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04-29-2012, 02:44 AM   #1
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Sigma 30mm f/1.4 over FA 35/2 ? Advices?

Good day sirs,

I have been a Pentax and a K5 user since one month, and I am currently using the FA 35/2 as a normal wide. Or whatever. Honestly I like the lens, I like its neutral colors and tack sharpness. The only issue I get with this lens is focusing errors happening more frequently than expected.

Cutting it, I have a chance to sell the FA to a friend and get the Sigma 30mm 1.4 for a not so much price difference (around $90 from my pocket). But I am a little hesitant to use a 3rd party lens after so short a time since coming to Pentax, and also I am not sure if the Sigma's lack of sharpness in the corners will bother me since I use the FA in some city/landscape shots too and I am fairly happy with its performance.

I will probably use the sigma in f/1.8 or smaller for better sharpness, so I think the difference in aperture will not matter much.

But I can't ignore the differences in bokeh, probably better focusing and 5mm wider fov. Or should I ?

Really stuck here without a decision, I could use a little advice

Thank you.

04-29-2012, 03:31 AM   #2
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FWIW the Sigma 30mm is plenty sharp in the corners,
Wide open-
04-29-2012, 03:37 AM   #3
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@TOUGEFC not a whole advice but thank you for pointing out that your lens is sharp in the corner.

your beautiful 3d images are shot with this lens?
04-29-2012, 03:38 AM   #4
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Others here know better than I, but I'm guessing the focusing issues are a camera issue more than a lens issue.
And, personally, I'd ALWAYS take a Pentax prime over aftermarket.

04-29-2012, 03:47 AM   #5
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Hi,

First off, on the K5 the 35mm is not wide at all, it's normal. However, if you are happy with it no problem. Secondly, it seems odd that you are having focussing problems with it. Do you get this with your other lenses?

If you are concerned about shaving off mm I would suggest that you look at something different altogether - perhaps a 15 or 21mm limited lens. I would keep the FA 35mm if you enjoy using it though. Have you tried compensating for focusing problems using the lens adjustment feature in the K5?

Jez
04-29-2012, 03:49 AM   #6
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A lot depends on what you want to do with it. The FA 35 is a very nice lens and so is the Sigma 30. To me, the Sigma is best used for portraiture, although stopped down, it can do OK with other things. The biggest thing that bothered me about the Sigma was that the bokeh could get a little rough at times. It's actually nicest wide open, from that standpoint. I do think the Sigma is usable at f1.4, depending on what you are shooting..

04-29-2012, 04:21 AM   #7
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thanks for quick replies.

when the lens focuses, it's dead on and tack sharp even at f/2 (a reason making me hesitate to sell the lens), but when it can't find the focus, it simple can't find it, or focuses ashtray.

the focusing problems are not in the character of back or front focusing, it just seems like the lens can't find the focus. I deleted many photos because of this, but here are some I could find:

here the cases of oranges, but no focus whatsoever;





here the wings of the butterfly, but focused the lights behind;



here the person herself, but no focus anyway (middle of face intentionally blurred over request);




here focus on the back of the cat, but no focus;




the intention was to focus on the paw between my fingers, but hunted so much and completely missed the focus;




---------------------------------------------

I don't have any problems focusing in the 85 FA*, didn't have focusing problems in the 18-55 AL II. None that I could spot anyway. @jeztastic I thought of the 21mm, but f/3.2 is not to my taste

I am generally using the FA 35 for street candids and indoor portraits, and a some for interesting urban items/landscapes.

Last edited by Crosshair; 04-29-2012 at 04:28 AM. Reason: addition
04-29-2012, 06:22 AM   #8
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It seems the lights are in focus in the butterfly picture, and the ears of the cat are in focus rather than its back. It's a little hard to tell for sure from the lower-than-original-resolution postings, but if I am right, then maybe those were an issue with where your camera chose its focus point. Through some focus chart testing, I've found my K-5 focus points are not centered over each of the indicated red LED focus points in the viewfinder, they are shifted a little.

Also, I've found that the camera does a poor job of focusing on moving subjects, maybe that explains the hunting you mentioned in the cat paw picture.

Also in your custom menus, options #15 and #16 are normally set to focus priority. But if set to release or FPS priority, the camera will fire the shutter as soon as you full press the shutter button, even before it has obtained focus. Make sure these are set to "1" for focus priority.

04-29-2012, 07:08 AM   #9
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A couple of features you might miss if you switch from FA35 to Sigma 30:

The FA35 is tiny compared to the Sigma.
The FA35 takes 49mm filters like a lot of other Pentax primes.
The FA35 focus ring rotates in the usual Pentax direction, the Sigma is backwards.
The FA35 has an aperture ring - great for reversal rings, stacking for macros etc.
The FA35 has "Pentax colours" whatever that is. I have a FA35 and I can't really tell.

Regards,
--Anders.
04-29-2012, 07:22 AM   #10
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@Tanzer thank you. I always choose my AF points and go for single focus point. I guess this worsens the situation. And the #15 and #16 are as it came, both set to 1. maybe the centering of red leds as you mentioned. I might do a similar test. I am disappointed at your comment on moving things, but that might also be the case. I don't know. But here are a couple of objections to it, which I shot with the 85 myself









At first I was astounded by the 3-d look of Sigma images, but now I don't know. Too early. I will probably wait some more time as I am fairly new to Pentax and learn to get used to my gear. Seems the right choice not to leave an original equipment after a short time 85 is a keeper but the future of this 35 I am not sure about. Just gonna take some time with it.

@asp1980 I too heard this "Pentax colors" too but I think those are more prevalent in the 50mm's, especially in M and A. I can distinguish them a bit too now, but only when I see them. Can't really exactly tell how's the pentax green, how's the pentax red etc.
04-29-2012, 07:46 AM   #11
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The FA has nicer bokeh than the Sigma IMO. The Sigma excels at fairly close up portraits where the background is totally OOF, but where the background is only semi-out of focus, the bokeh can be jittery and highlights get progressively more triangular / tick shaped toward the corners. In the sigma's favour, 30mm is noticeably wider though!
04-29-2012, 07:47 AM   #12
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I think there's a big difference between the pictures you've posted. The one's where the focus is missed, there's a lot going on, there's a lot for the camera to focus on - particularly where you are holding the cat! However, the pictures of the birds - the camera has two choices, the birds or infinity... It may just be that at 35mm the camera has to work a lot harder at picking the right spot.

Another thing to try might be setting the AF button to cancel AF. That way, you focus, check, hit AF, recompose.

Of course you might be right, there may be a problem with the lens, but best to try some different techniques to be sure.

For me the Pentax colours are saturated blues and muted reds, I've found this particularly with 'M' lenses.
04-29-2012, 11:09 AM   #13
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I think your issue is with the size of Pentax's auto focus points. It becomes more pronounced with wider angles. Zoomed at 85mm or 100mm, the camera will seldom miss, but at wider angles, the camera will choose the most contrasty item in the auto focus point area (quite large). At 16mm, it is really frequent that my K5 focuses on the background rather than on what I want.

Anyway, I don't think the Sigma would do any better than the FA 35 in that respect.
04-29-2012, 11:29 AM   #14
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thank you all for the ideas, these quite useful for me, especially @Rondec your comment about AF point area size. maybe it is something I need to get used to after Nikon. but it's simply frustrating. And it's interesting that 85, which is supposed to focus slower than 35, is superior to 35 in this regard, as @jeztastic pointed out.
04-29-2012, 11:46 AM   #15
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I know now that my K-5 center AF point is in the lower right of the confirmation square. I lost a few images learning just where the center point resides, especially macros. You might go to AF-C and wander around the center point, to see just where the sweet spot is. I have yet to try this with others, perhaps all are offset the same..
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