Bellows extension

[joefreeman]

I've found this method to be the easiest and fastest way:

1. measure the extension and square it.
2. divide 1's resulting number by the square of the focal length of the lens
3. divide your films iso by 2's resulting number
4. meter the scene with your new iso.

[rgacpa]

Originally Posted by Terry Bowyer

Is anyone out there able to give me an easy to understand explanation of this 'bellows extension compensation' that I have been hearing about. Just bought my first 4x5 camera (Zone VI) with a 210mm and 80mm lens. I haven't taken any photos yet, but like to be prepared for when I do.

Hi Terry,

I'm somewhat new at this too, but the easiest method I've heard described is that every 25% increase in your bellows extension from infinity focus = 50% increase in required exposure.

For example, you have an 8 inch lens (210mm), then your bellows extension for infinity focus is 8 inches. If you're focusing closer, you extend your bellows. So if you extend your bellows to 10 inches, you've increased your bellows extension by 25%. Increase your exposure by 1/2 stop.

This is born out by the more complicated formula (for me to do in my head) of bellows extension squared divided by focal length squared = exposure comensation.

Other methods are given in earlier posts to this thread or at:
http://www.largeformatphotography.in...ws-factor.html

Best,
Bob

[RJS]

If you are new to view cameras you really should purchase one of the excellent books available, either new or used. I have an older copy of Stroebel (sp) which I would be happy to part withfor a couple of dollars plus shipping. I believe Steve Simmons has a book out on the view camera, and there are doubtless others. The age of the book hardly matters as view cameras have changed hardly at all in the last 100? years. Stroebel, or one of the others will teach you all the insand outs plus bellows extension. I don't mean to diss what you reas here, but there is more to the view camera!

[Phillip P. Dimor]

I use a Quickdisc too. Very handy. You can have your local lab print it out for you and spray glue or gluestick it onto some cardboard or foam board.
Don't forget about reciprocity failure too, if you're doing macro work with long exposures..
Fun!

[Barrie B.]

Originally Posted by Terry Bowyer

Is anyone out there able to give me an easy to understand explanation of this 'bellows extension compensation' that I have been hearing about. Just bought my first 4x5 camera (Zone VI) with a 210mm and 80mm lens. I haven't taken any photos yet, but like to be prepared for when I do.

Greetings , Buy some Black and White film ,load up some double darks and take some images, you will enjoy the process. However shpould you decide to ' come in close' for some images I recommend you make one of these :-A quick Disc, invented by Philipp Salzeber,you can read off the exposure compensation at any time without having to do any maths. You can download one to print out on yor computer. :- http://www.salzgeber.at/disc/ Enjoy.
Barrie B. Melbourne Australia.

[Mateo]

this can be easy if you want it to be

if you got a 5.6 inch lens and you extend the bellows to 8 inches you need to add a stop
if you got a 5.6 inch lens and you extend the bellows to 11 inches you need to add 2 stops

if you got a 210mm lens and you extend 320mm you ain't gonna be far off if you add 1 stop
if you got a 210mm lens and you extend 450mm you ain't gonna be far off if you add 2 stops

see the pattern, forget about inverse square law this is quick and dirty and if you can be more accurate you have some super calibrated lenses and need to calm down

[jnanian]

Originally Posted by Mateo

this can be easy if you want it to be

if you got a 5.6 inch lens and you extend the bellows to 8 inches you need to add a stop
if you got a 5.6 inch lens and you extend the bellows to 11 inches you need to add 2 stops

if you got a 210mm lens and you extend 320mm you ain't gonna be far off if you add 1 stop
if you got a 210mm lens and you extend 450mm you ain't gonna be far off if you add 2 stops

see the pattern, forget about inverse square law this is quick and dirty and if you can be more accurate you have some super calibrated lenses and need to calm down

exactly!

[RodKlukas]

to calculate easily get a small tape measure:

Measure the bellows extension from lens board to image plane(ground glass).

Take the focal length of your lens in inches and the extension of your bellows in inches. ie 210mm lens = 8" lens roughly.
bellows extension of 16"or 16.5".
Now using the 8" and 16" measurements think of the 8 and 16 as F-stops.
So the difference between F8 and F16 is 2 stops and that is your compensation.
This is most easily calculated or taken care of by changing your ISO down this amount or in our example, 2 full film speeds. So if using ISO 100 you would simply change your ISO to 25 and you have your answer.
Takes much less time to do than to tell you.
Rod

[Mark Sawyer]

...or just measure the bellows extension and the diameter of the aperture through the front element, then divide the former by the latter. This gives you the actual f/stop at the externsion and aperture your camera and lens are set for.

There are quite a few simple methods, but the books all tell you to divide the square of this by the square of that, which seems unnecessarily complex.

[Doremus Scudder]

Since this is a sticky thread and since I do not see my particular solution (which I thought was standard procedure...), here goes.

1. Figure out bellows extension factors for all your lenses for a set of exposure factors (I use 1.5, 2, 3, 4, 6, 8, 12, 16, and 20, dropping the higher ones as the bellows length is exceeded).

2. Make a chart and carry it with you in the field, along with a small tape measure.

3. When you need to apply a bellows extension factor, measure your bellows extension, look up the factor in the chart for the lens you are using and apply it as you would a filter factor.

Voilá! Done and no fussy calculations needed in the field.

FWIW, I'm attaching the bellows extension factor tables for my lenses for up max bellows extension 16 in/400mm in both inches and mm. Maybe they will be of use to someone.

Best,

Doremus Scudder
www.DoremusScudder