I am a big optics geek

Ok. So I spend more time than I probably should reading articles and forums about photography. And the weird thing is that ever since digital cameras have come along, it seems like every photographer _everywhere_ has forgotten the basic optical principles that they learned back in Photo1. Namely – people are buying into marketing hype that tells them focal length somehow determines the fundamental look and feel of a photograph. Well, I’m here to prove ’em all wrong.

Please, read on, and be amazed by how much time I can waste when I want to prove a point.

Here’s what I did – I stuck my camera on a tripod, pointed the camera at my backyard, and took 11 frames at a variety of focal lengths. Then I looked at the most telephoto of the shots, and cropped all the others to match it. Now, I cropped them unscientifically and the naysayers will point out that the frames are not _exactly_ alike. To them, I say – if you want to do it scientifically go ahead, it’s a real PITA. Eyeballing the crops should still prove the point – the massive change in “perspective” that people claim they see switching from a 35mm “normal” lens on a DX-sized sensor to a 50mm “normal” lens on a 35mm-sized sensor is simply not there, it’s a myth. (And most of the differences can be explained just by realizing that I botched the crop on a few frames, notably 20mm and 24mm)

Oh – the overall crappiness of the WA shots is because they are enlarged from truly tiny bits of a 4mp frame.

Brace yourself for a big pile of images proving my point… Here goes!

The full sceneThis is the full scene @ 12mm with the crop marked in red
12mm 12mm
18mm15mm
18mm
20mm20mm
24mm24mm28mm28mm35mm35mm
50mm50mm
70mm70mm
85mm85mm
120mm120mm

2 thoughts on “I am a big optics geek

  1. I really enjoyed this sequence of photographs, and it really illustrates the benefit of matching the lens focal length to the field of view , that is required. One interesting topic that you might like to explore is the relative quality of a fixed focus camera lens, compared with a zoom lens set at the same focal length.

  2. Thanks Brian!

    I’m not sure I own a suitable set of primes to do a useful test like you mentioned, though it could be interesting to compare, say, my 50mm 1.4 with 50mm of my 24-85, 18-200, 28-70…

    The truth of it all is that it would depend a lot on the particular lens in question – A high-end 2.8 zoom might outperform a low-end third-party prime, for instance.

    Generally speaking, a prime _should_ be a little sharper, and offer nicer bokeh than a zoom set to the same focal length, but you never know until you try a particular combination.

    For my part, I am totally in love with my 50/1.4 and my 85/1.8, but they are the only primes I use with any regularity (well, the 60/2.8 micro too, but it’s rather specialized.)

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