Can anyone give me the bellows factor for 4 and 6 feet of bellows length.. thx
Can anyone give me the bellows factor for 4 and 6 feet of bellows length.. thx
Depends on the focal length of the lens used.
required exposure time/metered exposure time = (image distance/focal length)^2
405mm..lens
Maybe you could just put a 2-inch object in the set and read the factor off the Kodak BF strip on the groundglass. I mentioned elswhere that I keep a copy of the strip rolled up un a 2" tube.
Lets say If I used a probe and an 18% gray card would that give me basicly the same reading as an incident reading might ?
Steve,
If by probe, you mean the Sinar through the lens meter doohickey, then that automatically compensates for bellows factor (because it is through-the-lens.)
That depends on whether there is enough light to activate the sensor.
As you can see, the calculation really isn't that difficult :
Bellows length (squared) divided by the focal length (squared) gives you the exposure factor.
So, e.g. for & 210mm lens and a bellows of 420mm, the exposure factor is 4x, thus use 2 stops.
It's much easier to just measure the aperture diameter through the front element, measure the bellows extension, and divide the latter by the former to get the actual f/stop. Much simpler than squaring one thing, then squaring another, then dividing, then translating the factor.
It keeps you in touch with the simplicity of the focal length/aperture relationship. I never understood why so many large format photographers prefer the longer formula...
"I love my Verito lens, but I always have to sharpen everything in Photoshop..."
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