Bellows extension

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MattKing

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Rod Klukas

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Clever, or just fortuitous? :D
Here is a simple formula I taught my students in large Format Photography. Take the focal length of your lens in inches say a 150mm(6 inches) and measure bellows extension with a tape measure--say 12 inches-- and because i said so change the unit of measure to aperture so you have F6(5.6 + 1/3) and F12(F 11 and + 1/3)Now ask what is the number of stops difference? 2 stops in this example. So that is what you need to compensate. So go 2 stops slower on shutter speed in this case. By the way, any time your extension is double the focal length you are at life size reproduction. Also the distance from the shutter to the subject should be approximately the same in this example, 12 inches away.
At 1.5 times focal length for extension, you are at 1/2 life size. Compensation in this scenario is 1 stop.
Hope this is helpful. It has worked for a quick exposure adjustment for 30 + years
 

markbau

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This is probably a stupid question (and probably a bit off topic) but how does a MF or 35mm camera lens not need an exposure factor when you are focusing something very closely and the lens front element is much farther from the film plane than when at infinity?
 

David A. Goldfarb

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This is probably a stupid question (and probably a bit off topic) but how does a MF or 35mm camera lens not need an exposure factor when you are focusing something very closely and the lens front element is much farther from the film plane than when at infinity?

A camera with TTL metering compensates automatically by reading the light that comes through the lens. If you use an external meter, then you need to calculate exposure factor. Also, exposure factor becomes relevant when the image-to-object size ratio is 1:10, so the smaller the format, the less likely you are to be in the range where exposure factor is relevant.
 

138S

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but how does a MF or 35mm camera lens not need an exposure factor ...?

Adding to the previous answer...

Some MF cameras require bellows compensation, it is the case of the Mamiya RB67, see next picture with the correction factor for each focal and for each extension:

mam.jpg


A lens can be of Unit Focus design, like Nikon 50mm f/1.8. As you focus closer the magnification increases (focus breathing) as all the glass goes farther from the body, like in LF cameras, but as David pointed this is overcomend with TTL metering, with no Factor needed.

Other lenses like Nikon 50mm f/1.4 are of Internal Focus type, a certain glass displaces inside the lens to focus near, but magnification may not vary much.
 

Rod Klukas

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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.
Adding to the previous answer...

Some MF cameras require bellows compensation, it is the case of the Mamiya RB67, see next picture with the correction factor for each focal and for each extension:

View attachment 249465


A lens can be of Unit Focus design, like Nikon 50mm f/1.8. As you focus closer the magnification increases (focus breathing) as all the glass goes farther from the body, like in LF cameras, but as David pointed this is overcomend with TTL metering, with no Factor needed.

Other lenses like Nikon 50mm f/1.4 are of Internal Focus type, a certain glass displaces inside the lens to focus near, but magnification may not vary much.
 

Rod Klukas

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With large format I came up with a method making it very easy. First get a small pocket 3-6 foot imperial or feet, tape measure. Next make a note of your lens focal length loosely converted to inches. i.e. 210mm = 8.25" , 90mm = 3.5", 80mm = 3.2, 150mm = 6"

after seeing focus for your closeup, measure the bellows in inches. For example a 210mm lens and the extension is 16". Change both to inches so we have a 8" lens and and 16" extension. Change the unit from inches to Aperture. So we have F8 and F16.

How much difference is that? F8 to F11 is one stop, F11 to F16 is another stop, so we need 2 stops in compensation.

Another example: 135mm lens = 5.6" and say a 13" extension or F13. So we have 1 stop from 5.6 to F8, and 1 stop from F8 to F11 and about 1/2 stop more to F13(F13.5 is the half stop). So we need 2.5 stops of compensation so we go 2 slower shutter speeds and 1/2 stop more open in apertures. All done. BTW, if the extension is double the focal length of the lens, the compensation is always 2 stops and you are at life size, and subject will be the same distance from the shutter on the lens as the shutter to the ground glass or film plane.

Hope this helps someone.
 

138S

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With large format I came up with a method making it very easy.

Rodenstock_260700_Depth_of_Field_Calculator_1533144049_155145.jpg

Also we have the Rodenstock Pocket Calculator, that Bob always recommended. It calculates many things with "style", also the compensation, new it's a bit expensive but it can be found used for the half.
 

xkaes

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I was unaware that the Rodenstock Calculator computed bellows extension compensation.

I made a tape -- that displays the amount of compensation needed for my specific lenses -- when stretched from the front to rear standard.

Keep in mind that bellows extension compensation can vary substantially for many wide-angle and tele-photo lenses -- which typically have flange focal lengths different from the optical focal length. For example, if you are shooting 1:1 with a 75mm lens -- with a flange focal length of 85mm -- 150mm of bellows will not produce 1:1, and your exposure compensation will need adjustment..
 

Bob S

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I was unaware that the Rodenstock Calculator computed bellows extension compensation.

I made a tape -- that displays the amount of compensation needed for my specific lenses -- when stretched from the front to rear standard.

Keep in mind that bellows extension compensation can vary substantially for many wide-angle and tele-photo lenses -- which typically have flange focal lengths different from the optical focal length. For example, if you are shooting 1:1 with a 75mm lens -- with a flange focal length of 85mm -- 150mm of bellows will not produce 1:1, and your exposure compensation will need adjustment..

Immaterial with the Rodenstock calculator. It measures magnification before it calculates. It also gives exposure correction for the calculated magnification.
 

RalphLambrecht

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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.

You don't have to worry about it until you get into too close-up photography
 

jwd722

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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.
If you have a Gossen Luna Pro SBC you can let the meter do the heavy lifting for you. Pages 29-31 explain how to use the meter dials to set a direct readout of corrected exposure values and another method for a corrected aperture only.

If you don't have a Luna Pro SBC this may be a good reason to get one. Owners manual can be found at butkus.org
 

xkaes

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Immaterial with the Rodenstock calculator. It measures magnification before it calculates. It also gives exposure correction for the calculated magnification.

Good luck figuring out magnification -- I know how to do it, but it's a PITA.
 

Rod Klukas

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The easiest way to do compensation is this: First use a pocket tape measure to measure your extension in inches. Next change your lens focal length to inches.

Now because you think I know what I am doing change the numbers from inches to Apertures.

So a 150mm lens and (6 inches,) and a 12 inch extension.

F 6(5.6 and 1/3) Extended to F12 (F11 1/3). What is the difference? 2 stops. Voila.
----
180mm = 7.5 inches and if extended to 11 inches.

F7.5 (F 5.6 and 2/3) and 11" (F11) 1 1/3 stops.

In either case adjust shutter speeds for full stops, and apertures for small increments. You may have to go one stop slower on shutter and back up aperture for closest settings.

The old guys from the 1940's and 1950's taught me this as most lenses used to have the focal length in inches.

Hope you find this helpful.

Rod
 
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Eff64

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Klukas is right, and he posted this twice. KISS

I used the same system for many years when doing copy work at our commercial studio. It always gave an accurate exposure.
 

ole-squint

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I agree tnat Eric's method is the easiest. Say you have an 8" lens. You extend the bellows to 16". 16x16=256. 8x8=64. 256 divided by 64 equals 4, so 4 times your exposure at 16 inches. 2 times your exposure at 12 inches (halfway in between), 1 1/2 times your exposure at 10 inches. All you need is some sort of tape measure in your camera bag.
 

grahamp

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Fabric tape measures are good, but marking up a free edge of the dark cloth with inch and thirds works. The most you need to is the maximum bellows extension. If push comes to shove, my hand span is 9 inches, and I can estimate from that :cool:

The inches to f-stop method is easy to do - there is an f-stop table on every lens!
 

Eff64

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I agree tnat Eric's method is the easiest. Say you have an 8" lens. You extend the bellows to 16". 16x16=256. 8x8=64. 256 divided by 64 equals 4, so 4 times your exposure at 16 inches. 2 times your exposure at 12 inches (halfway in between), 1 1/2 times your exposure at 10 inches. All you need is some sort of tape measure in your camera bag.

Don’t agree.

Using the example you gave, 8” lens, measuring the lens board to the film plane, 11” is 1 stop, 16” is 2 stops. Anything in between you approximate. 12” is technically more than 1 stop.
 

maltfalc

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Fabric tape measures are good, but marking up a free edge of the dark cloth with inch and thirds works. The most you need to is the maximum bellows extension. If push comes to shove, my hand span is 9 inches, and I can estimate from that :cool:

The inches to f-stop method is easy to do - there is an f-stop table on every lens!

get a tiny metric keychain tape measure, mount it to the side of your rear standard and mount a small clip to your front standard. set your front standard to infinity focus, extend the tape to your lens's focal length and clip it to the front standard. now the tape will automatically show the exact focal length you're currently at.
 
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Here's a device you can printout and use to make the determinations. I've only used it for a dry run which seems to work.
 
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I have a question. Which lens is best for closeups and macros? I have 75mm, 90mm, 150mm, and 300mm on a 4x5 camera with 350mm longest bellows extension?
 

FotoD

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I'd go with the 150mm for close-ups at magnifications no greater than about 1.3 (1.3:1).

For larger magnifications I'd prefer a lens made for smaller formats. For example a 105mm f/4.5 enlarging lens should work fine between 1 and 2.3. And a 75mm lens would magnify 4.7 times at the most.
 

grahamp

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While a shorter focal length gets you more magnification for a given lens extension, it also means a closer distance to the subject. This can require special lighting to compensate for the camera/lens getting in the way. So sometimes a longer lens (and more bellows extension for a given magnification) is a better option. It depends on the subject and conditions. There never seems to be a 'best' option. An optimum one based on available equipment and conditions, possibly.
 

ole-squint

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Don’t agree.

Using the example you gave, 8” lens, measuring the lens board to the film plane, 11” is 1 stop, 16” is 2 stops. Anything in between you approximate. 12” is technically more than 1 stop.
And 11" is technically less than 1 stop. One stop from 8" is 11.2". Given the amount of latitude in films and the "acceptable" tolerances of marked shutter speeds, I'm not going to get worked up over it.
 
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