Bellows Compensation

Hi All,

I'm having some issues because math isn't my strong point. Im used to using a 4x5 with a 200mm lens. Wonderful setup in its simplicity for computing bellows compensation.

However I have a bellows unit for my DSLR now and am having trouble finding any sort of reliable information on the internet. Usually the "answer" is just use the internal TTL metering and it should compensate.

Sounds good to me but it isn't always feasible. So does anyone know of where to find reliable information regarding 35mm.

I have a full frame DSLR and am trying to use it with a 200mm f/2.8 lens on the bellows.

I have this feeling its going to be simple and make me feel stupid, but Ive been trying too hard I think at this point. I probably am over complicating it especially since I've done compensation with a 4x5 but I cant seem to get it figured out.

Thanks,

Max

Tags: 35mm, bellows, compensation

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Permalink Reply by nathan mccreery on January 25, 2012 at 3:24pm

Hey Max, Hope you didn't stop using the 4x5 permanently. Bellows draw compensation is relatively easy. It's funny, I used to carry a chart in my backpack but found that I was usually really close using an educated guess. Here's a simple formula.

I guess it's a bit of a mystery to me that the meter in your camera won't give you a compensated reading unless it is that the aperture contacts aren't operational. But in that case how are you stopping the lens down, and is there a reason to use bellows instead of a macro lens and extension tubes that would be set up to work with your metering system.

Formula: Divide the focal length of the lens into the total bellows extension, take away one, and that's the fraction of a stop, or number of stops, that you need to open the lens or extend the shutter speed by.
For example: 150mm lens with 240 mm bellows draw. 240 divided by 150 is 1.6, minus 1 leaves 0.6. Therefore; open up 0.6 stops (2/3rds stop is close enough).

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Permalink Reply by Max Kalkman on January 25, 2012 at 4:03pm

I love 4x5 and wont give it up or 2.25 either. I have a friend who is a painter and I like to tell people, "she never paints a whole painting using just 1 brush, and different formats and even film vs digital are just different brushes for me to use."

There aren't aperture contacts that function due to the bellows unit I'm using. It has some other perks though that make it worth my while to use this unit over the old Nikon ones. Does Nikon even make bellows units anymore?

Also I'm shooting some circuitry and crystals are involved which is creating a rather unique situation at least in my experience. I've shot jewelry before so I thought gemstones could be temperamental sometimes but this is turning out to be a whole different beast.

Anyways thanks for the formula. I just tried a test shot using the 200mm lens with 90mm bellows extension which using your formula gave me 2.2 - 1 = 1.2 so I lost just under 1 and 1/3 stop, am I correct?

I guess the reason I got confused was I used to use a slightly different equation and film size factored in. I think I'll just be sticking to your formula now. Thank you.