[jezza323]

the Sigma 30mm f1.4 is not the sharpest lens around, and has a bit of distortion too, but the images it produces care not for the technical aspects. It really hits the mark well IMO

Whole thread of Sigma 30mm love - https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/149865-sigma-3...-examples.html

And my Sigma 30mm shots on Flickr - Sigma 30mm f1.4 - a set on Flickr


I can also comment on the Tamron 17-50mm. Its great, sharp, fast and all that, but as per - https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/174733-sell-my...mm-f2-8-a.html

I almost always pick the Sigma 30mm or Sigma 10-20mm over it

[eddie1960]

Thanks for that Eddie, now where's my photo of the Ryerson Quad?

.

HAHA forgot that, ok i haven't been walking home lately so haven't passed it

i'll throw a 14 or 21 on the camera and walk home in the next week or so (too bad i didn't bring the camera today it's a beautiful afternoon)

if you go to aden of course you could just walk across the street with your new FA 31 and take one yourself

[normhead]

I've been looking at numbers all after noon..

Here are comparison charts for these lenses form the Lens Data base



Here are the numbers from The three lenses I ended up most interested in. The others not included the Sigma 30 and the Tammy 17-50 , photozone tests showed great center sharpness, but poor border sharpness, which to me would suggest good portrait lenses, not so good for landscape. I included the DA 35 macro... but it's not in the class of the other 2 according to photozone numbers. The numbers are not directly comparable between the Pentaxes and the Sigma... but where the numbers are on the graph is helpful.



So that leaves me with the Sigma 17-50 looking about the same at 31mm with the Sigma having more range. Has anyone used both of those lenses?

[JinDesu]

One slight issue with comparing MTF charts on photozone is that it appears the Sigma chart going to 2600 lines is on a different camera than the 31 limited. That can skew some comparisons.

I like to use (disregard the long link) to compare charts of lenses as long as they are shot with the same camera. Sigma 17-50mm f/2.8 EX DC OS HSM Lens Image Quality

From what I can see between the Tamron 17-50 and the Sigma 17-50, the Sigma is slightly better at the center, while the Tamron is better at the corners. This is at F8 and 17mm and 35mm. It contradicts the Photozone data you presented a bit.

*edit*
Oh cool, it summarizes the link for me.

[normhead]

I compared the lenses as close as I could to 31 mm so that may be the issue with the zooms. It looks to me like at f8 and 35mm the Sigma has both more contrast and is a bit sharper in the corners, not that the site is working in a way that I have a clue if it's doing what I think it's doing. Thanks for the link by the way. A little bit of a colour chart would be nice.

I forgot to post the photozone stuff for the DA*16-50. It basically said excellent at 16mm but it fell off a bit by 24mm and even more by 50mmm.

[JinDesu]

Erf, if we're talking about the Digital Pictures site that I just linked, there is no way the Sigma at F8 is better in the corners than the Tamron.

[normhead]

Oh, OK , now I get it......back to ....where ever.

[JinDesu]

What I was trying to say is to try to use online resources to compare the lenses is going to be really difficult, a lot of them don't do very well at keeping the camera the same between tests of different lenses, and it all gets confusing. For example, I used that chart site for lenses between Sigma and Tamron, but it does nothing for me in comparing to Pentax. I have a few other sites where they tested several Pentax lenses between each other, but it doesn't help me to compare to Tamron and Sigma. Photozone has some lenses that can be directly compared, but they don't really make it clear which (and their disclaimer says not to compare at all). At best, I read their summaries to see if they make any true comparisons (same with lenstip).

My gut feeling says there is no way the Sigma 17-50 is sharper or renders better than the 31 limited or the 35 macro - as good as the Sigma is. However, it gives more reach, is better than the kit lens and even the 16-45 by a bit (although I guess that's debatable), is quiet, and looks sexy.

And sometimes it just comes down to biting the bullet and hoping for the best. That's where I stand with my Tamron 70-200. Maybe all the resources I used were wrong and the Sigma or the Pentax FA*80-200 is better, but hell - it's a damn good lens.

[normhead]

Now you have my attention, because after we fill the gap at 35mm the Tammy 70-200 2.8 is next.... there are so many problems with the on-line tests, they may have gotten a good copy of one lens and a bad one of the other. I like lenses that test well on the forum here, the Sigma is rated at 9.5 for sharpness, way above any other lens I looked at except the DA 35 macro, and it's rated above the 31 ltd.... the weakness of the SIgma 17-50 according to Pentax users is its autofocus. But only 4 Pentax users have filed reports. I think it's possibly going to come down to the F.1.8 vs. F2.8. The 31 hits maximum resolution at F4. That's not so good for an landscape lens. I woul dhave preferred at least 5.6.

I also discard lenses rated under 9 overall on the forum. The DA 35 macro is rated almost as high as the 31 ltd on the forum...practically identical.
So far nothing is as center sharp as the Sigma 17-50, and 31 ltd at their highest ratings. The 31 has the widest aperture and the least fall off of sharpness from centre to border, until F8

After one day of poking around it still looks like the lens to beat.

I'm still a little suspicious about how the 35 macro looks so good on the forum rating and so crummy on the MTF charts.

[Frogfish]

The 31 hits maximum resolution at F4. That's not so good for an landscape lens. I would have preferred at least 5.6.

Why ? The 31mm is considered a fantastic landscape lens. You can always use hyperfocal distancing and for the 31mm at f4 (on APS-C) that means from 11.4m to infinity (though actual DoF would range from 8m to infinity). Though optimal sharpness will be ca. 25m to infinity (f5.6 would give you 12m to infinity and f8 just under 6m to infinity.

I also discard lenses rated under 9 overall on the forum. The DA 35 macro is rated almost as high as the 31 ltd on the forum...practically identical.

You really have to be careful in using the overall ratings in the PF forum. Some people are stepping up from crummy lenses and almost any decent lens would look good to them and of course the ratings are totally subjective and usually not rated against better lenses but against what the reviewer own lenses. Catch someone in a bad mood and a lens is rated down, catch them just after getting laid and everything gets a 10 !

[jezza323]

Personally I wouldnt call anything 30mm or more a "wide angle" on APS-C anyway, but then I do love my 10mm :P

[normhead]

Catch someone in a bad mood and a lens is rated down, catch them just after getting laid and everything gets a 10 !

My method of using the forum ratings is 1. don't look at anything with less than 25 posts... 2. Take the score minus 5 , no one rates anything under 5 anyway. If you look at at 8 out of 10 as 3 out of 5, it makes a lot more sense. It's really irritating when there are 3 posts and everything is a 10. Especially when you look at MTF chard, croma charts and distortion charts and perfect scores are very rare. In fact on the photozone 10mp MTF charts there are probably 5 lenses that have a 2350 score at any Fstop and even they have one "perfect score" out of 5 listed f-stops. Regardless of everyone saying you can't trust those scores, at least the guy did something. He had access to all the lenses he tested. He made up some kind of criteria and he applied it equally to each lens he had. So you really can't say the scores mean nothing. If you look at the hundreds or thousands of each lens produced, you also have to realize that if he tested one, there's a pretty good chance theone you get may not test the same as the one he had. The are a bit of evidence to use in your search. However I disagree that you can't look at test scores and user ratings and make yourself a list. The world I did on the DA*60-250 and Tammy 90 macro got me two very good lenses.

Whether or not you can go further than look for a lens that people like to use with an MTF sweet spot I don't know? And Idon't know what you can do about that. I tried a Sigma 120-400 in the store and it looked like everything I wanted. I got it home and it was soft in the long end. Sometimes it takes getting out in real shooting conditions to decide. That's where my lack of ability to rent Pentax equipment really hurts.

Anyway....the 31 is still the leader, based on reputation and it's performance on photozone's MTF charts, where the lens manages to keep it's center and borders in excellent range over 3 f-stops with one near perfect score. Re-cjecking the numbers on the Sigma 17-50 I can see the edge softness discussed above... the Tamron's center highs are in teh excellent range, but not as high as the Sigma.'s but the Sigma has no borders in the excellent range.

So here's what I've decided so far... 31 ltd... best overall quality and real sweet spot and excellent borders (hard to find)...but pricey.
Tammy 17-50 Excellent over an unbelieveable range if you're used to looking at these score, both excellent centres and excellent borders, but no real sweet spot ...best bang per buck by a wide margin.
Sigma 17-50 sweet spot but way too much fall off on the borders, very few borders in excellent range.
Pentax DA* 17-50 excellent center scores huge fall off borders and edges, no excellent borders anywhere in it range.. 16 mm centre sweet spot weak at 50mm...WR
Pentax DA 35 macro very sharp centers but no borders in the excellent range, the centre sweet spot is incredible from f 3.2 to F8 not falling out of the excellent range until f-11 and still very close.

Because of their borders, you have to put the SIgma and DA* and DA 35 macro into more of a portrait or studio setting than landscape where you want excellent across the whole image.

So that leaves me with the 31 and the Tammy 17-50 with very similar numbers and the Tammy with a lot more range.

Next I need to look at some pictures.

Tammy 17mm @ 5.6

It doesn't have the blues and greens, nor give the impression of lush, full colours, that an SMC Pentax lens does, though is otherwise fine for colour and saturation. Images tend to look like they have a lot of yellows and browns.







FA 31 Ltd. 1.8





I think reading through the reviews the biggest thing pushing me towards the 31 Ltd over the Tamron 17-50 would be the superior bokeh.. and if you're selling your images that's a big thing. But I'm seriously thinking of picking up both these lenses.

[Frogfish]

Rather than go for the 31 Ltd ( I now have the other two FA Ltds) I instead went for the Sigma 30/1.4 and Zeiss 28/2.8, which has been compared favourably to the 31 https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/154533-shootou...teds-peer.htmland is a fantastic landscape lens (though MF) instead. So I got not only a great landscape lens but also the wonderfully creative f1.4 of the Sigma. All for a few hundred less than the cost of the 31 alone. Tough call though.

[normhead]

I see what you're saying there Frogfish but... the flower shot, the bokeh is so much better on the 31 ltd. You can really see that unmeasurably sharp centre on the 31 ltd on the barn shot... the Zies is sharper on the corners.. overall with the colours I'd say I like the 31 ltd better, across the full range of shots, to the point that I'd use those an example of why I like pentax lenses.

These two images... the difference in bokeh for me sells the 31 ltd. The colour is subjective.. I like the Pentax colour rendition better , but maybe that's correctable in PP, and maybe it's just me...

The bokeh comparison however is enough to sell the lens, if you're looking for versatility. I can see printing the Pentax image on a card... the Zies image, not so much without blurring the background in PP. I'm noticing the lighting isn't the same on both shots... Pentax image blasted highlights in full sun, Zies exposure much better controlled. Tell that dude to check his histograms next time.

Zies



Pentax bokeh

[Frogfish]

I see what you're saying there Frogfish but... the flower shot, the bokeh is so much better on the 31 ltd.

These two images... the difference in bokeh for me sells the 31 ltd. The colour is subjective.. I like the Pentax colour rendition better , but maybe that's correctable in PP, and maybe it's just me...

The bokeh comparison however is enough to sell the lens, if you're looking for versatility. I can see printing the Pentax image on a card... the Zies image, not so much without blurring the background in PP.

Colour is of course correctable in PP - still its easier when it comers straight out of the camera the way you like it ! That of course though does spend to a certain extent on whether you are shooting in RAW or jpg.

Bokeh. Well of course both were shot wide open so it's the Pentax's f1.9 vs the Zeiss' f2.8 ! But as you pointed out it's because the Zeiss is so sharp all across the frame that it's a great landscape lens. It really depends on what you are looking for.