Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
11 Likes  
DA lenses on Full Frame: Test Shots thread
Posted By: falconeye, 07-07-2008, 02:50 PM

Hi everybody,

I would like to open up a thread dedicated to one topic:

DA lens on Full Frame: a sticky test shots thread.

This thread shall be dedicated to test shots of a DA lens mounted to a full frame body (e.g., a film camera body). By test shot, I mean shots dedicated to evaluate the performance. Shots of ordinary subjects aren't suitable to this task, normally, and should not be posted. So, these are the rules:
  • K mount lens dedicated to the APS-C form factor is used.
  • Image is taken full frame 36mm x 24mm.
  • Lens hood was removed.
  • And ideally, no filter is mounted.
  • The aperture used is specified (note that film cameras don't record EXIF...).
  • Sample image shows the entire field of view.
  • Sample image(s) show(s) corner, border and center performance at 10MP-100% (multiple crops, or single not-resized image).
  • The subject is such that resolution and vignetting at the borders can be compared to the center.
The idea behind this thread is obvious: To compile enough data to assess the spectrum of available lenses for a forthcoming full frame DSLR in K mount.

#################################################

Table of results as obtained in this thread (updated regularly):
SMC Pentax-DA primes...
SMC Pentax-DA zooms...
Sigma K mount DC...
  • Sigma 18-200mm f/3.5-6.3 DC: -
  • Sigma 10-20mm f/4-5.6 DC: - (below 14mm, Gooshin)
  • ...
Tamron K mount Di-II...
  • ...
Overall rating scale:
+++: no significant difference between APS-C and FF corners
++: difference but usable at full aperture with a small loss in corner IQ only
+: usable staring at f/4~f/5.6, with no or a small loss in corner IQ only
o: usable at f/11 or with big loss in corner IQ only
-: not usable


Last edited by falconeye; 07-20-2016 at 02:57 AM. Reason: Result table updated
Views: 312,140
02-10-2009, 07:22 PM   #91
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 8,934
QuoteOriginally posted by falconeye Quote
Note that 3000 LW/PH is the K20D sensor's resolution.
How did you calculate that?

The K20D's sensor has 3104 visible vertical pixels.

I'm assuming that 3000 LW/PH means that 3000 line widths are resolved across the vertical length of the picture with a 50% loss of relative contrast.

I'm further assuming that 1.3 x the number of line widths will cause a contrast loss of 50%. If I see 1.3 N line width through a N line width grid, then each grid line blurs 1 + 1/3 line widths so the contrast between adjacent grid line widths should be 1/3 : 2/3 = 0.5 (50%).

That would give me 4035 LW/PH but only for a black and white image and assuming that RAW data is evaluated (i.e., omitting any demosaicing).

Due to the bayer array structure of the sensor, the colour resolution will be reduced. The minimum should be 2017 LW/PH but the real LW/PH figure should be somewhere between 2017-4035 values as interpolation can recover information. For instance, for say image positions occupied by red pixels by using information from adjacent green pixels. How much colour resolution can be resolved will depend on the demosaicing algorithm.

All this omits the anti-aliasing filter which will reduce the LW/PH figure.


Last edited by Class A; 02-10-2009 at 07:34 PM.
02-11-2009, 05:00 AM   #92
Pentaxian
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,862
Original Poster
QuoteOriginally posted by Class A Quote
How did you calculate that?
The K20D's sensor has 3104 visible vertical pixels.
Thanks for the insightful comments.

Actually, I just wanted to say that "3104 pixels" and "3000 LW/PH" are close numbers. Contrast doesn't matter much because the iso chart lets you pick the closest line pair you can still distinguish. So, it's rather a 5% contrast figure.

Regarding your 1.3x thought experiment: It would map 4 LW of infinite contrast (2 line pairs) onto 3 pixels showing 1 line pair (2 LW) at 3:1 contrast (or less). In general, you'll get Moiré. You can't get beyond the critical frequency of the Nyquist–Shannon sampling theorem.

On more pratical terms:
If evaluating the iso test chart, take care to not only distinguish the lines, but count them, too (i.e., watch out for Moiré patterns)!
02-19-2009, 03:23 AM   #93
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 8,934
QuoteOriginally posted by falconeye Quote
You can't get beyond the critical frequency of the Nyquist–Shannon sampling theorem.
The Nyquist-Shannon sampling theorem states the frequency required (2x highest signal frequency) required in order to allow an exact reconstruction of the signal. I haven't seen a form of it which accounts for an admissable loss in contrast of the signal.

But you are right, in my thought experiment the number of observed lines is less than the actual number of lines which must not happen.

Assuming that actual lines are spaced apart with a distance that is equal to their width then one cannot resolve more LW/PH than the sensor has vertical pixels (and even that requires B&W RAW processing). One could reduce contrast by choosing smaller lines but it would not be admissible to reduce the spacing between the lines accordingly (only by a minute factor, < * 1 / #vertical pixels).

QuoteOriginally posted by falconeye Quote
If evaluating the iso test chart, take care to not only distinguish the lines, but count them, too (i.e., watch out for Moiré patterns)!
Right, otherwise one may not recognise spurious resolution.
04-06-2009, 02:44 PM   #94
Veteran Member
Gooshin's Avatar

Join Date: Sep 2007
Location: Toronto, the one in Canada.
Posts: 5,611
adding to the database...


this is the Pentax 10-17 FE at 10mm on a pentax MZ-S



04-06-2009, 04:31 PM   #95
Pentaxian
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,862
Original Poster
QuoteOriginally posted by Gooshin Quote
adding to the database...
this is the Pentax 10-17 FE at 10mm on a pentax MZ-S
Thanks, this is a nice and welcomed addition.
Cf. post #59 (https://www.pentaxforums.com/forums/344170-post59.html) which lacked an image.

Looks like there would be a lot of extra image exposed w/o the lens hood

Post #61 showed the effect for a Tokina 10-17 (https://www.pentaxforums.com/forums/345566-post61.html).

Is the lens hood of the Pentax DA 10-17 FE removable?
04-06-2009, 08:34 PM   #96
Veteran Member




Join Date: Feb 2008
Location: Toronto
Posts: 3,915
nope... but some people have sawed it off
04-07-2009, 10:29 AM   #97
Veteran Member
Gooshin's Avatar

Join Date: Sep 2007
Location: Toronto, the one in Canada.
Posts: 5,611
QuoteOriginally posted by falconeye Quote

Is the lens hood of the Pentax DA 10-17 FE removable?
as Simon pointed out, if you are good with delicate tools, its doable.
05-07-2009, 06:20 PM   #98
Senior Member
eyou's Avatar

Join Date: Feb 2009
Posts: 224
so any news on the latest DA lenses? (DA* 55, DA* 60-250, DA limited 15)

05-08-2009, 12:34 AM   #99
Pentaxian
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,862
Original Poster
Thanks to Steelski post #86, I think we know that the DA*55 doesn't vignette and may have a lens hood made for FF. Seems to be a "+" or better. Not much else yet.

No news for the other two lenses. I don't expect the DA15 to be FF capable. Too small. But I don't actually know.
05-11-2009, 03:15 PM   #100
Pentaxian
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,862
Original Poster
According to Asahiflex and this post:
https://www.pentaxforums.com/forums/591340-post13.html
the DA* 60-250 mm is a full frame lens.
07-24-2009, 10:30 AM   #101
Veteran Member




Join Date: Feb 2008
Location: Toronto
Posts: 3,915
DA*55 1.4

07-24-2009, 11:51 AM   #102
Veteran Member
kristoffon's Avatar

Join Date: Aug 2008
Location: Brazil
Posts: 532
QuoteOriginally posted by k100d Quote
DA*55 1.4
Is that vignetting or just uneven lighting? Hard to tell.
07-25-2009, 12:26 PM   #103
Veteran Member




Join Date: Feb 2008
Location: Toronto
Posts: 3,915
QuoteOriginally posted by kristoffon Quote
Is that vignetting or just uneven lighting? Hard to tell.
i realized after that it wasn't the best sample shot, i was trying to see what it looked like wide open more than anything else. i believe in the top left corner, the image is still fairly bright, so the amount of vignetting should be acceptable.
i had to use Tv mode and MF on my MZ-S to force it to shoot wide open.
08-15-2009, 12:33 AM   #104
emr
Guest




Boris Liberman has produced great examples of DA lenses on full frame, as you all probably know. Now what I'd like to know is what is it that causes the strangely shaped vigneting at DA 10-17mm fisheye's wide end? http://liberman-family.com/boris/da_on_film/DA10_17_10_220.jpg Is it due to the lens's internal structures or does it come partially from the hood?
08-18-2009, 08:16 AM   #105
Veteran Member
Gooshin's Avatar

Join Date: Sep 2007
Location: Toronto, the one in Canada.
Posts: 5,611
QuoteOriginally posted by emr Quote
Boris Liberman has produced great examples of DA lenses on full frame, as you all probably know. Now what I'd like to know is what is it that causes the strangely shaped vigneting at DA 10-17mm fisheye's wide end? http://liberman-family.com/boris/da_on_film/DA10_17_10_220.jpg Is it due to the lens's internal structures or does it come partially from the hood?
its from the hood.

if you remove the hood you get a full circle
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!
60-250mm, aperture, bodies, body, camera, corner, da, da*, da* 60-250mm, f2.8, f4, ff, film, flickr, focus, frame, k-mount, lens, lenses, op, pentax, pentax lens, pm, post, sdm, sensor, shots, slr lens, tests, thread
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
DA Lenses on Full Frame (DA 35 ltd) Painter Pentax Full Frame 18 05-29-2016 04:42 PM
DA lenses on Full Frame hjoseph7 Pentax SLR Lens Discussion 6 12-03-2014 01:14 PM
TEST: smc PENTAX DA 35mm 2.8 Macro Limited on Full Frame vjacesslav Pentax SLR Lens Discussion 2 03-17-2012 06:41 AM
DA lenses on Full Frame: Test Shots falconeye Pentax Lens Articles 0 07-07-2008 02:50 PM
DA lenses on full frame sensor ZigDaPig Pentax DSLR Discussion 16 01-05-2008 11:22 AM



All times are GMT -7. The time now is 02:27 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