I want to do some close up work with LF, but how do I know how to compensate my exposure for light fall off from the extended bellows? and I have an old Schnieder 150mm f/4.5, does the image circle decrease when focused so close?
Thanks
Chad
I want to do some close up work with LF, but how do I know how to compensate my exposure for light fall off from the extended bellows? and I have an old Schnieder 150mm f/4.5, does the image circle decrease when focused so close?
Thanks
Chad
hello,
For a 150 mm lense at 1:1 , it means extensionx bellows of 300 mm
With ligtmeter , you read f11 for example, it means 2x more aperture on the lense,
idem est f5.6
Bye
Here's what i've got: $10.99 and never fails
http://www.calumetphoto.com/ctl?ac.u...7;20calculator
http://www.amazon.com/Stanley-33-425...0497226&sr=1-2
That's the tool I like...
Chad - just square (multiply by itself) the factor of (measured lens-to-film distance) divided by (measured lens-to-film distance at infinity). So - for a doubling of focal length - you have 4x the indicated exposure - 2 stops, etc...
I figure it out and print a scale that I stick to the lensboard.
-Chris
I bought the same Calumet thing for $10.99 before I found this:
http://www.southbristolviews.com/pic...ic/SBVCALC.pdf
Free is cheaper than $10.99. There is another one on the web, but I can't seem to locate it.
There's quite a good write up here:
http://www.largeformatphotography.in...ws-factor.html
And the "QuickDisc" is here:
http://www.salzgeber.at/disc/index.html
Jonathan
The method described by John Cook (who was one of the wiser and more entertaining contributors to this site) in Johnathan Perkins's link works just fine.
I have the Calumet target, but I'm too lazy to use it, and often using a target ranges from inconvenient to impractical. If you have access to Jack Dykinga's book, Large Format Nature Photography, there is a photo on p. 90 showing the use of the Calumet target to photograph part of a cactus. Unless Dykinga is shooting straight down, something is holding the target in place, failing which he could not have used it. Perhaps because he found the target inconvenient (he doesn't elaborate), he then decided to use the target to test various distance scenarios in his kitchen, from which he made labels that he affixed, for each of two lenses, every couple of centimeters along the rail of his camera (p. 92). He guesstimates between labels. It's one solution.
Over the travel distance of your 150mm lens from 15cm/6" to 30cm/12", which gets you to 1:1, we are talking about a total of two stops. Consider the vagaries, technical and aesthetic, of exposure, and then decide just how much time you want to spend worrying about this.
This may sound a bit heretical, but when I do closeups, I shoot a couple of Polaroid test shots (for composition reasons as well as exposure), and often bracket as well, so I don't get too worked up about calculating bellows compensation to 1/3 of a stop
As Mr. Dewdney says, a tape measure comes in handy.
Last edited by r.e.; 23-Sep-2007 at 12:10.
No one else had said it yet: To answer one of your questions--As you extend bellows from infinity to 1:1, the image circle, which is a "cone" of fixed angle (e..g, 65, 70, 72 degrees, etc.) becomes LARGER at the film plane.
Peter
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