petzval coverage question

[alex from holland]

Hi All,

What focallenght do i need to cover a 20 x 20 inch plate with a petzval ?
Some darker corners is no problem, but i don't want a "half black" plate.

thyanks

alex

[CCHarrison]

Alex,

Its going to take a BIG lens to cover 20x20, somewhere in the 30 to 40 inch focal length range. Dallmeyer 6A may do it, Dallmeyer 7D may... I am sure you will get more great answers, but be prepared to fork out some dough. Good luck.

Dan

The image is of a HBH 22" Focal length Petzval (covered 11x14)

[Wimpler]

Alex, it is much much easier (bellows draw and lens size/weight) and cheaper to use lenses that have a larger image circle so that you can use a shorter focal length then what would be needed for a petzval design.

Also, have you considered shooting on a smaller format (5x7 or 8x10) and enlarging? That makes things easier as well

I'm gonna go check wether I have anything that covers this insane format, but I doubt it.

[alex from holland]

Wimpler,

i know. i shoot on 8x 10 but with collodion and positive.
My next camera will be 20 x 20 inch so need a bigger lens for that.
I have several other lenses like a 26 inch Hermagis aplanat but i also want to use a petzval.

alex

[Steven Tribe]

Dallmeyer say 6A, 7D &, of course 8D! 6D will give corner problens. Otherwise a RR around 30".

[eddie]

25 to 30 inch depending on size. I got just what u need.

[alex from holland]

25 to 30 inch depending on size. I got just what u need.

I know, but that's going to be just a little toooooooooooooo expensive