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07-24-2012, 04:51 AM   #1
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FA31mm F1.8. or Siggy 30mm F1.4

I need a fast normal lens which is sharp wide-open across the frame. The lens will serve me for architectural photography and interior photography.
I have also in mind FA43 for my K-5, what do you think?

07-24-2012, 05:05 AM   #2
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I find 35 to be a bit tight in many instances for interior photographs. I can't imagine that 30 or 31 will open it up too much. What about the 21 instead? On the K-5 the difference in f should not be a huge factor.
07-24-2012, 05:15 AM   #3
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The FA31 would definitely be better if you need edge to edge sharpness. The Sigma 30 is better as a portrait lens, where the center is sharp, but borders get kind of soft, but don't matter so much in the final photo.
07-24-2012, 05:24 AM   #4
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I'm with the "31 isn't wide enough for interior photography" crowd. A 31 isn't much different from a standard lens on APS-c. With so many options in the 16-50 and 10-24 range, why wouldn't you be looking at a fast zoom?

07-24-2012, 05:27 AM   #5
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FA31 is sharp across the frame. So is a DA12-24.
07-24-2012, 07:14 AM   #6
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@normhead, @Docrwm: When I examine my photos, you're right, most of them
are less than 30mm with F5.6 or greater. I have already Tamron 17-50mm/F2.8.
With this one, I'd most of time ISO 1600 to 6400 at 1/6 - 1/15th second speed.
I saw photos taken with FA24mm F2, they are wonderfull. Unfortunately the
production of the lens is stopped already. I will looking for 21mm F3.2, if it is
sharp wide-open with longthrow DOF.

@Rondec,@twitch: Is it really FA31 sharper across the frame than Shaggy 30mm F1.4? The problem is, I can't
return the item I buy. There is no such policy in our country. So, I have to decide, go buy and pray
that my decision is right. Or re-sale the new lens as second in perfect condition.
07-24-2012, 07:33 AM   #7
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QuoteOriginally posted by purwoadi Quote
I need a fast normal lens which is sharp wide-open across the frame. The lens will serve me for architectural photography and interior photography.
I have also in mind FA43 for my K-5, what do you think?
Are you shooting film or digital? The FA 31 is without equal, but it's only a normal lens on APS-C, I would think for architecture you'd want something more like the FA 20. But then you know what you are shooting, I don't. The FA 43 is nice, and not too expensive, but it's getting a little towards the telephoto side.
07-24-2012, 08:28 AM   #8
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For architectural shots, particularly indoors, I cannot recommend the Sigma 30 f/1.4. It is a fantastic short portrait lens, sharp as can be in the center, and it has great contrast, but I used it for some landscape shots and even stopped down to f/5.6, it is soft at the edges. At f/11, it is much better, but at the very corners, some softness persists. But indoors, at wide angles and large apertures, you're going to have trouble getting everything in focus. I'd suggest a tripod and longer exposures at higher f-stops for indoor architecture.

Edit: Here are a couple indoor shots with the Sigma 30. The first is at f/1.8, the second at f/1.4. I don't have full resolution on Flickr, but it is fairly high if you go to the image on Flickr, right-click and select "original." They're urbex shots, so please don't mind the mess:








Last edited by Designosophy; 07-24-2012 at 08:45 PM.
07-24-2012, 08:40 AM   #9
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Another option would be the hugely popular sigma 10~20, that would give you pretty good IQ plus the focal you need with flexibility for interior shots. Also, as Twitch noted, the pentax 12~24 is a great option...
07-24-2012, 08:52 AM - 1 Like   #10
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I highly recommend the Pentax DA 12-24 which I have used extensively for tight interior fashion shoots. Very little distortion and sharp from wide open:
Attached Images
 

Last edited by Parallax; 07-24-2012 at 02:18 PM.
07-24-2012, 09:20 AM   #11
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I love the Sigma 30/1.4 .. but not for your intended use where the 31 Ltd would be better, but is still the wrong lens for the job.

I take a lot of interior shots (1,000s per year) and use a Sigma 10-20 (and virtually 95% are at 10mm), tried the 15 Ltd a few times but it is far too narrow. Either one of the UWA zooms from Sigma, Tamron (both 2mm wider than the Pentax - which is 20% more coverage) or maybe the Sigma 8-16, would be better for home interiors. I'm even thinking of swopping out my 10-20 for an 8-16 just for that extra 2mm.
07-24-2012, 10:37 AM   #12
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QuoteOriginally posted by Frogfish Quote
I love the Sigma 30/1.4 .. but not for your intended use where the 31 Ltd would be better, but is still the wrong lens for the job.

I take a lot of interior shots (1,000s per year) and use a Sigma 10-20 (and virtually 95% are at 10mm), tried the 15 Ltd a few times but it is far too narrow. Either one of the UWA zooms from Sigma, Tamron (both 2mm wider than the Pentax - which is 20% more coverage) or maybe the Sigma 8-16, would be better for home interiors. I'm even thinking of swopping out my 10-20 for an 8-16 just for that extra 2mm.
Any idea what the degree difference is in the field of view between 8mm on the Pentax and 10 on the Sigma or Tamron would be?

Also the 5-way comparison on the UWA Zooms is a great place to get up to speed on these options.
https://www.pentaxforums.com/reviews/sigma-10-20-comparative-review/the-bottom-line.html
07-24-2012, 10:53 AM   #13
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QuoteOriginally posted by Docrwm Quote
Any idea what the degree difference is in the field of view between 8mm on the Pentax and 10 on the Sigma or Tamron would be?
20%...?
07-24-2012, 02:18 PM - 2 Likes   #14
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QuoteOriginally posted by Docrwm Quote
Any idea what the degree difference is in the field of view between 8mm on the Pentax and 10 on the Sigma or Tamron would be?

Also the 5-way comparison on the UWA Zooms is a great place to get up to speed on these options.
Sigma 10-20mm F3.5 vs F4.0-5.6 - The Bottom Line - PentaxForums.com
Doc.

Relative FoV (horizontal) on x1.5 multiplier crop sensor :

8mm = 112.6 degrees
10mm = 100.4 degrees
12mm = 90 degrees
15mm = 77.3 degrees
16mm = 73.7 degrees
17mm = 70.4 degrees
20mm = 61.9 degrees
24mm = 53.1 degrees

Rounded.

Sigma 10-20 = 100 to 62 degrees
Tamron 10-24 = 100 to 53 degrees
Sigma 8-16 = 113 to 74 degrees (n.b. the differing angles given by Sigma are correct for the x1.7 Foveon sensor)
Pentax 12-24 = 90 to 53 degrees

So the 8mm to 10mm difference is 12.2 degrees (horizontal).
07-24-2012, 02:32 PM   #15
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QuoteOriginally posted by Frogfish Quote
Doc.

Relative FoV (horizontal) on x1.5 multiplier crop sensor :

8mm = 112.6 degrees
10mm = 100.4 degrees
12mm = 90 degrees
15mm = 77.3 degrees
16mm = 73.7 degrees
17mm = 70.4 degrees
20mm = 61.9 degrees
24mm = 53.1 degrees

Rounded.

Sigma 10-20 = 100 to 62 degrees
Tamron 10-24 = 100 to 53 degrees
Sigma 8-16 = 113 to 74 degrees (n.b. the differing angles given by Sigma are correct for the x1.7 Foveon sensor)
Pentax 12-24 = 90 to 53 degrees

So the 8mm to 10mm difference is 12.2 degrees (horizontal).
Thank you Sir, you are a mensch! Too laze (was at work so that is my excuse) to find it for myself. +1 for the assist!

I remember some of that from when I researched purchasing the Tamron 10-24 18 months ago. I recall that the FoV was very nice on paper, and it has proven to be in practice as well, for the Tamron. I can see how the 12.2 degrees of difference could be very useful in tight spaces or creatively between the 10mm and 8mm lenses too.
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