210 with 12" bellows..how close?

Hi, I am new here and to LF..

I do portrait work, and I would like the option to do a tight shot of a face where the just the head fills the frame. How many inches of extension would I need with a 210 for this?

Alternately, would a 250 or something make more sense to achieve this? I want to have the choice to shoot the range from full body shots, up to tight face shots.

thanks!

(I've been looking at different field cameras, and the ones in my budget seem mostly to have only around 12" bellows extension..)

i should clarify I am going to be doing the portraits in the field, which is why I am looking at field cameras..

12" of extension with a 210mm lens gets you to an image height of a bit more than 10" on 4x5. It'll work just fine for a close headshot.

A field camera is less than ideal for such work because you have to shift the subject or the tripod to crop, rather than having the option of slipping the tripod block down the monorail, but it shouldn't be a huge issue in practice.

hi John, my head is about 10" from chin to top of head, so that's what I could get? Sorry to be redundant, just need to be certain before I buy..

1/210=1/u+1/300, u=1/(1/210-1/300)=700mm, and the length of the film is 5", so you can get 5"*7/3=11.67" long head.

It is easy to compute.
The additional bellows extension with respect to the focal plane depends only on the magnification factor and the focal length :
extension = magnification x focal length
Imagine that you fill a 250mm length of head inside a 125 mm length of 4x5" film in "portrait" orientation.
Then the magnification factor is .5 whatever your focal length might be.
The additional bellows draw is half the focal length of your lens whatever the focal length might be.

So with a 210mm you'll need 105 mm of extra rail length with respect to the infinity-focus position.
Plus about 210mm of back focal distance if you do not use a telephoto this makes a total of 315 mm. 12" is 305 mm. So you'll make it roughly if you have 12" of total rail length.
However, in this position the subject will be located at 630 mm of the lens, about 25", about 2 feet. This is quite close for a classical portrait. EIther you should frame less tightly or use a longer focal length.
With a 250mm, again at a magnification ratio of .5 you'll need a total of 250+125 = 375mm. For this you need 15" of total length.
Or a telephoto which has a shorter infinity-focus bellows draw. The extension needed to reach a magnification of .5 however is unchanged for any type of lens of the same focal length.

Quote:

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Originally Posted by emcd

(I've been looking at different field cameras, and the ones in my budget seem mostly to have only around 12" bellows extension..)

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Get an older 5x7 with a 4x5 back. You'll have more bellows at the expense of added weight.

The Wista Extension Lensboard Set works on any camera with a 4x5 Technika style lensboard. It would then give you more useable extension.

My 210 is on a modified Sinar recessed lens boardl, used back to front & re-cut to fit my Wista. Works well the extra few millimetres makes a big difference.

Ian