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01-02-2010, 10:00 PM   #1
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Advice sought on 31 Limited issues

Hi all:

I have posted before about the 31 Limited I was considering buying--and then the 31 Limited I actually bought!!

I purchased the 31 to provide me with a low light lens, and also a back-up to my 16-50, which had been at Pentax for repair for quite some time.

I know I have not posted any pictures, but having said that, here are my issues for which i was seeking advice.

The 31 Limited, shooting RAW, appears largely indistinguishable from my 16-50. At 2.8 the 16-50 basically matches the 31 Limited at 2.8 and of course as the f stop gets higher in number the images are virtually identical, though perhaps very serious pixel peeping might show some difference--but I really have seen none. In fact the images at all the same f/stops look the same.
The 16-50 at 2.8 also seems to match the 31 Limited down to 1.8.

I know another member indicated this may simply show how good the 16-50 is. Am I missing something? I spent many years using high end telescope optics, so I feel I am able to fairly assess different optics and recognize the difference between very good optics and great optics often is rather nuanced.

I would hate to think I received a mediocre copy of a nearly $1k prime lens.

The 31 is not bad and I do not see any flaws, other than some limited difficulty focusing in lower light. So, the lens does not appear to be of poor quality, just nothing better than the 16-50.

Any thoughts would be greatly appreciated.

Gregg

01-02-2010, 10:05 PM   #2
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Have you peeked at the borders and extremes? FA 31 should perform much better there. Also, FA 31 has very low lateral chromatic aberrations.
01-02-2010, 10:07 PM   #3
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Gregg I have both, and both of mine are good copies.

In this regard I've never been able to fault either lens thus far (other than the 16-50's occasional focus hunt. As for comparing the two, I haven't scrutinised results between the lenses so cannot say, but it's easy for me to say both lenses are worth the money one has to pay for them.

You'll be hard-pressed finding a lens giving better results than these two.
01-02-2010, 10:29 PM   #4
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Hi ASDF and Ash

ASDF and Ash:

Thanx so much for the replies. At the risk of sounding totally green--what is the point in having such an expensive lens (the 31) if it really is no better than the 16-50? Weight and size? If there is a difference at the edges I do not see it and I just took some pictures of my dog to see if I could see any appreciable difference. The fact that I had to go back and forth between the pictures over and over is telling.

I did try the Sigma 24 and was disappointed. Not a poor lens, but not a great one. I also tried the 18-55 WR as an inexpensive back up. About the same as the 24--not poor, only ok.

Anyway, I am just disappointed and was hoping I was missing something.

Thanx so much again for the quick replies.

Gregg

01-02-2010, 10:34 PM   #5
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I think you may be missing something. Just saying "The 16-50 at 2.8 also seems to match the 31 Limited down to 1.8." worries me. There's going to be a significant difference in the images between a lens that starts at f/1.8 wide-open, and one that starts at f/2.8 wide-open.

Not to impinge on your optical judgement, but there is a world of difference in spotting problems with a telescope optic where you view the image constantly in full motion, and a camera optic where you capture a scene into a still image. Camera optics are almost always of higher quality than comparably-priced telescope optics, because flaws are much easier to spot in a still image, especially one blown up so large as on modern multi-megapixel sensors.

This isn't to say that both lenses don't perform similarly. I haven't used the 31 ltd, but I have used the 16-50 and to think it produces similar images to the ltd at f/2.8 is not a far stretch of the imagination. But all of this conjecture is useless without posting images so that additional trained eyes can see if there is merit to your claim.
01-02-2010, 10:43 PM   #6
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QuoteOriginally posted by lawjbm Quote
ASDF and Ash:

Thanx so much for the replies. At the risk of sounding totally green--what is the point in having such an expensive lens (the 31) if it really is no better than the 16-50? Weight and size? If there is a difference at the edges I do not see it and I just took some pictures of my dog to see if I could see any appreciable difference.
FA 31 works on film cameras and on the mythological FF Pentax DSLR.

I'm not sure whether DA* 16-50 f/2.8 at around 31mm is FF compatible.

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/31629-da-lens-...ts-thread.html

Also, FA 31 is great for taking shots of ISO resolution test charts.

EDIT: wallyb makes a valid point. Compare at the same aperture.
01-02-2010, 10:48 PM   #7
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Yes, the 31 ltd is indeed sharp wide open, which automatically makes it more versatile than the 16-50, having apertures of f/1.8-2.8 to your disposal.

Nevertheless, Wally's point is valid and if you are truly concerned about the results, you will do well to post examples at resolutions that reflect your perceived similarities in the corners and edges.
01-03-2010, 12:14 AM   #8
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QuoteOriginally posted by lawjbm Quote
Hi all:

I have posted before about the 31 Limited I was considering buying--and then the 31 Limited I actually bought!!

I purchased the 31 to provide me with a low light lens, and also a back-up to my 16-50, which had been at Pentax for repair for quite some time.

I know I have not posted any pictures, but having said that, here are my issues for which i was seeking advice.

The 31 Limited, shooting RAW, appears largely indistinguishable from my 16-50. At 2.8 the 16-50 basically matches the 31 Limited at 2.8 and of course as the f stop gets higher in number the images are virtually identical, though perhaps very serious pixel peeping might show some difference--but I really have seen none. In fact the images at all the same f/stops look the same.
The 16-50 at 2.8 also seems to match the 31 Limited down to 1.8.

I know another member indicated this may simply show how good the 16-50 is. Am I missing something? I spent many years using high end telescope optics, so I feel I am able to fairly assess different optics and recognize the difference between very good optics and great optics often is rather nuanced.

I would hate to think I received a mediocre copy of a nearly $1k prime lens.

The 31 is not bad and I do not see any flaws, other than some limited difficulty focusing in lower light. So, the lens does not appear to be of poor quality, just nothing better than the 16-50.

Any thoughts would be greatly appreciated.

Gregg

hi Gregg, you seem very much unsatisfied with the FA31.
do you mind selling it to me for $100 bucks?

01-03-2010, 12:50 AM   #9
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Hi all

Thanx again for all of your replies.

I am up late here (about 2:30 a.m. here in Maine, USA). I will take some more pictures tomorrow and post them.

It may very well be that there is some perceivable difference, but if so, I cannot see it so far and all I do is pixel peep in Photoshop with my photo restoration and in fixing my shoots (unfortunately, I am better at CS4 than photography, and I am not exactly great at CS4).

I will shoot RAW, do the same limited post on both and please let me know if I am off base.

Thank you all again.

Gregg
01-03-2010, 12:55 AM   #10
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Your subject matter will also influence what you are seeing. If the subjects are simple without a lot of detail, you are not really pushing either lens. Try something like a cityscape with lots of windows and stuff that will really test the lenses, then you might start seeing differences when you pixel peep.
01-03-2010, 01:39 AM   #11
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Check out how the limited prime renders at 2-3 meters and F1.8 - F2. The shots have volume to them!

I dont have the 16-50 zoom, but I havent seen this effect from others pics either.

And yes, check out corner performance wide open.
01-03-2010, 01:53 AM   #12
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QuoteOriginally posted by ilya80 Quote
Check out how the limited prime renders at 2-3 meters and F1.8 - F2. The shots have volume to them!

I dont have the 16-50 zoom, but I havent seen this effect from others pics either.

And yes, check out corner performance wide open.
what's a meter?


Don't mind me...up because tonight the pain meds are bouncing like water off a ducks back. so I am sorta goofy from the extra doses.
01-03-2010, 02:01 AM   #13
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Hi Gregg,
As the 31mm Limited is famous for being sharp even at f/1.8 it should be much better than the DA* 16-50mm at f/2.8.
My advice to you is to find someone in your area who has the 31mm Made in Japan and do a comparison test to see if you have a bad copy.
I've never seen or heard a complain from someone who owns the FA 31mm Limited that is Made in Japan, but I had experienced two 31mm Limited lenses Assembled in Vietnam and they were both substandard to say the least. And I believe there are other people as well who bought the Vietnam version and question it's quality.
Just to show you the difference I found between the lenses see the full size images bellow:
Both shots are focused just under the "NO SMOKING" sign and both are shot at f/1.8.
Made in Japan:
http://farm3.static.flickr.com/2719/4162868642_ac89ebf3f0_o.jpg
Assembled in Vietnam:
http://farm3.static.flickr.com/2691/4162111759_4cbc1ccea7_o.jpg
The problem is definitely not a back or front focusing, to me it looks more like decentered lens.
01-03-2010, 02:15 AM   #14
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QuoteOriginally posted by Voe Quote
Hi Gregg,
As the 31mm Limited is famous for being sharp even at f/1.8 it should be much better than the DA* 16-50mm at f/2.8.
Nope. DA* 16-50 is sharper *in the center* at f/2.8 than DA 31mm is at f/1.8 (the unfair comparison the original poster made).

Pentax SMC DA* 16-50mm f/2.8 ED [IF] SDM - Review / Test Report
Pentax SMC-FA 31mm f/1.8 AL Limited - Review / Test Report

Last edited by asdf; 01-03-2010 at 02:24 AM.
01-03-2010, 02:37 AM   #15
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QuoteOriginally posted by asdf Quote
Nope. DA* 16-50 is sharper *in the center* at f/2.8 than DA 31mm is at f/1.8 (the unfair comparison the original poster made).
1. Of course, I meant both lenses at f/2.8.
2. Mind you the original poster didn't mention anything about *in the center*.
3. The OP also said the following: "The 31 Limited, shooting RAW, appears largely indistinguishable from my 16-50. At 2.8 the 16-50 basically matches the 31 Limited at 2.8" ...

4. Since you are pointing me the Photozone tests you might as well see how both lenses compare at f/2.8. Of course it's an unfair comparison because the 31mm Limited is stopped down (being an f/1.8 lens) but you get the point of the performance of the 31mm Limited at f/2.8.
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