What confuses the hell out of people is mixing the focal length of lenses with the field-of-view. To get the same field-of-view on different formats, you need a different focal length. Take a lens designed for one format and use it on a different one, you'll get a different field-of-view.

In this case, the original post was hoping that a very wide angle lens for 67 would give a very wide angle lens on APSC. It does exactly the opposite. A 45mm lens is very wide angle on 67, but almost a normal lens on 35mm, and a slight telephoto on APSC.

Bjørn's table shows this perfectly. If you want a 87.7 degree field of view, you need a 46mm lens on 67, but a 15mm lens on APS-C. If you attach that 46mm lens to an APSC camera, your field-of-view would be between 39.6 and 31.4 degrees.

A 45mm lens is a 45mm lens on whatever camera you attach it to. So if you want to know the FOV for APSC, put a 45mm lens on it and look. A 45mm lens on 67 has the same FOV as a 24mm lens on 35mm, or a 16mm lens on APSC. Attaching a 45mm lens designed for 67 to APSC doesn't make it a 16mm lens, it is still a 45mm lens albeit with a huge image circle of which you are only using a small section.

Best wishes, Kris.

I've just bought a 90mm large format lens to use on my Horseman 5x4 view camera. I've not used my large format gear nearly often enough partly because my wide-angle lens was a bit of a pain to use. The new lens is much easier, and hopefully I'll start getting more out of my LF set-up. I do use a Pentax loupe, but I don't think that'll allow me to post any images here! One day I'll spring for a Pentax Spotmeter too...

Just a silly photo as I was having some fun with my MX, SMC Pentax "K" 17mm fish-eye lens and some expired Kodak BW400CN film rated at 200. I think I used the built-in orange filter.



Fishy tree par Kris Lockyear, on ipernity

Another example image.


Immanuel Church, New Castle, Delaware par Kris Lockyear, on ipernity

It'll have to wait until the replacement bellows arrive. You could sieve soup with them at the moment!

Kodak folding HawkEye Model B (2) par Kris Lockyear, on ipernity

Whatever the benefits of an IR mirrorless camera, it misses the point somewhat.

Now debating which filter to have fitted...

Thanks all. K.

Thanks guys, I'll check both out.

My K20D has sat unused since I bought my K-3 in 2014. Given the resale value is not very much, I was wondering about getting it converted to IR. Has anyone had a K20D converted? Any tips? Recommended workshops?

Thanks in advance, Kris.