28 or 35?

johnyates · 06-11-2013, 01:47 PM

Originally posted by EarlVonTapia

I wish Pentax made a DA 28.

That would be awesome!

Chris Mak · 06-11-2013, 02:22 PM

Originally posted by johnyates

That would be awesome!

It would!
I shoot the Cosina Zeiss lenses myself, and had the 35mm as my standard lens for a year or so, but eventually got the 28mm, and that focal length is really so useful on Apsc. The 28mm is now my standard walk-around lens. In my opinion it is a focal length that cannot be missed in the pentax prime-lens line.

Chris

**Kerrowdown** · 06-11-2013, 02:31 PM

I think you need to fed your LBA and get them both.

There's is also a school of thought you could actually sell the one you don't use so much later on. This is not something most folk here get into... selling lenses I mean.

strangeboy · 06-11-2013, 02:35 PM

Yeah... a DA 28, FTW!

Class A · 06-11-2013, 08:29 PM

Originally posted by audiobomber

I see what you mean though, the diagonal is right at 28mm.

Yes, it is ~28.84mm, so closer to 29mm, but 28mm is a standard focal length, whereas 29mm isn't.

Originally posted by audiobomber

I'm willing to extend normal status up to 40mm on the long end. Where would the short end be?

The angle of view (with respect to the image diagonal) of a perfect normal (~29mm) is 50.23°.
When you go up to 40mm, you are reducing the AOV by ~13°.
If you widen the AOV from the normal by the same amount, you get 22m.

Originally posted by audiobomber

Certainly 24mm is a wide angle. I'd have to call 25mm a wide angle too.

But then 40mm should be a "tele", shouldn't it?

Not sure it makes sense to allow more deviation towards the tele end compared to the wide end. In any event, the effect of a "normal" lens isn't that precisely defined in practice because viewing distances differ dramatically.

If you are viewing your images always from a distance that is equal to their diagonal then 28.8mm it is. If you have higher viewing distances than going higher with your focal length accordingly restores the "normal" (angle preserving) property. So I guess erring on the long side probably makes more sense in practice.

P.S.: I'm not sure why the Sigma 28/1.8 EX doesn't get more love on this forum. The few that have it like it a lot, as far as I can see. It is relatively big; maybe that's a detractor for many. However, IQ-wise and in terms of versatility it is excellent.

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06-11-2013, 01:47 PM	#16
johnyates Pentaxian Join Date: Aug 2011 Location: Saskatoon, SK Photos: Albums Posts: 1,345	Originally posted by EarlVonTapia I wish Pentax made a DA 28. That would be awesome!

06-11-2013, 02:22 PM	#17
Chris Mak Pentaxian Join Date: Jan 2013 Photos: Albums Posts: 639	Originally posted by johnyates That would be awesome! It would! I shoot the Cosina Zeiss lenses myself, and had the 35mm as my standard lens for a year or so, but eventually got the 28mm, and that focal length is really so useful on Apsc. The 28mm is now my standard walk-around lens. In my opinion it is a focal length that cannot be missed in the pentax prime-lens line. Chris

06-11-2013, 02:31 PM	#18
Kerrowdown PEG Moderator Join Date: Aug 2008 Location: Highlands of Scotland... "Hold Infinity in the palm of your hand" - William Blake Photos: Gallery Posts: 57,819	I think you need to fed your LBA and get them both. There's is also a school of thought you could actually sell the one you don't use so much later on. This is not something most folk here get into... selling lenses I mean.

06-11-2013, 02:35 PM	#19
strangeboy Senior Member Join Date: Nov 2011 Location: Chicago Posts: 126	Yeah... a DA 28, FTW!

06-11-2013, 08:29 PM	#20
Class A Pentaxian Join Date: Aug 2008 Location: Wellington, New Zealand Posts: 11,251	Originally posted by audiobomber I see what you mean though, the diagonal is right at 28mm. Yes, it is ~28.84mm, so closer to 29mm, but 28mm is a standard focal length, whereas 29mm isn't. Originally posted by audiobomber I'm willing to extend normal status up to 40mm on the long end. Where would the short end be? The angle of view (with respect to the image diagonal) of a perfect normal (~29mm) is 50.23°. When you go up to 40mm, you are reducing the AOV by ~13°. If you widen the AOV from the normal by the same amount, you get 22m. Originally posted by audiobomber Certainly 24mm is a wide angle. I'd have to call 25mm a wide angle too. But then 40mm should be a "tele", shouldn't it? Not sure it makes sense to allow more deviation towards the tele end compared to the wide end. In any event, the effect of a "normal" lens isn't that precisely defined in practice because viewing distances differ dramatically. If you are viewing your images always from a distance that is equal to their diagonal then 28.8mm it is. If you have higher viewing distances than going higher with your focal length accordingly restores the "normal" (angle preserving) property. So I guess erring on the long side probably makes more sense in practice. P.S.: I'm not sure why the Sigma 28/1.8 EX doesn't get more love on this forum. The few that have it like it a lot, as far as I can see. It is relatively big; maybe that's a detractor for many. However, IQ-wise and in terms of versatility it is excellent.