Angle of view for Pentax M lenses

I have a small collection of SMC M lenses, but can't find any info on angle of view for them on the web. Possibly it exists in the catalogues of the time (which I don't have)
Does anyone have angle of view for SMC M:
24mm f2.8
28mm f3.5
50mm f1.7
135mm f3.5

.. before I get the matchsticks, the blue tack and the protractor out?

Thanks!

update - sorry the 24mm is SMC not 'M'

Generic list, but this any help?

http://www.sizes.com/tools/ang35still.htm

do you mean when used on a 35mm camera (as originally intended), or when used on an APS-C DSLR such as the K20D?

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you don't have to be mad to post here



but it does help

Thanks very much
This is a good site (but a weird one!) and it may explain why I'm have got confused info before - WHY would anyone need to know what the diagonal AOV was?

Reason for the question is, of course, that I use film and a 1.5 crop, plus some other lenses, and it's easier to recce with a protractor and a note book and come back when the light might be good, with the right lenses....

good idea, I always used to carry my digital compact around with me and take snapshots if I saw a photo I wanted to take. That way I could come back later with the "big guns" and at a sensible time for the light.

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you don't have to be mad to post here



but it does help

There's a page on Wikipedia which simplifies this: link. You can use the formula


to determine the focal length of any lens

Hope that helps!

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My Photobucket

24mm f2.8 - 84 degrees
28mm f3.5 - 75
50mm f1.7 - 47
135mm f3.5 - 18

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Best regards, John

Thanks folks (I put a response on this, but it disappeared somewhere. Try again...)

I realise now (belatedly, and thanks to the responses/docs in this thread) that some (all?) manufacturers - including Pentax and Sigma - use the DIAGONAL for the angle of view spec.

This probably makes sense for Medium Format as the size/shape of the image size can change (6x7, 645, etc etc - also makes sense if you went to art school and take funky slanted horizons, or prefer headless horse pictures ).

Anyways, I now have the means to update my measurements for 35mm and APS-C - just need to rework my Px67, because I reckon the ones I have are diags too ('square on the hypotenuse' rings a bell; I'll look it u on Wiki).

So if you notice someone wandering about between 10 and 2 with a protactor (possibly wearing shiney shoes) I'll be back at some point with the right lens and wearing boots )

Yes, the diagonal is always the measurement given.

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Best regards, John

aha! as I thought! (and so recently )

This does back up the theory that buildings do not get bigger (or move) between the recce and the final tripod set up

I guess it the logic of the people who make the lenses v the logic of using them - just quirky enough to confuse you.

Thanks John!

Given the angle of view for the diagonal, work it out by proportion for the width and height of the frame format, if you need that info!

For 35mm frame: Diagonal = 43mm, height = 24mm, width = 36mm

Given the angle for diagonal = 84 degrees (24mm lens)

Angle for width = 36/43 x 84 = 70 degrees.
Angle for height = 24/43 x 84 = 47 degrees.

For the other lenses substitute the lenses' diagonal angle in the formula above.

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jas