View Full Version : Coverage at 1:1 - double ?

Ken Lee
2-Oct-2005, 17:32
Lens coverage figures are often given for f/22 at infinity. To focus at 1:1, we need twice the focal length.

Does this mean that we get a circle of coverage whose diameter is twice the stated infinity coverage ?

So while a 180mm Fujinon A is said to give 252mm coverage at infinity and f/22, will it give 404mm at f/22, when focused at 1:1 ? If that is the case, would it not make a good closeup lens for 8x10 ?

Ron Marshall
2-Oct-2005, 17:34
Yes, twice as much. Simple geometry with similar triangles

Leonard Evens
2-Oct-2005, 20:24
What remains fixed is the angle of coverage. So if you double the distance from the lens to the film, you double the diameter of the circle of coverage.

Michael Kadillak
3-Oct-2005, 07:19
Give it a go and let us know what you find. I have the same Fuji lens and the prospect sounds promising.


Ken Lee
3-Oct-2005, 09:19
Shucks - I used to have a 180A for use on 4x5 - but sold it when I moved up, thinking that I had no use for it any longer.

Duhh... We live and learn.

Ken Lee
3-Oct-2005, 09:28
I kept my 240A and use it for close work on 5x7 and 8x10: flowers, leaves, etc. The 400mm+ of necessary extension is not a problem on the 8x10 Shen Hao, but it reaches the limit of my old 5x7 Kodak. A 180 or 150 would be much easier, and would still give enormous coverage.

Perhaps others out there were aware of this, and have some nice images to share. 1:1 on 8x10 isn't all that small - but the images be rather nice when they "come out right".