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08-16-2012, 09:05 PM   #91
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My initial impression from the photo in the review is that the Sigma is significantly bigger than the Pentax, but it's actually the lens hood on the Sigma that makes it look so much larger. Is the hood on the 31mm tiny because it was designed as a wide-angle lens for full frame?

08-16-2012, 09:52 PM   #92
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QuoteOriginally posted by Edgar_in_Indy Quote
My initial impression from the photo in the review is that the Sigma is significantly bigger than the Pentax, but it's actually the lens hood on the Sigma that makes it look so much larger. Is the hood on the 31mm tiny because it was designed as a wide-angle lens for full frame?
I believe a bigger hood would lead to vignetting on the FA31mm on FF.
08-16-2012, 11:33 PM   #93
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QuoteOriginally posted by Digitalis Quote
Niether lens is supposed to be a pancake lens (30mm f/1.4\FA31) and IMO it is a tad unfair to compare them to smaller, slower lenses - because I have yet to come across a pancake lens as fast as f/1.4. Fast lenses are always going to be big and heavy, when compared to slower lenses. Unless you are shooting Leica, or other mirrorless cameras for instance: The Voigtlander 35mm f/1.2 is one stop faster and slightly smaller than the FA31.
But manual focus, so no drive mechanism for the screw drive.
08-17-2012, 03:23 AM   #94
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QuoteOriginally posted by snake Quote
But manual focus, so no drive mechanism for the screw drive.
When you are using a lens designed for manual focus, it isn't as much of a hinderance when it comes to producing excellent work.

08-17-2012, 04:40 AM   #95
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QuoteOriginally posted by Digitalis Quote
When you are using a lens designed for manual focus, it isn't as much of a hinderance when it comes to producing excellent work.
Never said it was. The quote I was citing was referencing size, not AF vs MF.. The drive mechanisms for AF, even screwdrive, require room, so it's tough to compare a lens for size, saying the aperture is larger, yet smaller than an AF lens with a smaller aperture.

Incidentally, one of my most-used lenses is an M85 F2.
08-17-2012, 06:05 AM   #96
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QuoteOriginally posted by gtl Quote
I believe a bigger hood would lead to vignetting on the FA31mm on FF.
The odd thing about the hood on the 31 is I've seen it mounted on a Canon 5D, where it ends up rotated about 45 degrees. You would think that this would cause vignetting, but it doesn't. This tells me that the hood could have been bigger. I guess the designers didn't think it needed to be.
08-17-2012, 06:48 AM   #97
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QuoteOriginally posted by Designosophy Quote
The odd thing about the hood on the 31 is I've seen it mounted on a Canon 5D, where it ends up rotated about 45 degrees. You would think that this would cause vignetting, but it doesn't. This tells me that the hood could have been bigger. I guess the designers didn't think it needed to be.
Yeah. I saw the images on Flicker from a guy with a Canon 5DII using a modified 31mm LTD. Because of the differences in mount, the lens is rotated 45 degrees clockwise (when looking at it from the front). I have been looking at ways to attache a larger hood for both protection and flare. There are a couple of good ideas out there for a slightly longer hood.
08-17-2012, 09:05 AM   #98
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Hmm.... I dunno if this helps, but i kind of did a "rough" estimation on a rather simple concept, FL x1.5 crop factor = "proper" hood without vignetting.

I.e:
On FF - 28mm FL would require ~28mm/2.8cm deep for the hood before vignetting happens.
On APSC - 28mm FL would require ~42mm/4.2cm deep

How i knew, i've tested using a generic telephoto hood 40mm/4cm deep on my A28/2.8.
I've also tried, by stacking multiple generic 20mm/2cm deep "standard" hood making a 60mm/6cm deep hood, on my A50/1.4 without any vignetting.

Therefore, the FA31 would be able to use a ~46.5mm/4.6cm deep hood without vignetting. The original hood length helps but could potentially handle more with a longer one.

Take into consideration the DA*55, if i'm not wrong, take off its hood and shoot FF, and there'll be no vignetting but put it on and there will be vignetting. For this lens, it is all in the hood because 55mm x 1.5 = 82.5mm/8.2cm, therefore technically speaking, you can utilise an 80mm/8cm deep hood without vignetting on APSC. *Ok... NOT sexy.. But you get the idea... :P *

Another tip to note: Round down the final length after calculation for safety measures..
Go try..

PS: In the end, i just reverted back to a standard 20mm/2cm deep hood but a telephoto 40mm/4cm hood, on my A28 and A50 respectively, because it looks stupid and long... Hahaha!

08-17-2012, 09:22 AM   #99
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Good thing Pentax has no FF

...yet.
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