hyperfocal on 4x5?

[T. E.]

I was looking at the Badger site and noticed they will be carrying a Fotoman 4x5 starting in April. The are describing it as a "point and shoot" (which I am guessing means no movements?) with a focusing cone mount and working with wide angle Schneider XL lenses. Since I shoot landscapes am really only interested in a huge dof anyway I was wondering about hyperfocal distance on large format lenses on a camera like this.

I know with a 28mm lens on a 35mm camera at f/22 I can hyperfocal about 2.5' to infinity. With a 45mm lens on a 645 at f/22 it is about 5' to infinity (both allowing for some error) both show about the same view. What about a 90mm on a 4x5?

Presuming shooting at the smallest f-stop (usually f/45 on the really wides) what could you hyperfocal on the 47XL, 58XL, 80XL and 90XL?

I would think a 47XL might be down to two feet to infinity (I know the view would be a lot wider than the 35mm or 645 image).

Thanks.

[Nick_3536]

Go to the Scheinder website and download the DOF charts. Or you could try any of the DOF calculators on the web.

[Edward (Halifax,NS)]

The 47mm will give you 2ft to infinity at f/22

The 90mm will give you 6.5 ft to infinity at f/22
or 4.5ft to infinity at f/32

[Chris Ellinger]

Here's a calculator:

http://tangentsoft.net/fcalc/

[Emmanuel BIGLER]

The hyperfocal is not intrinsic to a lens+aperture not even to a lens+format+aperture combination. If your goal is only to take 4"x5" contact prints you'll not consider the same acceptable out of focus un-sharpness as if your goal is big enlargements of 4x5 feet size ...
So the best IMHO is to re-compute your own set of hyperfocal distances, the only fuzzy parameter is the acceptable circle of least confusion "c". A good starting value is something twice what is used in medium format i.e. c=90 to c=100 microns. in medium format traditional DOF scales consider c=40 to 60 microns which is not very stringent.
The hyperfocal formula is simply H = f*f/(N*c) where H is the hyperfocal distance, F is the focal length, N the f-number and c the circle of confusion.
If you only need 4"x5" contact prints seen from a 10" distance, you can take something less stringent for c, for example take c= 200 microns but you probably won't be satisfied by this.
For a 12X = 4feetx5feet enlargement size... you have to decide from how far the print is to be examined.
If the image is eventually scanned and printed at 300 dpi on paper enlarged twice this yields another criterion. 300 dpi is 84 microns per dot, from a 2X enlargement you need 41 micron per point on your original, if we equal this figure to a "c" value, the requirement is more stringent than usual DOF scales for 4"x5".
The other figure that can help about finding a proper c-value is the angular resolution of the human eye, something between 1/3000 and 1/1500. 1/1720 is the traditional value, equal in radians to two minutes of arc. This rule of 2 minutes or arc = 1/1720 radians yields c= 45microns in 6x6 camera format for a 8"x10" print seen from a distance equal to the diagonal i.e. 12", in 6x9 we get c=60 microns and in 4"x5" (image diagonal = 150mm) we get c= 90 microns.

[John Hoang]

Here is the link with a calculator to use on your Windows, Palm Pilot , or assemble one to take with you to the field.

www.dofmaster.com/ (http://www.dofmaster.com/)

[Ole Tjugen]

Before you get too deeply into Hyperfocal mathematics, I suggest you read Harold Merklinger's article/book about this: www.trenholm.org/hmmerk/#TIAOOF (http://www.trenholm.org/hmmerk/#TIAOOF)