Photodo summary

G

Guest

As limited as the photodo ratings are, I find them interesting. One day boredom took over and I decided to copy the ratings into an Excel spreadsheet so that I could compare the values more easily. Here's the results (I hope I'm not violating any copyrights): <center><table border=1><tr><td>
Photodo in Excel
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(76.3 k)</td></tr></table></center>
 
G

Guest

I am not sure what all the ratings mean, it sure makes me feel good that many of our G CZ lens have the highest number. Thanks for your summarizing the info.

Howard
 
G

Guest

The grades are based on weighted MTF values (independently calculated by the folks who run the photodo site). I'm not sure exactly what they "really" mean either (in practical terms). Here's their explanation of the grades and the charts they provide:
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I provided this because people tend refer to this site and the site has no simple means of comparing the ratings of the various lenses. Also, because I found it interesting that the G lenses were, for the most part, at top of their respective categories (admittedly, I defined the categories, but I think they're reasonable).
 
G

Guest

Ron - Thanks for the spreadsheet I was planning planning on doing something like this in Access, and now that I have the data in electronic form, I probably will when I get a chance.

If you sort the sheet, you will see that our CZ lenses are some of the best in the world, beating out lenses that I alway thought were unbeatable.

Jim
 
G

Guest

Uh, the only MTF charts I've ever perused are from Zeiss for my Hassy. Correct me if I'm wrong, but aren't the Hasselblad 120mm Makro-Planar and the Rollei 120mm Makro-Planar THE EXACT SAME GLASS FOR THE EXACT SAME FORMAT? If so, why does Photodo rate them so differently? After examining their rankings for the Hassy lenses I own (and rent!) and use on a regular basis, then comparing their relative rankings with my experience, I have to conclude that their measurement methods are seriously flawed. Their rankings just don't match up with my chromes. Anyone else look critically at their charts?
 
G

Guest

I think soome of you are getting to caught up in the lens tests. Look at the results of your photography. Are your pictures sharp with good color and contrast? Are you satisfied with the results? If so, then just take the testing as a rough comparison to eliminate lenses that don't have the quality you need (want).

I have a friend who ran the old Modern Photograpy lens tests on every lens he bought. He would even return or sell lenses that did not meet his desired level of quality. Did it help? I don't think so, he is a talented photographer and would have won the awards anyway.

As for Chris' question, there are different ways to run the tests and there could be some differences for the ex&le you site. Also, you ned to k nnow how many individual ex&les of each lens was used in the test. The results are usually an average of many s&les. There are different ways of conducting the test. Read how the photodo tests were done and then try to find out how the Zeiss tests were done. I don't think any methods were flawed - you just have to compare apples to apples. So, looking critically at the charts is important, but so is looking at the way the tests were conducted

Your chromes tell it all - if they are the results you want, don't wory about the numbers.

Jim Slater
 
G

Guest

I only stated that I thought something must be wrong with the Photodo methodology because they had so widely disparate ratings for a Hassy lens and a Rollei lens which are, in fact, manfactured by Zeiss and use the exact same glass.

For the record, I agree with Mr. Slater--tests, schmests––follow your chromes. I like the out-of-focus characteristics and full-aperture sharpness of my Zeiss Hassy lenses; that's why I picked Hassy over others, notably Contax and Nikon.

Lastly, for anyone who's trying to wrap his/her brain around statistics (I was raised by statisticians), while the absolute number of random s&les, that is, lenses taken off the assembly line and tested, IS important, statistical averages are based on the variation, or lack thereof, BETWEEN these s&les. If 100,000 lenses are manufactured, 1,000 are tested, and the variance between them is less than, say, 2%, then you've got statistically accurate results. If the result is, say, 15%, you've got garbage, and 1) need to retest, and, 2) need to get more consistend manufacturing. ADDITIONALLY, LENS MANUFACTURERS WHICH DO ANYTHING OTHER THAN TEST ACTUAL PRODUCTION LENSES WHICH ARE PACKAGED FOR SALE TO CUSTOMERS (can you HEAR me, Canon L-series???) ARE DOING NO REAL TESTING AT ALL. Worse than that, some companies will publish MTF charts based only on their CAD (Computer Aided Design) plans for the lenses, without taking into account the manufacturing process. The difference between these MTF and reality is light-years.
 
G

Guest

I've also found widely varying results, on photodo, for lenses which conventional wisdom holds are optically identical - simply rebranded and given different exterior trim. It could be s&le variation, but you might also consider the coatings. HFT and *T are both supposed to be superb, but are they identical? I think coating differences can affect transmission and irradiation (light spread) in the glass. I agree you have to judge by your own results in real-world situations. The reason I resort to tests is that, prior to purchase, it's a way of evaluating for comparison to help make a decision. You need to add subjective reviews, as you find at photographyreview.com, although these aren't infallible, either - especially, I've found, with expensive items, where buyers seem to review under the influence of the myth surrounding certain brands and chime in to the chorus of "legendary, incomparable, etc." Still, how many of us can afford to buy all these items to test them?
 
G

Guest

2.7 for the Hassy/Zeiss T* 120mm Makro-Planar; 3.3 for the Rollei/Zeiss HFT 120mm Makro-Planar. Maximum range for testing appears to be 0-5. This is not a difference between coatings.

I agree with Mr. Stewart: there IS a definite aura around brands like Leica, Zeiss, and Hasselblad, but, then, there are also things like the M7, the Diascope 85 T*, and the 905 SWC to generate these kinds of ravings. Is everything with these brand names top-flight? Well, yes, but at what point does the law of diminishing returns set in?
 
G

Guest

Photodo has a page with links to various articles about various photographic subjects, including how their lens tests were done.

Click on the "articles" tab, then scroll down to "Equipment - lenses" and read the two articles "Understanding the MTF Graph" and "Understanding the MTF Graphs, numbers and grades." The second article explains how the tests are done. To compare photodo testng with testing done by others (especially the manufacturers), you need to know how the lens was tested and how the data was compiled and processed.

Almost any testing procedure can be weighted toward whatever the tester desires. Not all testing is fair - not all is valid. If there are no standards fot the testing, then anything goes. If all testing is done to a set of standards andc the data compiled and processed in the same manner, then tests done by multiple organizations can be compared.

It is entirely possible that the photodo tests were accomplished using a small population of lenses of any one given lens. It is possible that they tested only one lens and happened to get a bad one. At least they were all done byh the same person with the same equipment.

It is possible for variable results due to the testers using different test equipment and techniques. One lens could show different results from two different testers. And, a manufacturer will most always slant the tests for their own products to bring out the best features of those products.
 
G

Guest

A testing procedure which rates the two Zeiss 120mm lenses, one with Zeiss' T* coating and the other with Rollei's HFT coating, at 2.7 and 3.3 has serious flaws. I don't care what their methodology is; I've used both of these lenses and they perform exactly the same. Photodo is a write-off for me because of this discrepancy.
 
G

Guest

Chris,

I sorted throught the data from the spreadsheet and found other discrepancies on lenses (Leitz) that I know are better than rated. Could be poor data entry, or just poor data. Maybe the testing is not as good as it should be. However, remember that your own tests with the film that you use is the best test.

Jim
 
G

Guest

I'm not just saying that they're better than rated (I know from experience that the Zeiss 120mm Makro is wonderful with either the T* or HFT coating); I'm calling into question the difference beteen the two. IT'S NOT THAT MUCH, if anything. Everyone, believe what you choose to believe. If you want to believe that the Canon 200mm f/1.8 is a 4.8 and the Hasselblad 120mm Makro is a 2.7, go right ahead. See you in the funny pages!
 
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