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 Re: Yesterday's medium format digital backs | |
jcolwell wrote:
Hi Anders,
I\'d appreciate it if you would be more careful about how you quote me, and how you interpret the data I provided. I described how those resolution tests were made, using the USAF 1951 resolution test target, which has discrete step sizes between measurement values.
Your following quotation of my input implies that I think lens performance for different conditions with the same USAF 1951 resolution test values are the same. I never said this. The same quotation implies that I said the Planar 85/1.4 is every bit as sharp at f/4 as at f/8. I didn\'t say that. Also, I note that you linked to a comparison of Planar 85/1.4 ZE lens performance at f/4 and f/8, while I clearly stated that I tested a Planar 85/1.4 MMJ C/Y lens. Does this mean you think results for a ZE lens are the same as for a C/Y lens?
What I actually said about \"every bit as sharp\" was this, ...
... which has nothing to do with the Planar 85/1.4 MMJ USAF 1951 test results that I contributed, nor with the Planar 85/1.4 ZE comparison that you linked. Moreover, my comments on the 300mm lenses are not based on USAF 1951 test results, rather they were based on years of experience with both lenses, on a variety of cameras.
If you want to see how the A 300/2.8 APO compares to the EF 300/2.8L IS on a D800, then maybe you could do us all a favour by buying these items and then showing us how it should be done. Don\'t forget to tell us how you attached the EF 300/2.8L IS to the D800. 
Sincerely,
Jim
Hi Jim,
You are right that I made some mistakes when linking some of your earlier comments to the numbers presented.
Still I think that your measurement results show anomalies that are sure signs that they are not accurate.
I did not think the 85 MMJ and ZF are the same lenses. I found the Planar 85 ZF as the closest, to illustrate the universal behaviour that high quality lenses with maximum aprture f/1.4 lose visible MTF at f/8 compared to f/4. I checked about 15 lenses for that, and they all do it. The amount varies, between about 5% and 8% (going by PZ numbers).
Regarding discrete steps, a difference of 5% from 71 is 67 or 74. It should show up in your numbers.
The 300 2.8 L IS on the D800, now that is funny. Now you are distorting my words out of meaning as well
First, I mentioned both the D800 and the NEX 7. Second, I want alternatives to the 300 2.8 L IS precisely because it cannot be mountd on Nikon. If it could, I would just use it and not even think about the Mamiya. On top of, that, I cannot just go out and buy a 645 300 2.8 APO. One of the curses with alternative lenses, they are hard to find, many sellers don\'t ship to Norway (yes, as the only country, I don\'t know why), and you take a risk at what you get.
The technical points in my criticism of your measurements stand on their own, and they do not imply anything further than just what they are.
Hope to see you soon,
Anders
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