exposure issues using a DSLR as a lightmeter

[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.