Determining Petzval lens coverage

[Glen Seelenbrandt]

At some point I am hoping to purchase a Petzval formula lens to shoot with my Graflex Super Graphic. I am still trying to figure out how to determine if the lenses I am looking at will cover the full 4x5. Since many of the folks selling these types of lenses on eBay rarely list focus distances, is there a formula you can follow based on lens measurements? or even on focus distance for that matter? Any help would be greatly appreciated. Thanks!

[seven]

with Petval lenses the FL is roughly equal to the diameter of image circle. 4x5" diagonal is 6.4" or 162mm, try looking for a lens with such or bigger FL.

[Glen Seelenbrandt]

Thanks seven! That's some great info. I also read somewhere that the physical length of the lens might also relate to the focal length as well. Eg: A 5 inch lens has 5 inch focal length. Is there any truth to this?

Thanks again!

[seven]

i don't think so. maybe on some lenses it is. on all Petzvals i have seen or own FL is bigger than physical length.

[goamules]

I can be a rough approximation. A 6" long one is often 6" FL. But as the physical length gets a little longer, the FL can get a lot longer. A 10" long Vitax Petzval has a 16" focal length, for example.