DA* 55mm versus D FA 28-105mm, on K-1

Started Jul 2, 2016 | Discussions thread
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Barry Pearson
Barry Pearson Veteran Member • Posts: 8,723
DA* 55mm versus D FA 28-105mm, on K-1

DA* 55mm f/1.4

I've had the DA* 55mm for more than four years. I've used it a lot for studio work (see below) and in low light conditions.

On APS-C I get the sharpness I want at f/4, it stays sharp at f/5.6, and I don't use it smaller than that because that isn't why I would put it on a camera.

Although it isn't in Ricoh's "official" list of full-frame lenses, it is well known to have FF coverage. But at what apertures?

I did simple tests, (which I'll explain in detail in a response to this post), and arrived at the conclusion that I get the corner sharpness I want at f/5.6, not wider. (And I can use it with its lens hood). So, I have an all weather FF prime with excellent corner to corner sharpness (at f/5.6) on the K-1.

Great! But ....

D FA 28-105mm f/3.5-f/5.6

Where my K-1 is, this lovely lens is never far away. And I belatedly realised after doing the above tests that this lens can be used at 55mm and f/5.6. How does it compare with the DA* 55mm?

I added the 28-105mm lens to the same tests. And I think that, at f/5.6 and about 55mm, the 28-105mm is just about as good as the 55mm in the corners of the K-1's full frame. Close enough not to worry about it. And at f/8 it gets even better.

The 28-105mm lens weighs about 65 grams more than the 55mm lens. But I would typically be carrying it anyway. So it is the 55mm lens which would be "extra weight".

Obviously the 55mm lens is better in some respects in low light. But what respects? I'm pretty sure it will focus in situations where the 28-105mm lens won't. But the results would not be good unless I stopped it down to a value that the 28-105mm supports anyway.


When I'm outdoors, I prefer to carry a small amount of flexible kit, then make the most of it. So I prefer zooms to primes, with an obvious consequence in this case.

In the studio, I now have the D FA 24-70mm f/2.8. It weighs (very roughly) about twice as much as either of the above two lenses. But so what?

I think my DA* 55mm f/1.4 is about to be stored away until I can think of a use for it!

I've been coming to a similar conclusion for my DA* 300mm f/4. I really like having a 1-kilogram longish lens on the K-1. But if I remove its baffle, perhaps the 60-250mm will be that lens?

For me, zooms are taking over even more from primes!

. . . . .

K-5IIs plus DA* 55mm f/1.4

 Barry Pearson's gear list:Barry Pearson's gear list
Ricoh WG-6 Panasonic LX100 Ricoh GR III Pentax K-7 Pentax K-3 II +27 more
Pentax FA 28-105mm F3.5-5.6 Pentax K-1
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