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02-22-2014, 09:49 AM   #31
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If you, people, are interested, I can upload real life tests of the following lenses : DA 21 Lim, DA 35 Lim, FA 50, Sigma 28, DA* 16-50, DAL 18-55 WR Kit. The same scene was shot using K-3 mounted on a tripod.

02-22-2014, 10:35 AM   #32
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QuoteOriginally posted by Stagnant Quote
If you, people, are interested, I can upload real life tests of the following lenses : DA 21 Lim, DA 35 Lim, FA 50, Sigma 28, DA* 16-50, DAL 18-55 WR Kit. The same scene was shot using K-3 mounted on a tripod.

Who can say no to that?!

One camera, one scene, six lenses!
02-22-2014, 10:51 AM   #33
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well, if we are going to either refute or correlate the data, then shooting wide-open then stopping down to f/5.6 might let us see if a particular lens behaves the way the data says it should!

Thanks for the offer! -- would love to see how these puppies compare to each other.

M
02-22-2014, 02:26 PM   #34
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Here is an archive which contains images produced by the lenses I mentioned in the previous post. The file is big - 3.08 GB.

Content :

SMC Pentax-DA* 16-50mm F2.8 ED AL [IF] SDM

16 mm, 18 mm, 21 mm, 28 mm, 34 mm, 36 mm, 50 mm

Due to a mechanical defect of my copy, I was not able to dial exactly 35 mm. Also there were some problems with sharpness in the range from 34 to 36.

SMC Pentax-DA L 18-55mm F3.5-5.6 AL WR

18 mm, 21 mm, 28 mm, 35 mm, 50 mm

SMC Pentax-DA 21mm F3.2 Limited

SMC Pentax-DA 35mm F2.8 Limited Macro

SMC Pentax-FA 50mm F1.4

I included two sets. One is shot using central focus point, while the other has focus on the most remote object in the scene. Technically they both are infinity, but I noticed some differences in resulting images.

Sigma 28mm F1.8 Aspherical II

All the lenses were shot from their widest apperture to F10. The camera was mounted on a tripod and a remote control was used. ISO 100, Av mode, central focus point, multisegment metering, AWB. RAW files were processed in SilkyPix Developer Studio 5 with default settings.


Last edited by Stagnant; 02-22-2014 at 02:35 PM.
02-22-2014, 06:23 PM   #35
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first observations:

DA 35mm Macro: the corners don't sharpen up until f/8. But strangely, if you look VERY closely at the f/2.8 is is actually slightly sharper in the lower right corner than f/4 or f/5.6 (check out the chain link fence near the garage). Clearly f/8 is the "best" but I wonder why f/4 and f/5.6 in the lower right corner don't quite match? Is there any possibility of slight refocus between exposure here? Or is this a classic case of "focus creep"?

Very interesting.

Michael
02-23-2014, 05:45 AM   #36
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QuoteOriginally posted by MJSfoto1956 Quote
first observations:

DA 35mm Macro: the corners don't sharpen up until f/8. But strangely, if you look VERY closely at the f/2.8 is is actually slightly sharper in the lower right corner than f/4 or f/5.6 (check out the chain link fence near the garage). Clearly f/8 is the "best" but I wonder why f/4 and f/5.6 in the lower right corner don't quite match? Is there any possibility of slight refocus between exposure here? Or is this a classic case of "focus creep"?

Very interesting.

Michael
DA 35 Macro.

At F2,8 it is sharper than at 3,2 and 3,5.
Sharpness improves at 4,0, but not substantially.
F4,5 shows slight improvement in the centre of the frame, while the corners still lag behind.
F5,0 the centre of the frame is now sharper, while the improvement in the corner sharpness is marginal.
F5,6 is where the corner sharpness starts noticeably improving. Centre is top-notch.
F6,3 to F8,0 both corner and centre sharpness improve.
F9,0 is the point where there is no increase in centre sharpness, while the corners are still becoming more detailed.
F10. Diffraction starts to affect the centre of the frame, while the corners are still improving.

With the aperture from 2,8 to 5,6 the sharpness in no uniform across the frame. Some corners are sharper, while the other are softer. This observation makes me wonder.
02-23-2014, 02:49 PM - 1 Like   #37
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DA 21

Up to F 5.6, each next aperture value brings a noticeable improvement of centre sharpness and slightly lower increase in corner sharpness. F5.6 to F8.0 the sharpness in centre of the frame and on the edges improves almost equally. F8.0 to F10, no noticeable changes in the centre of the frame, while the extreme edges keep improving.
02-23-2014, 11:10 PM   #38
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QuoteOriginally posted by monochrome Quote
So I own the DA15 and DA40.

On the basis of percieved resolution what I'm reading is that, within the context of DA Limited lenses, I actually own the two dogs that DxOmark suggests no one should want to own!

Or do I own two lenses dessigned to render pleasing images the classic Pentax way while the others are designed to test well?
Makes you wonder how theses test are performed rather then any lens being a dog.

From Slr Gear
Overall, the 40mm /2.8 is a very sharp lens, never exceeding three blur units and averaging around 1.5. Set to apertures less than /8, some corner softness is visible, surprisingly most at /5.6, where the right side of the frame approaches three blur units, but the center stays sharp as sharp as we can detect at one unit. The lens performs better at /2.8 and /4, where is corner softness is visible, but less significant. At /8 the lens is sharp but for a very slight blur on the right side, and by /11 it's tack-sharp across the entire frame.
Pentax Lens: Primes - Pentax 40mm f/2.8 Limited SMC P-DA (Tested) - SLRgear.com!

And looking at photozone the 40 has very even performance to f11 so just what are DXO showing ?
Pentax SMC DA 40mm f/2.8 Limited - Review / Lab Test - Analysis

Is this some perception of some person who's ability and eyesight we have no idea on , As it seems to me their results are in contradiction of proper documented testing procedures to often to be used for anything other than raising a smile

02-24-2014, 03:01 AM - 1 Like   #39
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Well hey, this is just proof of what many have been saying all along - judge the lens on whether it can fulfill your needs, not how someone else says it performs!
02-24-2014, 10:11 AM   #40
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QuoteOriginally posted by Na Horuk Quote
Well hey, this is just proof of what many have been saying all along - judge the lens on whether it can fulfill your needs, not how someone else says it performs!
Too true. I've also read on the Internet that a gold plated lens cap can improve lens sharpness no end
02-24-2014, 10:21 AM   #41
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I believe that lens tests are conducted on a single copy, which may or may not be representative. The exception would be LensRentals.com, who check several copies of the lens under review.

Last edited by audiobomber; 04-06-2014 at 08:47 AM.
02-24-2014, 10:56 AM   #42
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QuoteOriginally posted by Stagnant Quote
All the lenses were shot from their widest apperture to F10. The camera was mounted on a tripod and a remote control was used. ISO 100, Av mode, central focus point, multisegment metering, AWB. RAW files were processed in SilkyPix Developer Studio 5 with default settings.
There seems to be a bit of front focus on your camera with all the lenses - have you checked it against live view focus at infinity ?
02-24-2014, 12:05 PM   #43
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QuoteOriginally posted by Na Horuk Quote
Well hey, this is just proof of what many have been saying all along - judge the lens on whether it can fulfill your needs, not how someone else says it performs!
QuoteOriginally posted by audiobomber Quote
I believe that lens tests are conducted on a single copy, which may or may not be representative. The exception would be Lenstip, who check several copies of the lens under review.
Lenstip is an outstanding site IMO. Reviews and sample photos from others are often the only way we can guess whether a lens will meet our needs before buying it. Let's use the FA 43 as an example. Most users give it high marks. For astrophotography, though, it's a dog because of too much coma distortion. Many reviews don't mention coma because it's invisible during daylight. Lenstip is the only review site I know of that checks for coma.
02-24-2014, 12:55 PM   #44
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QuoteOriginally posted by DeadJohn Quote
Let's use the FA 43 as an example. For astrophotography it's a dog because of too much coma distortion.
Amen to that.

Another (coma) dog: Sigma 20mm f/1.8 (for Nikon)
I had to send it back because of its significant coma.
Good little lens otherwise! :P

Michael
02-24-2014, 02:29 PM   #45
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I prefer to look at the lens reviews on this website you might know - Pentax Forums It even has a wonderful sample photo gallery!
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