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03-31-2015, 06:26 AM   #16
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First of all this is a rather dumb idea in my opinion to expect an outstanding crispness and sharpness form shots in these circumstances. Here are points to consider ( apart form the obvious, that e.g. lens is hazy/dusty or misaligned/faulty ) :

a) such wide focal length ( it has to pack an awful amount of data into a frame with only so much pixels
b) such bad scene with flat light and almost no side lighting that would accentuate any details
c) such wide aperture ( I mean f2.8 for 20mm ?? ) this is good for low light just-to-get-the-shot scenes, not for real life day-light photographs
d) and finally - uploading system is VERY BAD on this forum, it will reduce image quality DRASTICALLY - try hosting on flickr or elsewhere and direct-link from there

03-31-2015, 09:52 AM - 1 Like   #17
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QuoteOriginally posted by Na Horuk Quote
This is possible. Modern cameras have high pixel density, no AA filter.. so old UWA designs will struggle more than modern UWA lenses.
Adding a polarizer might help with contrast, and a lens hood as well (a hood for equivalent FoV, so for 30mm). You can PP to add contrast, clarity, and sharpness, make a profile to reduce CA (this will improve sharpness as well) and fringing. If you do all of this, the lens could be acceptable and good.

If I had just gotten that lens and those tests are correct (as in, no other variables affected sharpness other than lens), then I would really think about the lens as well. It being a little soft at f2.8 is expected (UWA, old design) but by f5.6 and f8, I would want it to be sharper. Then again, the Samyang 14mm spoils me
Anyway, I would make sure the aperture is really really correct. In a relatively dark room, choose the lowest ISO, f8 and a long shutter time, then just look into the lens as the camera takes the photo to make sure the aperture is stopped down correctly. Because that is the main problem for me with those sample photos - the image doesn't improve that much from f4 to f8
Let's eliminate the aperture question. I can confirm that the camera (K5IIs) is controlling the aperture correctly.

On the PF lens reviews, there are certainly members who shoot this lens on modern bodies and get great results, even wide open. So, I'm not inclined to believe that any problems with the lens are due to it being an older design.

You are right that I have not added any filtering or done anything in PP yet with the results of this lens. I was more interested in SOOC results for now. If what I am seeing so far SOOC is what I will have to live with, but PP corrects the problems to a sufficient degree, then yes, I will keep the lens.

---------- Post added 03-31-2015 at 12:54 PM ----------

QuoteOriginally posted by dms Quote
The following are the tests by Yoshihiko Takinami, and as you see f/2.8 is low in resolution. Although your outdoors pictures seem low in contrast and resolution even for f/2.8. Nevertheless you should not expect much wide open in a rather fast 20 mm lens of older optical design. I suggest you use f/8 and repeat your tests.
smc PENTAX-A 20mm f/2.8 (A20/2.8, #5863***) [
Then why do so many PP members who have posted lens reviews of this lens rave about it even wide open?

QuoteOriginally posted by lmd91343 Quote
Do you have a tripod? Remote control/cable release? Do you have a shot of a newspaper taped to a wall visible in both the corner and center?
Yes, the wall art shots were taken on a tripod with the timer, but I can add a remote control instead.

I will be glad to test the lens with a newspaper taped to a wall; perhaps better would be a test chart taped to a wall. And I will include that in the tests to be done. But that will test only its close focusing. I'd probably need to add a large wall taken at near infinity; we have a large mural in our town, so I can shoot that too.

---------- Post added 03-31-2015 at 12:59 PM ----------

QuoteOriginally posted by osv Quote
upload the original unaltered birdbath pic to a place like dropbox, where people can download it and look at it.

if you are going to be shooting outdoor landscapes, then post up test shots of big wide landscape pics to that upload link.
I have now created a Dropbox file and will be posting unaltered TIFFs to it for PF folks to inspect.

---------- Post added 03-31-2015 at 01:02 PM ----------

QuoteOriginally posted by manntax Quote
First of all this is a rather dumb idea in my opinion to expect an outstanding crispness and sharpness form shots in these circumstances. Here are points to consider ( apart form the obvious, that e.g. lens is hazy/dusty or misaligned/faulty ) :

a) such wide focal length ( it has to pack an awful amount of data into a frame with only so much pixels
b) such bad scene with flat light and almost no side lighting that would accentuate any details
c) such wide aperture ( I mean f2.8 for 20mm ?? ) this is good for low light just-to-get-the-shot scenes, not for real life day-light photographs
d) and finally - uploading system is VERY BAD on this forum, it will reduce image quality DRASTICALLY - try hosting on flickr or elsewhere and direct-link from there
I am sensitive to all of these concerns. So, let's take them in turn.

a) Perhaps I am expecting too much from this lens, but numerous PF lens reviews exalt this lens' sharpness and crispness.
b) I will ensure that some test shots of larger scenes have more modeled lighting.
c) see my response to a)
d) I have created a Dropbox site at which I will have unaltered TIFFs for PF sleuths to examine.
03-31-2015, 12:43 PM   #18
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See the following dropbox album. I found I still had my 12-24mm, so I made some comparison shots today. All shots between the lenses were made at the same settings, except for some reason the 20mm mark on my zoom actually produces 19mm shots, and aside from the obvious point that the zoom doesn't go down to f2.8. Other than that, they should be fully comparable. All shots on a tripod, with mirror lock up, and remote control of the shutter. All shots at 80 ISO. No filters, no PP. No hood on either lens, but no lens was pointed at a light source, and I shielded each lens from as much indirect light as I could. All shots loaded into Photoshop with ACR 4.0 on its defaults, and then saved as TIFFs.

The first five shots are from the other day, which sparked the discussion earlier in this thread....

https://www.dropbox.com/sc/2foj8ftix1is019/AABVSzs4mNx0lGElz2_mgkHra
03-31-2015, 01:56 PM   #19
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QuoteOriginally posted by sholtzma Quote
The first five shots are from the other day, which sparked the discussion earlier in this thread.... https://www.dropbox.com/sc/2foj8ftix1is019/AABVSzs4mNx0lGElz2_mgkHra
I just checked your dropbox , and was particularly interested how lens fares against this brick wall with focusing chart @ F/4 so I downloaded the full size tiff from here (https://www.dropbox.com/sc/2foj8ftix1is019/AABVSzs4mNx0lGElz2_mgkHra#lh:29-t...%20at%20f4.tif)

My conclusion : lens is fine, very good resolution, maybe low-ish contrast but that still decent , considering it was not PP-ed in any way. Good detail across the frame.. with corners and edges just touch softer, but that is obvious I think and I guess its gone by F5.6 or 8

I intentionally ignored f2.8 results because they are meaningless in grand scheme of things so to speak :P

You are officially pronounced by me a lucky owner of very nice FA 20mm f2.8 lens !

03-31-2015, 02:53 PM   #20
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I think you are doing some good tests there. The FA 20mm seems better with the latest tests, but the 12-24mm seems to be slightly better, plus it has a whole zoom range. Unless you will use f2.8 or enjoy its compact size, Id say you can return or sell the FA 20mm.
03-31-2015, 04:44 PM   #21
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I just added shots of a very large mural in town, with focus at a considerable distance. It's the usual set: the FA at f2.8, f4, f5.6, and f8, and the DA at f4, f5.6, and f8.

Certainly, my hope was to have a good enough copy of the FA 20 to be able to use it at f2.8 and have it be rather sharp. That's the whole point of a good prime. Should I aim instead at the FA* 24 f2 for wide open sharpness? I like my DA zoom, and although it is not the sharpest lens in the world, it offers a very useful zoom range, constant f4, and small and lightweight design. I need the FA 20 to stand out from the zoom if I am to keep the prime. I much prefer good zooms but will add the extraordinary prime.

So, I hope others will weigh in on their judgments of the lens (especially in comparison with the DA zoom) using the shots in Dropbox. If you need to see other kinds of shots, let me know. I appreciate all input, but please offer justifications (not merely "I like it", "I don't like it").
03-31-2015, 05:27 PM   #22
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I looked at f5.6 and f8.0.......Your lens is quite good and if it were me I wouldn't think of getting rid of it !
However I think your DA may be a tiny bit better.....I cant really say for sure.....its a tough call.

Why be concerned of shooting wide open if your using it for landscapes and architecture as stated ?
But this lens is no slouch within its sweet spot which is not wide open for sure and shouldn't be judged on that alone.
Now....if you should need something super sharp wide open ? Good luck on that one and maybe consider a Samyang 14mm or 24mm ??
03-31-2015, 06:11 PM   #23
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QuoteOriginally posted by Dlanor Sekao Quote
I looked at f5.6 and f8.0.......Your lens is quite good and if it were me I wouldn't think of getting rid of it !
However I think your DA may be a tiny bit better.....I cant really say for sure.....its a tough call.

Why be concerned of shooting wide open if your using it for landscapes and architecture as stated ?
But this lens is no slouch within its sweet spot which is not wide open for sure and shouldn't be judged on that alone.
Now....if you should need something super sharp wide open ? Good luck on that one and maybe consider a Samyang 14mm or 24mm ??
My desire to be able to use the lens wide open turns on the need at times to shoot in low light. For example, in dark situations without a tripod (such as in Greece recently at museums and dark ruins) I did not dare knock the ISO up too high, which required shooting at or near wide open. This was true with all of the lenses I brought. The other two zooms I had function rather well wide open; of course even they are better stopped down one or two stops, but they are sharp enough wide open. That's why I pay for better lenses these days and avoid "consumer" lenses. I want the extra sharpness of good lenses that are useful wide open if needed.

Again, if the FA20 does not trump my DA zoom, then I have no need for the FA20. I prefer having and carting around only a few lenses that cover a wide range of focal lengths. The only exceptions are a macro prime and a long telephoto prime.

Are the Samyangs noticeably better than the AF Pentax FA 24 f2?

03-31-2015, 07:24 PM   #24
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QuoteOriginally posted by sholtzma Quote
My desire to be able to use the lens wide open turns on the need at times to shoot in low light. For example, in dark situations without a tripod .....
Are the Samyangs noticeably better than the AF Pentax FA 24 f2?
I don't want to get into too much trouble here....But I will say this.....Its at least a draw ! Samyang 24mm f1.4 is amazing !
04-02-2015, 05:35 AM   #25
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Hope others will weigh in on the relative capability of this FA20 vs this DA 12-24....

See the Dropbox photos for comparison: https://www.dropbox.com/sc/2foj8ftix1is019/AABVSzs4mNx0lGElz2_mgkHra
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