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04-15-2011, 04:23 PM   #1
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I don't understand photozone.de

I was looking at the 50-135 on photozone. The MTF50 numbers were high numbers which I thought was a good thing. I don't know what they mean but I thought higher was better. But then I get to the verdict and it got 3.5 stars.

The DA70 got 4 and the FA77 got 3 and a half.

But what I don't understand is how the 50-135 only received 3.5 stars on optical quality but they were all very very close. Do I just value a half star more than the actual numbers. That half star to me seems worse than the numbers indicate.

04-15-2011, 05:04 PM   #2
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QuoteOriginally posted by justtakingpics Quote
I was looking at the 50-135 on photozone. The MTF50 numbers were high numbers which I thought was a good thing. I don't know what they mean but I thought higher was better. But then I get to the verdict and it got 3.5 stars.

The DA70 got 4 and the FA77 got 3 and a half.

But what I don't understand is how the 50-135 only received 3.5 stars on optical quality but they were all very very close. Do I just value a half star more than the actual numbers. That half star to me seems worse than the numbers indicate.
why do you need to pay attention to "stars", just pay attention to the actual test numbers and always compare those w/ other sites if that lens was also tested elsewhere - slrgear.com, lenstip.com, etc...
04-15-2011, 05:08 PM - 1 Like   #3
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A high optical score just means its a lens that has been very well corrected for aberrations, and has high resolution, and other optical merits.
Photozone does not take into account that some lenses are deliberately designed with aberrations to give a particular character to the lens, it just judges on optical performance.

For example, distilled water is technically perfect, Perrier is not, as it has high minerals dissolved in it. Yet you would prefer Perrier to distilled water.

Photozone is just one tool to decide on the lens choice. There are many other tools out there that consider other aspects. Its up to you to use the tools judiciously.
04-15-2011, 05:17 PM   #4
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QuoteOriginally posted by selar Quote
that some lenses are deliberately designed with aberrations to give a particular character to the lens
if you are talking about a regular zoom it is just nice way to say that there was some (or a lot of) cost saving, that's it...

04-15-2011, 06:58 PM   #5
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I find some of the reviews questionable if not unreliable, but that's my opinion.
04-15-2011, 08:20 PM   #6
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QuoteOriginally posted by deejjjaaaa Quote
if you are talking about a regular zoom it is just nice way to say that there was some (or a lot of) cost saving, that's it
No, I am talking about Limited primes, such as the FA77 limited and FA31 LTD that provide very pleasing results inspite of photozone's analysis.
04-15-2011, 09:20 PM   #7
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Photozone is also deliberately tough. They don't want all (or even very many) of their reviews to be "5 stars awesome lens" like what happens with so many products out there.

Photozone Rating System

I find it to be a refreshing change. Their reviews seem quite fair, which is really what matters I think.
04-15-2011, 09:37 PM - 1 Like   #8
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QuoteOriginally posted by selar Quote
No, I am talking about Limited primes, such as the FA77 limited and FA31 LTD that provide very pleasing results inspite of photozone's analysis.
Somebody said in a previous thread about Photozone that they are very into numbers, as seen in the MTF segments of the tests. While I openly admit to pouring over their data far too much to be healthy, I have to remind myself these have nothing to do with actually using the glass.

I can't explain why Photozone gives the DA* 50-135mm generally very good praise and then slap it with only 3.5 stars out of 5 for its optical quality, but then again they've given the same score to several Zeiss lenses, too. I understand that's a zoom versus a luxury prime; my point is that they don't seem to unfairly favor a particular brand, no matter what the reputation is. In the case of the FA 77 ltd. it's not necessarily that the lens had any particular failing, but instead it appears the lens performed in step with others in the same class. In other words, it was quite good, but it didn't stand out, either.

I really think any Photozone reader needs to be able to recognize the data that's most important to them. I've learned to pay close attention to the chromatic aberration figures, but I could not care less about vignetting. Those stars at the end of the articles have no impact on me, but I certainly take note when the reviewer mentions that a test needed to be canceled because of a manufacturing defect.

I should also mention that DxO Mark is another example of the whole stars vs. measurements vs. actual usage of a lens. The Sigma 17-50mm 2.8 HSM OS scored head-and-shoulders above the Tamron 17-50mm 2.8 as a landscape lens: 4.5 stars over Tamron's 3 stars. Yet, both lenses score admirably (and similarly) in terms of resolution, and the Sigma actually does worse when color fringing is considered. Granted, these are tests based on different camera bodies, but that only goes to show that their star ratings can't be the final word.

Pentax glass on DxO, generally, gets very low marks. But they were also tested on older bodies. Nikon, on the other hand, gets high numbers. But they are tested on newer models with higher resolution, newer anti-aliasing filters...

In the end, sometimes you simply need to listen to what others are saying based on experience and not worry about every measured figure.

04-15-2011, 09:51 PM   #9
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QuoteOriginally posted by justtakingpics Quote
The DA70 got 4 and the FA77 got 3 and a half.
So what? Instead of worrying how many stars, you should think about intended use of the lens i.e. film and digital bodies, or only digital bodies, form factor, what sort of photography you intend, whether the peak sharpness of the FA overrides the uniform but lower sharpness of the DA. If I was primarily to use for portraiture I would get the 77, if I wanted a compact general purpose tele, I would get the 70.
04-15-2011, 09:59 PM   #10
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QuoteOriginally posted by justtakingpics Quote
I was looking at the 50-135 on photozone. The MTF50 numbers were high numbers which I thought was a good thing. I don't know what they mean but I thought higher was better. But then I get to the verdict and it got 3.5 stars.

The DA70 got 4 and the FA77 got 3 and a half.

But what I don't understand is how the 50-135 only received 3.5 stars on optical quality but they were all very very close. Do I just value a half star more than the actual numbers. That half star to me seems worse than the numbers indicate.
A bit higher distortion, weaker resolution in borders at long end, higher chromatic aberrations - don't you think those are worth half a star less in optical performance? Note that on price/performance it scores like the DA 70 and is one half star ahead of the FA77. They also had issues with their first DA* sample and had to get a second one. Some photozone results may be arguable, but I don't think this is one of them.
04-16-2011, 12:28 AM   #11
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QuoteOriginally posted by Wheatfield Quote
I don't think even Photozone understands Photozone.
I gave up on that website when it became painfully apparent to me that his numbers didn't jive even remotely to what I observe in use often enough to make his results questionable.
I'm really beggining to think along the same lines....
04-16-2011, 06:17 AM   #12
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My opinion of Photozone is that it is a resource, one that gives a indication of a lens performance via a limited set of criteria, mtf performance matched to a certain camera. It is certainly not designed to be used as a "my brands fifty is better than your brands fifty" and some of the weightings of the points awarded are hazy at best. Zeiss glass for example generally seem to get very good scores across the board. Now it may well be that Zeiss glass are optically the best of the best with exceptional build quality, but they have only been measured on other brands cameras and so can in reality on be compared to those brands.
With regards to Pentax glass... excluding the DA* & zooms for a moment, our glass is expensive, our glass is by in large slow but our glass is also half the size of a typical competitor, made out of aluminium and paired with a K-5 can be used in bright sunlight to near enough pitch darkness handheld without any problems and deliver a sharp shot with fantastic contrast, rich colours and (read not artificial) a genuine recording of the scene we see. The criteria I mentioned in the previous sentence is very very difficult to measure, it is a combination of 3 factors, user ability, camera ability and lens ability, each is needed in equal amounts to get the maximum from each other. So Photozone is a resource, a valuable one but only a snapshot of what a lens is capable of. My 2c
04-16-2011, 07:31 AM - 1 Like   #13
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I think Photozone and other review sites are somewhat interesting, but it has been pretty seldom over the last 40 years of buying lenses that I have purchased a lens that wasn't better than I am, so I don't worry about it too much.
04-16-2011, 10:15 AM   #14
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QuoteOriginally posted by robbiec Quote
My opinion of Photozone is that it is a resource, one that gives a indication of a lens performance via a limited set of criteria, mtf performance matched to a certain camera. It is certainly not designed to be used as a "my brands fifty is better than your brands fifty" and some of the weightings of the points awarded are hazy at best. Zeiss glass for example generally seem to get very good scores across the board. Now it may well be that Zeiss glass are optically the best of the best with exceptional build quality, but they have only been measured on other brands cameras and so can in reality on be compared to those brands.
With regards to Pentax glass... excluding the DA* & zooms for a moment, our glass is expensive, our glass is by in large slow but our glass is also half the size of a typical competitor, made out of aluminium and paired with a K-5 can be used in bright sunlight to near enough pitch darkness handheld without any problems and deliver a sharp shot with fantastic contrast, rich colours and (read not artificial) a genuine recording of the scene we see. The criteria I mentioned in the previous sentence is very very difficult to measure, it is a combination of 3 factors, user ability, camera ability and lens ability, each is needed in equal amounts to get the maximum from each other. So Photozone is a resource, a valuable one but only a snapshot of what a lens is capable of. My 2c
.


This is how I use it, also. I think it's a good resource when used in conjunction with users reviews, other professional reviews and personal trials on your body of choice.


.
04-16-2011, 10:28 AM   #15
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QuoteOriginally posted by justtakingpics Quote
I was looking at the 50-135 on photozone. The MTF50 numbers were high numbers which I thought was a good thing. I don't know what they mean but I thought higher was better. But then I get to the verdict and it got 3.5 stars.

The DA70 got 4 and the FA77 got 3 and a half.

But what I don't understand is how the 50-135 only received 3.5 stars on optical quality but they were all very very close. Do I just value a half star more than the actual numbers. That half star to me seems worse than the numbers indicate.
I don't think you should be putting any stock in the photozone numbers. Some people here treat that site as if it is gospel on lens quality but even from the numbers you report, I would say they are WAY off. When I'm looking for a new lens I am looking at what the lens can actually do rather than wasting time with dumbass charts. Sorry, but I think they are a waste of time beyond a casual interest.

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