So I just bought a Mamiya RB67 Pro (not Pro S or SD) and I have heard you can meter with a DSLR. I have a Nikon D7100 and I thought, "Why buy an expensive light meter when I can just use my DSLR?"

I am aware that you have to do some math. I am going to shoot with TRI-X 400. I was just wondering if someone could give me a formula of some type so I can use my Nikon D7100 to meter for my Medium format RB67.


2 Answers 2


If you can set your D7100 to the same ISO and aperture as your RB67 while using a focal length that provides the same field of view as the lens attached to the Mamiya you don't really need to do any math at all. Just dial the indicated shutter speed from the Nikon when the meter is centered in Manual exposure mode into the Mamiya. If you elect to spot meter you don't even have to worry about the focal length/FoV.

Do note that many digital cameras tend to "cheat" a little in terms of actual ISO sensitivity versus the set ISO. Before you shoot too much film you should probably run a test roll to be sure it's in the ballpark. You'll probably find that you need to set the D7100 to ISO 500 or even 640 to simulate Tri-X when shot at ISO 400.


You could also just buy a light meter. That's what we used before DSLRs were created. They fit in a pocket, too.

  • 1
    \$\begingroup\$ yeah its just they are so expensive \$\endgroup\$ Sep 2, 2016 at 1:28
  • \$\begingroup\$ Not as expensive as a D7100 and lens. \$\endgroup\$
    – Michael C
    Sep 2, 2016 at 3:53
  • \$\begingroup\$ @lawson boucher, they really aren't expensive. B&H sells a good one, with flash metering, for $199. That's a whole lot easier and cheaper than carrrying around a second camera and lens. bhphotovideo.com/c/product/1219217-REG/… \$\endgroup\$
    – DocPixel
    Sep 3, 2016 at 17:28
  • \$\begingroup\$ i might look into the b&h one its just i have a dslr with a lens already so i figured i have the the mamiya and i have the d7100 so i wanted to shoot and not wait to get a meter, i will get a meter tho \$\endgroup\$ Sep 5, 2016 at 14:17

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