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Old 3rd May 2020, 01:25 PM
Terry S Terry S is offline
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Default Calculating exposure with 5 X 4 bellows extention

Hi all,

I'll immediately put my hand up and say that I have only had one (failed) experience of using a 5 x 4 camera with long bellows, whilst at Uni recently. It just wasn't something that was given any time to.

Anyway, I have a well made, home made (but not by me), wooden 5 x 4 camera with short bellows and lens / shutter, that I would like to have a go with, during this lock down.

I was told (very quickly) a very basic exposure formula for when extending the bellows by one of the lecturers, but I can't recall it. It was something like, + 1 f - stop for every inch (or two?) of the bellows.

Is this about right? Or is there another (most important here!) VERY simple formula, to get me up and running?

Many thanks,

Terry S
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Old 3rd May 2020, 04:34 PM
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MartyNL MartyNL is offline
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Terry, my understanding of the VERY basic bellows extension calculation is that you add +1 stop for every additional 50% of the lens focal length that you're using. A small tape measure is useful.

So lets say a 210mm lens focussed at 315mm is +1 full stop of extra exposure. Likewise the same lens at 260 will be +1/2 stop extra exposure.

Better still, I can highly recommend the bellows factor app by RDQ smart productivity tools fantastic app free with no ads etc.
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Old 3rd May 2020, 05:59 PM
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B&W Neil B&W Neil is offline
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There are plenty of good free APs that cover bellows extesion (and much more) available now - as long yoiu have a phone that is. I chucked my charts / tables years ago. Have a look at the one Marty has suggested.

Neil.
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Old 3rd May 2020, 06:24 PM
Lostlabours Lostlabours is offline
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Many years ago I marked the trackbed of my Wistra 45DX with the exposure factors in thirds of a stop for a 150mm lens, over 40 years later they are sill there.

Ut's worth doing something similar.

Ian
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Old 3rd May 2020, 09:48 PM
JOReynolds JOReynolds is offline
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Sinar used to sell a clutch-pen for Chinagraph 'leads' that was intended to calculate the increase. It was included in the camera-lens-darkslides package when I bought a 5 x 4" Norma, new, in about 1966. I sold it when my first son was born but I still have the pen, hardly used.
The cap of the clutch-pen is placed in the subject area and the length of its ground-glass image is compared with the scale (in f-stops) on the body of the pen. I used it on studio food shots.
One day I hope to acquire another Sinar but I don't have a 5x4" enlarger (or room for one in my cramped darkroom).
I still have a few sheets of 5 x 4" non-interleaved Ektacolor Internegative Film 6110, dated May 1972. I'm afraid they have been out of the freezer for several years. Or is it decades?
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Old 4th May 2020, 07:08 AM
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skellum skellum is offline
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http://www.salzgeber.at/disc/

Hi Terry,
This page gives the formula for calculating bellows compensation.

It also has a download for the 'quickdisc'.
The first part is a disc you include in the composition.
The second part is a ruler with which you measure the apparent size of the disc directly on the ground glass of your camera.

The ruler then lets you read off the degree of compensation needed.
I've had one of these laminated in a pocket of my camera bag for years.
Very quick and easy.
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Old 4th May 2020, 11:11 AM
Terry S Terry S is offline
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Thanks for all the suggestions everyone.

I'll work my way through the suggestions later and see which one I find easiest to use.

Terry S
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