Are there any light meters that take into account bellows extension?
Are there any light meters that take into account bellows extension?
Sort of. The Sinar metering backs meter at the film plane, with appropriate accessories, so that takes everything into account, including bellows, filters, etc. Lacking that, if you calculate the bellows factor, you can enter the compensation factor into your meter (some meters) and read the meter directly. Is this what you have in mind?
after doing closeup work for a while with a particular lens, you'll know how much to adjust for via the ISO dial, w/o measuring the bellows etc.
Not to my knowledge but the Expodev application for BTZS as used on the Palm or now on the iPhone accounts for Bellows filters and reciprocity. It only workes though with data test files for the BTZS [system].
Many experienced workers use a simple method of 25% bellows extension = 1/2 stop exposure increase. Eg a 12" lens at 15" add 1/2 stop of exposure.
That's mathematically correct and accurate.Originally Posted by Steve Nicholls
Mark the position of the front standard when the camera is focused at infinity,
then measure its position when focused on the subject as desired.
The difference between these two values equals the bellows extension.
For a life-size image (1:1 ratio) the extension should equal the lens focal length.
The extension divided by the lens focal length is the extension factor.
The method given is accurate for any lens.
Making a single measurement in the close-focus position and assuming the lens focal length
as a starting point can introduce a significant error with some lenses.
To answer the OP's original question...
Any throught-the-lens (TTL) metering system will automatically compensate for bellows
and for any lens attachments or modifiers.
- Leigh
If you believe you can, or you believe you can't... you're right.
Get a Quick Disc and you can use any meter.
Kent in SD
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Jay,
Yeah, entering the compensation factor into the meter is what I had in mind. I can of course just do the math myself but I'm considering buying a new light meter and was wondering if there were any that had this feature. Any specific recommendations?
Nothing beats informed experience and a few bad negatives. Do the math for a while—eventually you'll be able to make the correction without thinking much.
Seriously: Pre-figure the correction for your favorite lens(es). For a 150mm lens, each inch of extension beyond six inches requires 1/3 stop additional exposure. For a 210mm lens the correction for each inch of extension beyond 8 inches is 1/4 stop additional exposure.
Figure it out once and write it down. Use a short piece of cloth measuring tape to check the distance from GG to the lens board (OK the primary node) and check your pre-figured table. After a while this will become part of your process.
Drew Bedo
www.quietlightphoto.com
http://www.artsyhome.com/author/drew-bedo
There are only three types of mounting flanges; too big, too small and wrong thread!
1:1 is 2 stops.
It's easy to remember, and you can interpolate tolerably well for less/more magnification.
Science is what we understand well enough to explain to a computer. Art is everything else we do.
--A=B by Petkovšek et. al.
I think most meters can be made to function this way, by one method or another. Altering the ISO setting might be the most universally available method. For instance, if your bellows extension is 50%, and you're using ISO 400 film (and rate that film at EI400), you can simply set your meter to ISO 200 and read it directly. Different meters have different kinds of exposure compensation mechanisms, but they all accomplish the same thing as adjusting the ISO on the meter. I hope this helps.
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