# Thread: How do you work out what a lens can cover

1. ## How do you work out what a lens can cover

Hi
How do you work out what format a lens can cover, is there a website, or do you multiply something by something.

Regards
David

2. ## Re: How do you work out what a lens can cover

Scroll down to "Comparison Charts" on the home page of this website.

Click on the format you are seeking, and you'll find the answer to your inquiry.

There is a gold mine of information available on that page.

3. ## Re: How do you work out what a lens can cover

Originally Posted by David Woods
Hi
How do you work out what format a lens can cover, is there a website, or do you multiply something by something.

Regards
David
David,

The optical formula is as follows:

2 x tan(claimed coverage angle x 0.5) x focal length of lens. For example, a Rodenstock 360mm Apo-Sironar-S with a 75° coverage angle at f/22 would be: 2 x tan(75/2) x 360 = 2 x 0.7673 x 360 = 552mm.

Obviously, the coverage angle varies widely from lens to lens, manufacturer to manufacturer and the most deadly - the defintion of "sharply covered". Therefore "claimed" to "actual" is best determined by "to taste" testing yourself.

Have fun and good luck!
Carver

4. ## Re: How do you work out what a lens can cover

http://www.ebonycamera.com/articles/lenses.html

WWW.timeandlight.com

5. ## Re: How do you work out what a lens can cover

Originally Posted by David Woods
Hi
How do you work out what format a lens can cover, is there a website, or do you multiply something by something.

Regards
David
Usually the manufacturer provides this information; there is nothing to calculate if an image circle is given. You should be able to figure if your film diagonal is less than the image circle diameter in your head.

Otherwise, if no manufacturer info is available, you use trial and error to see what the coverage is.

6. so what am I finding when I look through the clipped corners of my groundglass and make sure that the iris opening is visible and round with no vignetting? is it illumination only? thanks

Thanks John

David

8. ## Re: How do you work out what a lens can cover

Originally Posted by Andrea Gazzoni
so what am I finding when I look through the clipped corners of my groundglass and make sure that the iris opening is visible and round with no vignetting? is it illumination only? thanks
what I am saying is, if I look at a lens and say for example it is a 300mm lens with a 6.3, is there a way of working it out myself, without having to go to websites, or having to ask anyone.

David

9. ## Re: How do you work out what a lens can cover

Originally Posted by David Woods
what I am saying is, if I look at a lens and say for example it is a 300mm lens with a 6.3, is there a way of working it out myself, without having to go to websites, or having to ask anyone.

David

Explanation: Angle of coverage depends on the lens construction (and personal taste), sowithout knowing what kind of lens it is there's no way of knowing. A 300mm f:6.3 telephoto lens might not even cover 4x5", while a 300mm f:6.3 wide angle could cover 20x30".

Most f:6.3 300mm lenses are "normal lenses", but the difference between a Tessar-type (just covers 8x10") and a Plasmat-type (covers 11x14") means there's still no way of working it out without tables - or experimentation.

10. ## Re: How do you work out what a lens can cover

Originally Posted by Ole Tjugen

Explanation: Angle of coverage depends on the lens construction (and personal taste), sowithout knowing what kind of lens it is there's no way of knowing. A 300mm f:6.3 telephoto lens might not even cover 4x5", while a 300mm f:6.3 wide angle could cover 20x30".

Most f:6.3 300mm lenses are "normal lenses", but the difference between a Tessar-type (just covers 8x10") and a Plasmat-type (covers 11x14") means there's still no way of working it out without tables - or experimentation.

thanks Ole

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