Bellows Draw For 480mm Lens.?

[tgtaylor]

How much bellows draw is required for a 480mm lens on a 8x10 camera for ordinary photography - not 1to1?

Thomas

[John O'Connell]

Short answer: 580mm, or 23".

Long answer: it depends. I rarely shoot at infinity, and I always make sure I have enough bellows to get to 1:3 on 8x10 with any lens. Portraits on 8x10 require serious bellows extension unless you're doing full-length poses.

[tgtaylor]

How did you arrive at that calculation John? Add 100mm to the focal length of the lens?

Thomas

[Mark Barendt]

Roughly 480mm from lens board to film should get you infinity focus.

I say roughly because the exact point in the lens where 480 falls may be slightly forward of or behind the board. For a telephoto lens the board will be considerably behind the 480mm mark.

To focus on subjects closer to the camera than infinity you need to move the lens farther from the film, how much depends on how close the subject is.

960mm from board to film (2x focal length) is roughly where you reach 1:1

[John O'Connell]

How did you arrive at that calculation John? Add 100mm to the focal length of the lens?

Thomas

The rule of thumb is that your bellows draw has to be 1.2x the focal length of the lens for general photography. I find it to be a poor rule of thumb, though, as I do portraits.

Judging by your Flickr page, you'd probably make out all right using the rule of thumb.

[tgtaylor]

Thanks.

I have a 480mm being delivered tomorrow and I'm guessing that I have another 120mm or so of bellows beyond what I use for the 360mm.

Thomas

[Ken Lee]

You might find this short article interesting, entitled Formulae for Bellows Extension and Compensation (http://www.kenleegallery.com/html/tech/bellows.php).

It covers this and other related questions.

[Tim Povlick]

>>How much bellows draw is required for a 480mm lens on a 8x10 camera for ordinary photography

420mm

Measured from back of lens board (GG side) to ground glass. Lens - Schneider 480/8.4 Symmar-L

Kindest Regards,

Tim

[tgtaylor]

Thanks guys! I just measured the bellows and have 25" or 635mm from the lensboard to where the film holder slides in and can get another 2.5" or 698mm total by extending the front and rear focus all the way. I shouldn't have any problem using the 480mm lens on this camera.

Now I'm off to look for a soft case for transport.

Thomas