Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
03-30-2015, 03:29 PM   #1
Site Supporter
Site Supporter
sholtzma's Avatar

Join Date: Sep 2007
Location: Salisbury, NC
Photos: Gallery | Albums
Posts: 1,024
Is this copy of FA20mm good enough?

After using my DA 12-24 much more than I expected when on a trip, and with another trip upcoming, I wondered if I could find a sharper, better WA lens. I just picked up an FA 20mm f2.8 and want to get your judgment about its sharpness (and any other criteria you wish to comment on).

The first image, of a yard, was shot at low ISO, high shutter speed, and f2.8. Handheld, with SR. Focus was intended to be on the birdbath roughly 20-25 feet away. Then there are crops of the birdbath area near the center and of an edge that should have included the plane of focus.

The next set of images, of a piece of metal wall art hanging on an outside wall about 2-3 feet away, were controlled. Camera was on a tripod, without SR, and with self-timer at 2 seconds. Focus was on the area near the center that I then show cropped. Various ISO and shutter speeds were used to test the lens at f2.8, f4, f5.6, and f8.

All images shot in RAW and processed in ACR 4 using only the defaults, then resized to fit the PF guidelines.

To be fair, I expect I'd use this lens not so much close up as at or near infinity--for landscapes, scenic, architecture, and the like.

Are my tests fair so far? Should I test it further? What do these tests show, especially for those of you who have (and who rave over the sharpness of) this lens?

Attached Images
View Picture EXIF
PENTAX K-5 II s  Photo 
View Picture EXIF
PENTAX K-5 II s  Photo 
View Picture EXIF
PENTAX K-5 II s  Photo 
View Picture EXIF
PENTAX K-5 II s  Photo 
View Picture EXIF
PENTAX K-5 II s  Photo 
View Picture EXIF
PENTAX K-5 II s  Photo 
View Picture EXIF
PENTAX K-5 II s  Photo 
View Picture EXIF
PENTAX K-5 II s  Photo 
View Picture EXIF
PENTAX K-5 II s  Photo 
03-30-2015, 03:31 PM   #2
Site Supporter
Site Supporter
sholtzma's Avatar

Join Date: Sep 2007
Location: Salisbury, NC
Photos: Gallery | Albums
Posts: 1,024
Original Poster
And here is the wall art image shot at f8 along with its center crop...
Attached Images
View Picture EXIF
PENTAX K-5 II s  Photo 
View Picture EXIF
PENTAX K-5 II s  Photo 

Last edited by sholtzma; 03-30-2015 at 03:48 PM.
03-30-2015, 04:52 PM   #3
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 11,183
Are you sure the aperture is stopping down correctly? Make sure the aperture ring is in A position (press little button) and make sure the camera successfully stops it down.
You can try another test where you take a photo of a newspaper or something laid near the minimum focus distance at a 45 degree angle to the sensor plane. Try to position it such that the focus is near the middle of the page. That way you can see whether the text is sharp, how the DoF changes, and so on. Take one photo wide open and one at f8.
Beyond that, I cannot help since I don't have that lens. It does seem a little soft, then again it is an UWA and might need some PP
03-30-2015, 05:14 PM   #4
dms
Site Supporter
Site Supporter




Join Date: Aug 2011
Location: New York, NY
Photos: Gallery
Posts: 2,004
I suggest you take pictures with same FL with both lenses--zoom and 20 mm, at about f/5.6, at intermediate distance and infinity with careful focusing (maybe use the lens scale if you have trouble manual focusing). Pick something like trees with lots of branches in the distance, and for the intermediate distance something with a lot more surface texture. And then view/post at 100%. Actually the pictures you post seem very low in resolution and/or contrast.

03-30-2015, 05:31 PM   #5
Site Supporter
Site Supporter
sholtzma's Avatar

Join Date: Sep 2007
Location: Salisbury, NC
Photos: Gallery | Albums
Posts: 1,024
Original Poster
I can confirm that the lens passes all its mechanical and "eye" tests. Glass is clear with little dust. Aperture blades are snappy and clean. Aperture stops down correctly by hand, and the camera reads that it is stopping down the lens electronically. Focus ring moves smoothly throughout the range, and again, on the camera it reads in focus quickly and at all distances. The lens shows very little wear externally.

I can try the newspaper test. I cannot compare this lens with my zoom, since KEH is re-repairing the zoom for another week or so.

I don't want to have unrealistic expectations for this lens, but I'm willing to send it back if it's not what it should be. Or, perhaps it just needs to be sent in for adjustment?
03-30-2015, 05:50 PM   #6
Veteran Member




Join Date: Jul 2013
Posts: 1,457
For a FA 20mm 2.8 ??? I personally thought it just isn't quite there.....looked a tad bit soft to me.
Sorry , but that was my first impression looking at the crops.
It all depends on what YOUR expectations are and what YOUR going to be using it for......So only YOU can figure out if its a keeper or not !
I would try adding some in camera lens profile correction on it and see if that helps ?
Also......your shooting a wall close ......so is it focusing on the wall , or on the decorative metal ? Remember ...even though WA lenses have incredible depth of field , up close that diminishes the loser you get !
Something just does not look right its not got much contrast and the yard shots are just dull and lack sharp resolution.
Don't give up.....test it very very thoroughly before passing judgment for the final call !

Last edited by Dlanor Sekao; 03-30-2015 at 06:04 PM.
03-30-2015, 06:02 PM   #7
Site Supporter
Site Supporter
sholtzma's Avatar

Join Date: Sep 2007
Location: Salisbury, NC
Photos: Gallery | Albums
Posts: 1,024
Original Poster
QuoteOriginally posted by Dlanor Sekao Quote
For a FA 20mm 2.8 ??? I personally thought it just isn't quite there.....looked a tad bit soft to me.
Sorry , but that was my first impression looking at the crops.
It all depends on what YOUR expectations are and what YOUR going to be using it for......So only YOU can figure out if its a keeper or not !
I would try adding some in camera lens profile correction on it and see if that helps ?
Also......your shooting a wall close ......so is it focusing on the wall , or on the decorative metal ?
Something just does not look right its not got much contrast and the yard shots are just dull and lack sharp resolution.
Don't give up.....test it very very thoroughly before passing judgment for the final call !
Well, that's my first impression too: something just isn't right. But, yes, you are right; I will test it much further and in a variety of different ways. My basic criterion is that it needs to be significantly better than the 12-24, or else it's not worth my keeping it.

Should I have send it to KEH for alignment/adjustment?
03-30-2015, 06:08 PM   #8
Veteran Member




Join Date: Jul 2013
Posts: 1,457
QuoteOriginally posted by sholtzma Quote
Well, that's my first impression too: something just isn't right. But, yes, you are right; I will test it much further and in a variety of different ways. My basic criterion is that it needs to be significantly better than the 12-24, or else it's not worth my keeping it.

Should I have send it to KEH for alignment/adjustment?
Try an in camera lens correction profile first.
And test it about 6' on a flat wall with something of texture and moderate contrast.
If it doesn't meet your expectations .........send it back !
I went through a similar dilemma with a Samyang 14mm and it ended up being a keeper.
Don't give up too quick until all the variables are covered.

03-30-2015, 06:10 PM   #9
dms
Site Supporter
Site Supporter




Join Date: Aug 2011
Location: New York, NY
Photos: Gallery
Posts: 2,004
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***)
f/2.8
55
55/55
49/49
49/44
44/39
f/4
78
78/69
69/55
49/49
49/39
f/5.6
78
78/78
78/69
69/62
62/55
f/8
78
78/78
78/78
69/69
69/55
f/11
78
78/78
69/62
69/62
55/49
f/16
69
62/62
62/62
55/49
49/44
f/22
55
49/49
49/44
44/39
39/35
03-30-2015, 08:08 PM   #10
osv
Veteran Member




Join Date: Mar 2007
Location: So Cal
Photos: Gallery
Posts: 2,080
QuoteOriginally posted by sholtzma Quote
Are my tests fair so far? Should I test it further? What do these tests show, especially for those of you who have (and who rave over the sharpness of) this lens?
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.
03-30-2015, 08:32 PM   #11
csa
Loyal Site Supporter
Loyal Site Supporter
csa's Avatar

Join Date: Aug 2014
Location: Montana mountains
Posts: 9,708
I've taken the liberty of sharpening this photo. You can see the original was very soft.
Attached Images
View Picture EXIF
PENTAX K-5 II s  Photo 
03-30-2015, 08:39 PM   #12
Site Supporter
Site Supporter




Join Date: Jul 2009
Location: Los Angeles, CA USA
Photos: Gallery | Albums
Posts: 675
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?
03-30-2015, 08:45 PM   #13
Site Supporter
Site Supporter




Join Date: May 2012
Location: Adelaide
Photos: Gallery | Albums
Posts: 1,242
Was this with autofocus done through the viewfinder or with live view? Auto-focus calibration needs to be eliminated as a contributing factor to any apparent softness before an opinion can truly be passed on the lens alone. If not done already, test with live view focus and see if the results improve. Better still if you can pop the camera on a tripod and use the 2 second timer to eliminate camera movement. Also, if you were autofocusing through the viewfinder, did you use spot focus with the garden scene or multipoint focus (which could have selected a target some distance away from the birdbath).
03-31-2015, 04:36 AM   #14
Veteran Member




Join Date: Sep 2013
Location: Sydney
Photos: Albums
Posts: 844
I've got an A20, and my opinion of it is quite low. It's not particularly sharp, and contrast is a bit lacking. The DA12-24, and DA21 are in a different league. The older M20 and K18 are somewhere inbetween. (My opinion on having owned all of them)

Your tests appear to match my experience with the A20. It's a bit underwhelming, and I'm not sure why it scores so highly on PF reviews. Maybe it's just been out resolved by the k5/k3? I did find that a circular polariser was a must for that lens on apsc though. But even then it can't match the DA21.
03-31-2015, 05:47 AM   #15
Pentaxian
Na Horuk's Avatar

Join Date: Feb 2012
Location: Slovenia, probably
Photos: Gallery | Albums
Posts: 11,183
QuoteOriginally posted by robthebloke Quote
Maybe it's just been out resolved by the k5/k3?
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
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
aperture, center, copy of fa20mm, design, f/2.8, f2.8, f8, feet, focus, images, k-mount, lens, pentax lens, pf, pp, results, sharpness, slr lens, test, tests, uwa, wall
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
A Good Copy Of This Lens (135mm Super Takumar)? Jim Rodgers Pentax SLR Lens Discussion 2 03-16-2012 05:43 PM
Is this Tripod good enough? Wilson_Kx Pentax Camera and Field Accessories 9 05-11-2010 03:34 AM
what is a good or bad copy of Da*16-50? nuaabill Pentax SLR Lens Discussion 20 11-13-2009 07:26 PM
DA*16-50... Is this a good copy??? Urgent! Apfel Pentax SLR Lens Discussion 4 08-30-2008 04:47 PM
Is your monitor good enough for this forum? falconeye General Talk 24 04-01-2008 12:08 AM



All times are GMT -7. The time now is 09:36 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top