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03-06-2013, 11:35 PM   #226
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QuoteOriginally posted by Ole Quote
Obtaining 100% accurate focus is an impossibility by manual focusing a K-5 IIs so I resorted to relying on CDAF. So that's what you got and perhaps that's why F11 may look sharper than F8?

Eliminating any and all vibrations during the shot was very hard with this long bastard of a lens. If someone donates a much studier tripod than the one I've got (Manfrotto 458B) I'll reshoot The F*250-600 actually was more stable on the tripod (it also weighs more).

I was also baffled by the lack of moire, I can only chalk it down to lack of resolution due to either inaccurate focus of vibrations.
Regarding manual focus or soft images......It took a number of outings before I had any keepers from the A*600 or A*1200 but that was more from vibration and technique. Ironically, panning or action shots dampens the vibrations whereas manually using the shutter release button leaves the view shaking sometimes for many seconds. The 560 should be the same......there is going to be a period requiring some time getting used to the lens......but it should be the same as any lens (Pentax / Nikon / Canon).

I hope the mount point is balanced...the A*600 is not but the A*1200 is perfectly balanced and is weightless when using on a Gimbal.

03-06-2013, 11:57 PM   #227
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QuoteOriginally posted by rvannatta Quote
Perhaps you could confirm an observation that I think I have made with respect to long lenses and DOF. Specifically, I have spent some
time comparing the results of a couple Pentax exotics that I happen to own--- an FA*600 f/4 and an A*400 f/2.8 and a pentax dedicated
TC's.-- the 2x-L and the 1.4x-L sometimes stacked with another converter...

Answers I've been fishing for include whether Optical cropping (adding a TC) produced better results than Digital Cropping (cropping in Photoshop). One of the casual observations that I have made however. is that adding a TC to a lens doesn't seem to alter
the DOF characteristics of the lens, Thus if you were fairly close (lens to subject) where DOF could become an issue you could
use the A*400 with a mild TC (the 1.4x-L) --- and get the effective focal length of almost 600---- actually 560, but the DOF associated
with a 400mm lens instead of the longer focal length glass.

Guess I'm looking for some validation of what I think I've observed... but anyhow my present thinking is that the 400mm with a TC
is a pretty good gambit where DOF (or lack thereof) is going to be the spoiler of a photo. Or am I keeping my A*400 f/2.8 around
even though it has no chance of out performing the FA*600 f/4 no matter what the conditions....
The DOF of a 400mm f/2.8 with a 1.4TC would be the same as a 560mm f/4... i.e. the TC isn't a magic DOF extender. The DOF actually gets a bit smaller IIRC.
03-07-2013, 01:35 AM - 1 Like   #228
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QuoteOriginally posted by ElJamoquio Quote
I post-process my images, so the fact that the K-5 is pre-cropped isn't in-and-of-itself an advantage for me.
Except that you end up with more pixels on the K-5's pictures than if you crop the D600 to the same FoV. This doesn't apply to the D800 though (but does when the K-3s is out).
03-07-2013, 09:14 AM   #229
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QuoteOriginally posted by falconeye Quote
[...] As a matter of fact, only very few people ever mastered the art to do a proper tele lens test. [...]
I do not want to question a proper test, which should be performed - if possible.

However, normally nobody carries a concrete block as tripod. Focus bracketing and the usage of flash both also seem to be less common in tele photography.

So, how much of the measured resolution is actually preserved in wildlife shots with ultratele lenses? Or in an exaggerated way: To which amount do higher MTF values for extreme tele lenses really guarantee better image quality? The test shots of the DA 560 and FA* 250-600 both seem to be limited by technique rather than by optical performance.

03-07-2013, 09:17 AM   #230
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QuoteOriginally posted by froeschle Quote
I do not want to question a proper test, which should be performed - if possible.

However, normally nobody carries a concrete block as tripod. Focus bracketing and the usage of flash both also seem to be less common in tele photography.

So, how much of the measured resolution is actually preserved in wildlife shots with ultratele lenses? Or in an exaggerated way: To which amount do higher MTF values for extreme tele lenses really guarantee better image quality? The test shots of the DA 560 and FA* 250-600 both seem to be limited by technique rather than by optical performance.
I suppose a concrete block could be supplanted by one of those super serious solid tripods that I see going for several thousands of dollars. I do remember reading a few threads where users of super telephotos put a ton of effort into stabilizing their telephotos to shoot with.
03-07-2013, 03:53 PM   #231
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If test require nailing camera lenses to breeze blocks to minimise vibration I don't see the point of the test? If I can't use it on a manageable tripod it has no value.
03-07-2013, 04:00 PM   #232
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I don't think the question is necessarily "it's not practical to shoot with a cinder block mounted to your lens!"

The question is - the vibrations affecting these super telephotos are not consistent from user to user, or from situation to situation. How can you compare the lenses if one lens gets more vibration due to some random factor than the other lens? In other words, I sincerely doubt we can ensure that any test that includes vibrations can keep all the vibrations equal.

By using the strict method that Falc listed, at least we'll know which lens is sharper - even if you never achieve that sharpness in field. It's not about the raw numbers, but about the numbers in comparison to each other.
03-07-2013, 04:12 PM   #233
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QuoteOriginally posted by PeterBex Quote
If test require nailing camera lenses to breeze blocks to minimise vibration I don't see the point of the test? If I can't use it on a manageable tripod it has no value.
The point is to determine the ultimate performance of the lens by eliminating as many external sources of blur or softness as possible.

03-07-2013, 06:52 PM   #234
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QuoteOriginally posted by froeschle Quote
However, normally nobody carries a concrete block as tripod. Focus bracketing and the usage of flash both also seem to be less common in tele photography.
...
seem to be limited by technique rather than by optical performance.
I hoped the question would be raised, esp. to motivate Adam and Ole to accept the effort required.
QuoteOriginally posted by JinDesu Quote
By using the strict method that Falk listed, at least we'll know which lens is sharper
That's part of the answer. A test must not provide arbitrary results.

Another part is that some of the issues can be avoided in the field, but create serious problems in a controlled test. E.g., in the field, you can shoot free hand or with a bean bag and at high enough iso to avoid shake and vibrations (vibrations are almost eliminated by hand holding). And a focus bracket can often be replaced by tacking a series of shots. All of this is unavailable within the context of a controlled test.

And as has been said, all sources of blur add up, so it matters to keep them all small which includes lens aberrations.

Btw, a bean bag doesn't eliminate shutter blur which is why I'd go for flash or the block of concrete when doing an MTF test. Again, in the field, shutter blur is avoded by the typically short exposure time.

Last edited by falconeye; 03-07-2013 at 07:02 PM.
03-07-2013, 08:08 PM   #235
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QuoteOriginally posted by gazonk Quote
Except that you end up with more pixels on the K-5's pictures than if you crop the D600 to the same FoV. This doesn't apply to the D800 though (but does when the K-3s is out).
Of course... on APS-C type cropping the D600 is down to 10MP. For me that's enough 99% of the time. For the other 1%... if I have to crop that much, the picture isn't going to be good enough to print big enough to put it in the 1%.
03-07-2013, 11:10 PM   #236
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QuoteOriginally posted by falconeye Quote
Another part is that some of the issues can be avoided in the field
...however there are some that can't be avoided. Shooting with a long focal lens means you are likely to target objects a long distance away and then you will encounter atmospheric conditions i.e. heat shimmer and other conditions which will vary from day to day.

Nothing is ever perfect, is it.
03-08-2013, 02:02 AM - 1 Like   #237
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Maybe I am alone in this but I don't want or need examples of flat items shot in a controlled situation. By now I would have expected to see more real-life shots of different subjects, under different lighting conditions. Such shots are much more informative to me as most people never shoot images of flat items with test patterns on them. Of course, This is not to say that it isn't good and infomative to subject the lens to intensive scientific testing, but I think such tests should only be the last step done.

If the lens was offered to me for testing I would already have flooded the web with many technically correct shots, enough to get an idea of the lens' performance. (I have experience with both the Sigma 500mm f/4.5 APO EX and the SMC Pentax-F* 250-600mm f/5.6; the same lens that Adam owns). I don't say this to brag, just that I'm disappointed by the number of available real world examples. It's not that hard to just go outside, drive off with the car and get some random shots?

Keep up the good work, Adam and Ole, but please don't forget to use the lens the way it was intended for
03-08-2013, 06:29 AM   #238
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+1 with Asahiflex
03-08-2013, 07:05 AM - 2 Likes   #239
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Actually that point raises the 'Pentax" question. If Pentax was building lenses to reproduce images in 2 d a few feet away from the camera would they build them the same way?

Does a lens that produces the best images in a test chart, produce the best images in the field? Until that question is answered, test charts are essenitally meaningless.

Images like this one, taken on windy days, my tripod was shaking and the leaves on the trees were blowing... and I really like the sereis of pictures. With all due respect, advice like "use flash" is pretty meaningless out in the world.

I would argue, the way the lens renders the image is more important than sharpness, though sharpness may be a component. It has to be combined with other elements. One component of photographic style, both portrait and landscape could be to use softer lenses that handle out of focus areas better, as opposed to great sharpness.

Having said that I'm going to go looking for that great array of fantastic d800 images, there should be a pile by now with all the great photographers jumping on that band wagon. Sites like Luminous Landscape should be dominated by D800 images if resolution is the be all and end all. But it isn't. Not even close.

go to this web site...

http://www.photoextract.com/art-photography
Not one D800 image on the first page... where is the D800 advantage?


Last edited by normhead; 03-08-2013 at 07:19 AM.
03-08-2013, 07:17 AM   #240
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QuoteOriginally posted by normhead Quote
Actually that point raises the 'Pentax" question. If Pentax was building lenses to reproduce images in 2 d a few feet away from the camera would they build them the same way?

Does a lens that produces the best images in a test chart, produce the best images in the field? Until that question is answered, test charts are essenitally meaningless.

Images like this one, taken on windy days, my tripod was shaking and the leaves on the trees were blowing... and I really like the sereis of pictures. With all due respect, advice like "use flash" is pretty meaningless out in the world.
I agree 100% with this. I understand the urge to scientifically measure and test things, but in the end this will only prove how this lens performs on a test chart 6 metres away, when using a flash.
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