How much bellow-extension do I need?

[ThePenguin]

Is there some sort of formula to calculate how much bellow-extension you need?

Take this example (on 8x10):

How much do I need the bellows to extend if I'm going to focus on something that is 2m away with a 480mm lens?

Is there a formula to calculate this?

[Greg Lockrey]

FD= (SDxFL)/(SD-FL)

Focal Distance= (Subject distance x Focal Length)/(Subject Distance - Focal Length)

FD= (2mx480mm)/(2m-480mm)=960000mm/1520mm=631.58mm

[IanG]

Camera's were sold as Double or Triple extension, that's bellows extension that extends 2 or 3 times the normal focal lenght for the format, in the case of a 10x8 camera that's a 300mm/12" lens.

Most 10x8 cameras have at least double extension, in the case of an Agfa Ansco 10x8 it's 27.5" 70cm on the more basic models.

Ian

[ThePenguin]

Great, thank you!

[Lynn Jones]

Magnification plus one times focal length = bellows draw.

Lynn

[Emmanuel BIGLER]

... and (inverse magnification plus one) times focal length = distance from camera to subject.

[banjo]

to make it easy if you have 480 mm that infinty no movemunt 480 x 2 is double extension 480 x 3 triple I can't remamber but I thank you need double extension
for a 1 to 1

[ThePenguin]

Allright, but if we do it the other way, how much bellow-extension do I need if I wanna shoot with a 210 on infinity?

[unixrevolution]

Allright, but if we do it the other way, how much bellow-extension do I need if I wanna shoot with a 210 on infinity?

Infinity focus extension = focal length, so 210mm.

[banjo]

yes Infinity focus extension = focal length, so 210mm
but for any thing closer then Infinity is when bellows extension
is needed. so for a 1 to 1 you will need 420mm that would be as
close as about 2'. for a head & shoulder or for focus at 8' you will
need about 260mm

[Emmanuel BIGLER]

Infinity focus extension = focal length,

Well, this is true for most view camera lenses of quasi-symmetrical design, but there are exceptions for telephoto designs for wich the so-called flange-focal distance, the data that you actually need to know in order to focus at infinity, is much shorter than the focal length.

For example with a 360mm tele-arton, the flange-focal distance is equal to 209 mm, this is your approx bellows draw at inifinity.
There was a 180 mm tele Arton with 115mm of flange focal distance (designed as a compact long focal length for 6x9 cameras like the baby technika)

But, yes, any lens of quasi-symmetrical design like tessar-type 4/3 or triplet 3/3 lenses, plasmat 6/4, dialyte 4/4, symmetrical wide-angle view camera lenses etc ... have a flange focal distance close to the focal length.

[Cor]

Infinity focus extension = focal length,

Well, this is true for most view camera lenses of quasi-symmetrical design, but there are exceptions for telephoto designs for wich the so-called flange-focal distance, the data that you actually need to know in order to focus at infinity, is much shorter than the focal length.

For example with a 360mm tele-arton, the flange-focal distance is equal to 209 mm, this is your approx bellows draw at inifinity.
There was a 180 mm tele Arton with 115mm of flange focal distance (designed as a compact long focal length for 6x9 cameras like the baby technika)

But, yes, any lens of quasi-symmetrical design like tessar-type 4/3 or triplet 3/3 lenses, plasmat 6/4, dialyte 4/4, symmetrical wide-angle view camera lenses etc ... have a flange focal distance close to the focal length.

And while we are getting correctly getting precise, let's not forget the older convertible lenses (such as Symmars), when you remove the front element to obtain the longer lens (ie the Symmar150/265 mm) you need MORE bellows length than you would expect..

Best,

Cor

[banjo]

yes with a Symmar150/265 mm you would need about 400mm
bellows for the 150mm
And would need oh say 575mm for the 265mm
Good point the flange-focal distance is the starting point then x 2 + 50mm
for good closeups

[Cor]

yes with a Symmar150/265 mm you would need about 400mm
bellows for the 150mm
And would need oh say 575mm for the 265mm
Good point the flange-focal distance is the starting point then x 2 + 50mm
for good closeups

Well IMHO it is not that bad..in the 150 configuration no funny things, ie infinity is around 150 cm ground glass to lens, things get different in the 265mm configuration, for infinity I need almost max bellows on my Tech III which is I think 30-35 cm (have to measure it at home to be sure)..

Best,

Cor

[AnselAvedon]

Hey I am having a bit of trouble with this. I'm getting a negative number and think it might not be possible to focus close however as the last person wanted to focus 2mm away I don't think that is the problem but rather the lens length I am trying to use. Maybe.

I'm trying to photograph an hand cracking an Egg with my 8x10.

I recently acquired a second rear standard and a 600 800 and 1200mm lens set and am trying to figure out how much bellows I will need to shoot the egg and hand.

I measured the hand and egg to be 4 inches so to fill the frame the magnification will have to be 2.5 yep good first equations a bit easy. Now the tricky part

I want to shoot 1 foot away from the lens that is 304.8mm

I want to know the maximum bellows I could need to shoot with 1200mm

The math I used is (304.8x1200) 365760 / (304.8-1200) -895.2*heres where I think I'm having the problem.

365760 / -895.2 = -408.57


please help I know yes it would be easier to use the 600mm or even my 240mm but is it not a bad ideal to have the capability to be able to utilize all of the lenses.

[Tin Can]

Read this thread. You won't be using a 1200 mm lens.

http://www.largeformatphotography.info/forum/showthread.php?76719-Macro-Lens-8x10-for-2-1-5-1&p=733806&viewfull=1#post733806

[Dan Fromm]

Hey I am having a bit of trouble with this. I'm getting a negative number and think it might not be possible to focus close however as the last person wanted to focus 2mm away I don't think that is the problem but rather the lens length I am trying to use. Maybe.

I'm trying to photograph an hand cracking an Egg with my 8x10.

I recently acquired a second rear standard and a 600 800 and 1200mm lens set and am trying to figure out how much bellows I will need to shoot the egg and hand.

I measured the hand and egg to be 4 inches so to fill the frame the magnification will have to be 2.5 yep good first equations a bit easy. Now the tricky part

I want to shoot 1 foot away from the lens that is 304.8mm

Impossible. What you mean by "1 foot away from the lens" isn't clear. If the distance from the lens' front node -- approximately at the diaphragm for most, not all, LF lenses -- then the film plane will have to be infinitely far behind the lens. If you want to shoot at 2.5:1 with a 305 mm lens the front node will have to be ~ 420 mm from the subject and the rear node, also usually near the diaphragm, will have to be ~ 1050 mm from the film plane. Since extension is traditionally measured from the lens board and I don't know how your lens is mounted, the extension you need will be a little different from 1050 mm.


I want to know the maximum bellows I could need to shoot with 1200mm

If you shoot at 2.5:1 with a 1200, multiply the distances I gave you by 4. ~ 1700 mm and ~ 4200 mm. You'll need a looooong monorail and bellows to do what you want with a 1200.

[Pfsor]

I recently acquired a second rear standard and a 600 800 and 1200mm lens set and am trying to figure out how much bellows I will need to shoot the egg and hand.



Ehm, in your case it would be much better to try to figure the bellows extension first and buy the lens afterwards, me thinks. Otherwise you shoot yourself to your foot. Just my 2 cents.

[Pfsor]

...
please help I know yes it would be easier to use the 600mm or even my 240mm but is it not a bad ideal to have the capability to be able to utilize all of the lenses.

Except that there are horses for courses. Trying macro photography at 2.5 :1 with 1200mm lens means you don't have the "capability to be able" to utilize your lens for this course.