose Velvia if you don't have a light meter (unless you are skilled enough to determine the exposure within 1/3 stop without one).

Bingo! All those new "tests" don't mean a whole lot if you don't have a film example to compare them to.

Take a exposure on the film you are calibrating your camera meter to the. Take a series of bracketed exposures with your DSLR Compare the developed film and the bracketed exposures.

If you determine that your dslr is say over exposing my 2 stopes then adjust the ISO rating you shoot your film at by 2 stopes. This will give you consistent exposures between your dslr when set at this adjusted ISO and your film.

Get it?

[David Lobato]

It sure seems to me that a DSLR reading, typically from a matrix meter, and adjusted with right or left movement of the histogram, completely loses the reference baseline of 18% gray - which is vital for film exposures. Any cheap reflected light meter will provide the proper exposure and will quickly pay for itself in saved film. Many times a perceived shortcut turns out to be a long winding path to confusion.

[Andrea Gazzoni]

Ok, forget about film, lightmeter, LF camera for a minute. you just have a dslr. ok it does anything, but...
it is correct to expect that the readings of the dslr differ by 2 stops from the norm?
in other words, do these charts still mean anything in the digital world?

I know it just takes a roll of film to get the point of calibrating my film, will do it when time permits.
It may sound stupid to someone here, but I am trying to understand the digital toy a bit better.
I'll grab some friend's dslr too and check how their readings compare.

[Light Guru]

Ok, forget about film, lightmeter, LF camera for a minute. you just have a dslr. ok it does anything, but...
it is correct to expect that the readings of the dslr differ by 2 stops from the norm?
in other words, do these charts still mean anything in the digital world?

I know it just takes a roll of film to get the point of calibrating my film, will do it when time permits.
It may sound stupid to someone here, but I am trying to understand the digital toy a bit better.
I'll grab some friend's dslr too and check how their readings compare.

I dont think your DSLR is 2 stops off. I think the whole problem is that you failed to understand before originally shooting the film that the ISO in the box of film is just a recommended starting point. Testing and adjusting is ALWAYS needed when starting with a new type of film.

[Andrea Gazzoni]

I dont think your DSLR is 2 stops off. I think the whole problem is that you failed to understand before originally shooting the film that the ISO in the box of film is just a recommended starting point. Testing and adjusting is ALWAYS needed when starting with a new type of film.

who said it is new for me?
I am shooting this film at the advertised ISO since almost 4 years, never had such issues.

[paulr]

If jpegs from your dslr look ok, then the meter isn't off by two stops. It's probably off by a half stop, by design ... see the DXO test chart I posted for your camera.
If you want to know for sure, compare with a trusted light meter. Otherwise you'll just keep going around in circles.

[Greg Miller]

Ok, forget about film, lightmeter, LF camera for a minute. you just have a dslr. ok it does anything, but...
it is correct to expect that the readings of the dslr differ by 2 stops from the norm?
in other words, do these charts still mean anything in the digital world?

I know it just takes a roll of film to get the point of calibrating my film, will do it when time permits.
It may sound stupid to someone here, but I am trying to understand the digital toy a bit better.
I'll grab some friend's dslr too and check how their readings compare.

You have not told us what metering mode your dslr is set on. If evaluative/matrix then all bets are off because the meter will try to adjust the exposure based on what type of scene it thinks you are shooting. If you are going to do this exercise, then you MUST switch to spot or center weighted. But even then I would not put much stock in what you are doing. Look through the viewfinder and move the camera just a little bit and watch what happens to the meter reading. You're likely to see pretty big changes in the meter reading.

[David Lobato]

Andrea, your 3 photos above all have some amount of bright areas and the Canon Evaluative meter will add exposure to compensate, which brightens the dark areas. That is why all the camera meter EV values are all less than the chart values. A hand held meter averaging all of each scene would probably match the chart EV levels. If it is angled down toward the darker values of the trees and the ground, it would show lower EV values and closer to the Canon's EV values. Light metering is an art and takes some experience to understand. Continue to ask questions as you learn to judge light.

[richardman]

7 pages of??? May be your view camera lens are drastically different from the Canon lens? May be Canon lies about their ISO (it happens more often than you'd think)?

Anyway, just buy a used meter for $40 and not worry about wasting film. I just bought a Gossen digisix ($150) but I'm sure there must be billions of used meters out there needing love.

[Light Guru]

who said it is new for me?
I am shooting this film at the advertised ISO since almost 4 years, never had such issues.

Now that is important information that should have been included in your original post. Now how you been using the same dslr to meter this film for the last 4 years?

[Light Guru]

just buy a used meter for $40 and not worry about wasting film.

Even when guys a light mete you need to do tests to ensure that the exposure reading you get from the meter will give you a good exposure not he film.

[richardman]

Even when guys a light mete you need to do tests to ensure that the exposure reading you get from the meter will give you a good exposure not he film.

Oh I agree, but it's one less variable. A lightmeter is a simple dedicated tool. One glance and you know what it's doing, and not having to double check the dSLR to make sure it's using the right metering mode, the right ISO etc. The digisix can also go as low as -9EV, which comes in pretty convenient for low light work.

[Andrea Gazzoni]

Now that is important information that should have been included in your original post. Now how you been using the same dslr to meter this film for the last 4 years?

Zac, in the last four years I've been using a compact digital camera plus the spotmeter. The readings were so consistent even in questionable light, that at some point 2 years ago I started living the spotmeter in the backpack.


You have not told us what metering mode your dslr is set on... If you are going to do this exercise, then you MUST switch to spot or center weighted.

the 3 shots above were in center weighted mode

[Light Guru]

Zac, in the last four years I've been using a compact digital camera plus the spotmeter. The readings were so consistent even in questionable light, that at some point 2 years ago I started living the spotmeter in the backpack.

And now we find out you have a spot meter all along.

Why have you not compared the readings from your old compact camera and the light meter with that of your new 5dmk2.

If I had been getting fine exposures with one method of metering for years and wanted to switch meters I most settings would compare the readings from my old meter with my new one before going out to shoot.

[Andrea Gazzoni]

because both my meter and my old compact camera are not working anymore...