Some new lenses


Mike-P

Link Posted 04/07/2011 - 22:37
I am not a PU Plus member but can see both reviews.
No equipment list here but thanks for taking an interest. My Flickr

johnriley

Link Posted 04/07/2011 - 22:40
Then the only thing I can think of suggesting is to log out and log back in again.

Otherwise, a report to IT and I'm sure they will be able to help.
Best regards, John

johnriley

Link Posted 05/07/2011 - 13:42
The first set of questions regarding comparisons now have some answers as the 35mm f2.4 review is now up on EPZ:

http://www.ephotozine.com/article/smc-pentax-da-35mm-f-2-4-al-lens-review-16804

No doubt a link on PU will follow soon.
Best regards, John

rparmar

Link Posted 05/07/2011 - 14:04
I have a small criticism. You write: "There is no aperture ring, which in one way is a pity as it is evident that this lens is actually a full frame design and could be used with Pentax film cameras." Firstly, this is a confusing sentence and secondly, it implies something incorrect, that the lack of the dial demonstrates the lens covers the full frame. I am sure you mean something different!

As for the lens itself, surely this must be the first time MTF scores are higher at the borders than in the centre of an image? What an odd result!
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johnwhit

Link Posted 05/07/2011 - 14:12
rparmar wrote:

As for the lens itself, surely this must be the first time MTF scores are higher at the borders than in the centre of an image? What an odd result!

I've seen the same with the Chasseur d'Image (French Publication) test of the FA-135/2.8, but they really liked the lens.




If this infringes any copyright please remove it

John
PPG link

In LBA hiatus.
Last Edited by johnwhit on 05/07/2011 - 14:16

johnriley

Link Posted 05/07/2011 - 14:16
The sentence reads OK to me, simply saying that it's a pity there's no aperture ring as then we could take more advantage of its full frame coverage, should we wish to.

As for the graphs, they exhibit the normal rise and fall pattern of a high quality lens. You are maybe reading the third (CA) graph in reverse, where the higher the result the more CA is present. Needless to say, the centre shows much lower (better) results than the corners.
Best regards, John

rparmar

Link Posted 05/07/2011 - 14:28
Let me clarify. The sentence does not say why it is evident the lens is full-frame. That is one claim. The second claim has to do with the aperture ring. Eliding the two in one sentence is indeed confusing, even to me -- and I know what you mean!

And no, I did in fact mean the MTF curves, not the CA graph. Look again and it is clear the corners have higher bars than the centre, for all the wider apertures, anyway.
Listen to my albums free on BandCamp. Or visit my main website for links to photography, etc.

johnriley

Link Posted 05/07/2011 - 14:45
As regards the MTF curves, they are what they are and it's not unknown.

Another example is the Voigtlander 50mm f1.8 Ultron of the 1970s, where the edges were corrected more than the centre.

However, the upshot is for the 35mm f2.4 that it's an excellent lens, tremendous value for money and although it's not as good as the 31mm it's more than good enough for critical use.
Best regards, John

Don

Link Posted 05/07/2011 - 14:59
johnriley wrote:
As regards the MTF curves, they are what they are and it's not unknown.

Another example is the Voigtlander 50mm f1.8 Ultron of the 1970s, where the edges were corrected more than the centre.

However, the upshot is for the 35mm f2.4 that it's an excellent lens, tremendous value for money and although it's not as good as the 31mm it's more than good enough for critical use.

because I run several systems of cameras, including Pentax d-slrs, Sony camcorders, and go-pro, and I have to run audio gear from Peavy, Bose, Rode, Sony, Audio Technica...

to create our multimedia projects (not to mention all the Apple systems and software)...
COST is always an issue for us when buying gear. We simply do not pull in enough money to justify the lenses JR has just acquired. I wish every company we deal with had the kind of bang for the buck, outstanding value as Pentax is offering with the 35 2.4. And the KR.
Fired many shots. Didn't kill anything.
Last Edited by Don on 05/07/2011 - 14:59

Algernon

Link Posted 05/07/2011 - 15:04
I've got a Tamron AF 28-90mm that I bought about the same time as a Pentax Z1-P It hadn't any aperture scale or distance markings so they were not needed on the later film cameras.

The MTF figures do look very odd. Could it be a focus error?
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi

johnriley

Link Posted 05/07/2011 - 15:10
No, there's a star focus point on the chart and focus is done very carefully. In addition, the chart is absolutely huge so there's no real issue with working distance.

Just accept it is what it is - the computer does the chart automatically. Magic, it has to watched doing it to be believed. The thing about scientific results is that we accept our observations, rather than not accepting them if they don't fit a preconceived idea.
Best regards, John

johnwhit

Link Posted 05/07/2011 - 15:11
Algernon wrote:

The MTF figures do look very odd. Could it be a focus error?

The centre is sharper from f/4 onwards.

John
PPG link

In LBA hiatus.
Last Edited by johnwhit on 05/07/2011 - 15:11

johnriley

Link Posted 05/07/2011 - 15:17
Yes indeed. I've just speculated on EPZ (potentially very confusing having this conversation split over two areas!) that perhaps the AL component is to blame, if blame is the correct term for something that clearly has evened out the performance so well across the field.
Best regards, John

Algernon

Link Posted 05/07/2011 - 15:26
The Photozone test shows Excellent in the centre for all
apertures...... I still think it's a focus error? DOF would
compensate at f/4 onwards link

Edit:
Also Excellent on this test link
Half Man... Half Pentax ... Half Cucumber

Pentax K-1 + K-5 and some other stuff

Algi
Last Edited by Algernon on 05/07/2011 - 15:28

johnriley

Link Posted 05/07/2011 - 15:34
Unfortunately they are all different lens samples as well as different testers - a direct comparison can never be made. However, comparisions can be made between different lenses tested by the same tester, provided of course that the testing situation has not changed.

I would point out that as focusing is done on the centre of the chart, if anything this would favour a high performance at centre. If there was a focus error this would mean that the edges were even more creditable.

What is possible is some curvature of field, but that is not covered in the testing regime.
Best regards, John
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