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I have a full frame A7R2 digital camera. Can I use it's integrated metering to find the correct settings to use on my medium format film camera? Do I have to convert anything, because of the different medium (6x4.5 120 film vs 35mm digital sensor)?

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  • \$\begingroup\$ I find it is easier to use a spot meter because I can take multiple readings in several zones and each reading is a single light value/EV_100 rather than a combination of ISO, aperture and shutter. Then again, part of what I like about shooting film when I shoot film is not using a DSLR and taking my time. \$\endgroup\$
    – user50888
    Commented Sep 22, 2017 at 2:10
  • \$\begingroup\$ I agree, but they are so expensive and shooting film is the exception for me. Not really worth the investment for me. \$\endgroup\$
    – Andreas Hartmann
    Commented Sep 22, 2017 at 7:04
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    \$\begingroup\$ Shooting film is the exception for me as well. I paid under $100US for a used analog spotmeter. I use it sometimes for the DSLR as well. Particularly under atypical lighting conditions. Having a habit/process makes shooting film less worrisome. \$\endgroup\$
    – user50888
    Commented Sep 22, 2017 at 13:16
  • \$\begingroup\$ May I ask which one you are using? I haven't been able to find one for that little money. \$\endgroup\$
    – Andreas Hartmann
    Commented Sep 22, 2017 at 15:00
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    \$\begingroup\$ A Rokunor Analog. The seller said was made by Soligor. It looks pretty similar to the meters Soligor made and the seller has a 100% Ebay reputation (many photography sales) and the internet suggests Soligor made 'white label' spotmeters (including some for Adorama). The key features for me: takes ordinary batteries (a 9v in this case) and was known to be working. I also prefer the dial style 'calculator' because I can see many options at a glance rather than pressing tiny buttons and depending on 20+ year old electronics and switches. \$\endgroup\$
    – user50888
    Commented Sep 22, 2017 at 15:35

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Can I use my full frame digital camera to set up the exposure for my medium format film camera?

Yes, you can use a digital camera to take test shots in much the same way pros used Polaroid backs for many years. Just keep in mind that both film and digital have some leeway with regard to ISO. Many digital cameras can be 1/2 stop or more less sensitive than they claim for a particular ISO. One of the things DxO Mark tests is actual sensitivity for each full ISO stop. Here's a link for the Nikon D610 and Canon 6D (You'll need to click Measurements-->ISO Sensitivity to see the comparison).

Different films also vary slightly from the exact ISO they are rated at. You might run into a case where both the film and digital vary by the same amount in the same direction and so they are both almost equally sensitive or you might find a combination where the film is more sensitive and the digital camera is less sensitive and wind up with differences that add to one another.

Do I have to convert anything, because of the different medium (6x4.5 120 film vs 35mm digital sensor)?

No. Nothing must be converted due to the different format sizes.

However, if contemplating exposures for film longer than about 1 second the Schwarzschild effect, sometimes referred to as reciprocity failure, must be taken into account. This can very significantly impact exposure times, and it varies by the specific film in question. The manufacturer of your film should be able to provide information regarding how much compensation is needed for longer exposures.

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  • \$\begingroup\$ Thanks, especially for the hint about the Schwarzschild effect, I wasn't aware of that! I am indeed aiming for long exposures. Great answer! \$\endgroup\$
    – Andreas Hartmann
    Commented Sep 21, 2017 at 12:45
  • \$\begingroup\$ I'll accept it as soon as it's unlocked. \$\endgroup\$
    – Andreas Hartmann
    Commented Sep 21, 2017 at 12:46
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    \$\begingroup\$ See also this answer to Why are these film photos brighter than digital photos taken at the same time with the same settings? for some of the more subtle differences between the way film and digital each handle highlights and shadows. \$\endgroup\$
    – Michael C
    Commented Sep 21, 2017 at 12:56
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    \$\begingroup\$ I prefer the term reciprocity failure. Karl Schwarzschild, an astronomer, devised a formula to predict the needed compensation for extended exposure time. Exposure to light weakens the silver-haloid bond. This is the trigger that causes the developer to reduce the crystal. Its two parts are liberated to metallic silver and a water soluble halogen. If the exposure is lengthy (several seconds or longer), some healing occurs --- now more photon hits are required to render the crystal developable. \$\endgroup\$
    – Alan Marcus
    Commented Sep 21, 2017 at 14:54
  • \$\begingroup\$ @AlanMarcus Both terms are included in the answer. \$\endgroup\$
    – Michael C
    Commented Sep 22, 2017 at 1:29
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Yes, you can do this provided you set your digital camera's ISO equal to the film speed you're using. Aperture and shutter speed values for exposure purposes translate between film and digital, and film formats and sensor sizes. The only time you would have to "adjust" is with large format film (like 8x10) where bellows extension comes into play.

Of course you should always test before doing any critical work.

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