Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-28-2010, 03:34 PM   #1
Veteran Member




Join Date: Jan 2009
Location: Canada
Posts: 1,255
Pentax DA* 55mm 1.4 SDM (unscientific test)

EDIT: Here's something potentially more interesting: http://tinyurl.com/cavzf6 ...Scroll down to see some quick comparisons to Sigma 50 f/1.4.

My intent is to use it in very bad weather, to do short telephoto cityscape and landscape--definitely *not* to shoot cereal boxes. Note: "real-life" (from target to target, modulo hunting) focusing didn't seem much slower than Sigma 50 f/1.4 HSM (EDIT: but it was noticeably slower).

Since at f/1.4, AF is unreliable and focus bracketing is pretty futile, shooting ISO resolution test charts at f/1.4 is probably bogus...So in the eternal struggle of cereal box vs. lens, I chose to shoot 3d objects and crop whatever seemed in focus. Good MTF numbers are good, but bad ones aren't necessarily a cause for concern (EDIT: I'm especially talking about border numbers, because of field curvature).

Conclusion: There is plenty of contrast (for f/1.4)--in in-focus areas--but the lens is unsurprisingly not apochromatic. I also own the other "modern 50" by Sigma which is also very sharp. YMMV. The lens is definitely expensive, maybe too expensive, but the other weather sealed 50 is Canon's f/1.2 (which is soft by many accounts)... BTW, I think these kinds of posts are bad mojo for the SDM motor...

EDIT: OK, first something pretty (also at f/1.4)



100% crops (All handheld, shot with K20D, wide open.)

Near center (~0.45m away from me, a printout at ~45 degree angle):

Extreme left edge:

Near center:

Extreme top edge (the yellow lettering is in focus, sorry about the noise):



Last edited by asdf; 01-29-2010 at 01:23 PM.
01-29-2010, 03:17 AM   #2
Veteran Member
blende8's Avatar

Join Date: Feb 2007
Location: Bremen, Germany
Photos: Albums
Posts: 1,484
I am not sure what your intention is with this post.
Are you satisfied? Or not?
Do you want our assessment?
There are no EXIF data.

Since you are so fortunate to own both lenses it would be best to compare them directly, on a tripod.

Could you be a bit more precise regarding your statement:
Note: "real-life" focusing didn't seem much slower than Sigma 50 f/1.4 HSM.
What are the differences?

It is possible that Pentax has programmed slight AF corrections for the different apertures of the DA55.
This way the DA may be a bit better with AF compared to the Sigma.
Is this the case?
Are you satisfied with the AF of the Sigma at f1.4?
01-29-2010, 04:46 AM   #3
Veteran Member




Join Date: Jan 2009
Location: Canada
Posts: 1,255
Original Poster
QuoteOriginally posted by blende8 Quote
Could you be a bit more precise regarding your statement:
Note: "real-life" focusing didn't seem much slower than Sigma 50 f/1.4 HSM.
What are the differences?
It is slower... I can do more checking...

QuoteQuote:
Are you satisfied with the AF of the Sigma at f1.4?
I tried a comparison under my kitchen lights just now and AF was inaccurate with both the Pentax and Sigma (blame the K20D).

OK...so I did a bit of MF focus bracketing. I still couldn't nail focus with either of the Sigma or the Pentax. The Sigma crop has a bit of green and the Pentax a bit of purple, still (not perfect focus). I gave up.

BTW, I did move the tripod to get a similar size. (EDIT: On second look, I didn't move the tripod close enough with the Sigma. BTW, my impression is that both lenses do well, wide open.)

Sigma 50 (100% crop near center, f/1.4, 1/8 sec, ISO100, 2 second mirror lockup, tripod, cable switch)

Pentax 55 (100% crop near center, f/1.4, 1/8 sec, ISO100, 2 second mirror lockup, tripod, cable switch)

Last edited by asdf; 01-30-2010 at 06:32 AM.
01-29-2010, 05:21 AM   #4
Veteran Member




Join Date: Jan 2009
Location: Canada
Posts: 1,255
Original Poster
QuoteOriginally posted by blende8 Quote
Since you are so fortunate to own both lenses it would be best to compare them directly, on a tripod.
Just a quick observation about (background) bokeh: Sigma has a creamy bokeh (good sometimes) but onion shaped circles of confusion (they could look ugly to some, if they're big).

Order of images: Sigma, Pentax, Sigma, Pentax.

Attached Images
       

Last edited by asdf; 01-29-2010 at 09:09 AM.
01-29-2010, 12:21 PM   #5
Veteran Member
blende8's Avatar

Join Date: Feb 2007
Location: Bremen, Germany
Photos: Albums
Posts: 1,484
QuoteOriginally posted by asdf Quote
Just a quick observation about (background) bokeh: Sigma has a creamy bokeh (good sometimes) but onion shaped circles of confusion (they could look ugly to some, if they're big).
Very interesting!
Are these from the same position with tripod?
If yes, the difference is remarkable.

I think I must buy the Sigma myself.
01-29-2010, 12:46 PM   #6
New Member




Join Date: Jun 2009
Location: seattle
Photos: Gallery
Posts: 23
this thread is giving me a headache....(mainly, because i can't understand what the poster is trying to say)
01-29-2010, 01:12 PM   #7
Veteran Member




Join Date: Jan 2009
Location: Canada
Posts: 1,255
Original Poster
QuoteOriginally posted by blende8 Quote
Very interesting!
Are these from the same position with tripod?
If yes, the difference is remarkable.

I think I must buy the Sigma myself.
I moved the tripod so that the size of the target was the same. I attached new 100% crops, but this time, the shots were done without moving the tripod. Sigma's behavior is unlike any other fast 50 that I know.

BTW, I'd use the Sigma, in situations in which there were no background points of light--I don't like the onions.

QuoteOriginally posted by rams Quote
this thread is giving me a headache....(mainly, because i can't understand what the poster is trying to say)
Sorry mate. Which part did I obfuscate most? Sorry, for making the thread a blur...
Attached Images
   
01-29-2010, 02:20 PM   #8
Veteran Member
blende8's Avatar

Join Date: Feb 2007
Location: Bremen, Germany
Photos: Albums
Posts: 1,484
What's really interesting here is that the Sigma has a noticeably smoother bokeh compared to the DA. It appears that the circles of confusion are larger.
The question is why?
Interesting!

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!
55mm 1.4 sdm, center, edge, f/1.4, focus, k-mount, lens, pentax da* 55mm, pentax lens, sigma, slr lens, target, test
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
New 55mm SDM 645D lens means no SDM II? alehel Pentax News and Rumors 11 03-14-2010 09:43 AM
my unscientific lazy man's ltd lens test nostatic Pentax SLR Lens Discussion 4 12-30-2008 07:35 PM
Pentax 300mm f/4 SMCP-DA* ED IF SDM AF: Lens Test Clicker Pentax SLR Lens Discussion 3 09-20-2008 08:58 AM
Lens Test: Pentax SMCP-DA* 200mm f/2.8ED (IF) SDM AF MikePerham Pentax SLR Lens Discussion 1 05-24-2008 02:33 PM
Unscientific test of firmware versus autofocus Rick Pentax DSLR Discussion 17 05-13-2007 11:41 PM



All times are GMT -7. The time now is 04:43 AM. | See also: NikonForums.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