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11-29-2012, 08:12 PM - 1 Like   #31
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QuoteOriginally posted by lytrytyr Quote
Klaus' tests on the K5 do indicate that at f/8,
the kit zoom between 28 and 55mm
resolves the borders better than the FA43.
I'm skeptical about the accuracy of these tests. They often don't match my own experience with the lenses involved, nor are they consistent with tests done by other sites. Worse, the divergences between tests from varying sites is too widespread and too great to be plausibly explained by sample variation. In any case, I no longer trust numerical tests of lenses. They're probably not all that accurate, and even if they were, it's questionable whether they are all that significant. At the end of the day, it's what the images produced by a given lens appear to the naked eye, rather than how a lens fares on numerical evaluations, that is important. If I'm researching a lens, I'll put far more weight on images I see, particularly full resolution images, than numerical tests. But in the end, the only way for me to evaluate a lens is to use in the field, trying to get the best images I possibly can out of it. That's the only way I know of reliably testing a lens.

11-29-2012, 08:30 PM   #32
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If you ignore the stars, PZ tests are quite useful.
11-29-2012, 09:35 PM   #33
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I dont like Photozone and their reviews. The way they come to their lens "conclusions" is puzzleling and they come across very biased.
11-30-2012, 12:38 AM   #34
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QuoteOriginally posted by Blue Quote
May is the operative word because he may not have compensated.
This is the issue that was raised in the earlier post

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/206591-photozo...ml#post2185102

11-30-2012, 12:56 AM   #35
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QuoteOriginally posted by northcoastgreg Quote
I'm skeptical about the accuracy of these tests. They often don't match my own experience with the lenses involved, nor are they consistent with tests done by other sites. Worse, the divergences between tests from varying sites is too widespread and too great to be plausibly explained by sample variation.
Optyczne/Lenstip reaches a similar conclusion about the FA 43 on the K5,
so I do not think that Photozone's test is an outlier.

QuoteOriginally posted by northcoastgreg Quote
In any case, I no longer trust numerical tests of lenses. They're probably not all that accurate
Error margins are specifically addressed on the page
Photozone Lens Test FAQ

QuoteOriginally posted by northcoastgreg Quote
and even if they were, it's questionable whether they are all that significant. At the end of the day, it's what the images produced by a given lens appear to the naked eye, rather than how a lens fares on numerical evaluations, that is important.
Photography is both art and science.
Understanding the physical limitations of the tools
is a key part of the subject
if you wish to explore it fully.

QuoteOriginally posted by northcoastgreg Quote
If I'm researching a lens, I'll put far more weight on images I see, particularly full resolution images, than numerical tests.
The limitations of that came up in the earlier post
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/206591-photozo...ml#post2185067

QuoteOriginally posted by northcoastgreg Quote
But in the end, the only way for me to evaluate a lens is to use in the field, trying to get the best images I possibly can out of it. That's the only way I know of reliably testing a lens.
That doesn't help a person who is contemplating a major purchase,
and who doesn't have access to a lens (e.g. by rental or in a store).

The test sites, for all their drawbacks, are very helpful in that situation.
12-01-2012, 06:46 AM   #36
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I have not seen any meaningful measurement, that would really contradict PZ's measurements. I find the way, Klaus explains the measurements and his conclusions very easy to follow. Ofcourse every reader needs to balance the different values against each other. I personally look at center sharpness and contrast and don't care too much about colour fringing (unless it is really serious) or sharpness fall-off towards the edges. Everybody needs to find his own most important aspects.

Photozone's and other site's finding provide onhly a basis - everybody needs to rethink the meaning, rebalance what is more or less important for him and draw his own conclusions.

Measurements are not meant to replace thinking.

Also, different results at different sites hint at what photographoic magazines (at least in Germany) have been pointing out for a very long time now: Pentax quality controle is lax. I have rarely seen a Nikon lens which has as much decentering, than many Pentax lenses show in those reviews. The lenses Pentax rebranded from Tamron support this: in almost all reveiws of the older Tamrons (even the 28-200 of old days) the Tamron showed better performance, than the Pentax branded, because the Pentax lens was much more decentered.

I personally think, this is the case, because Pentax always was focused on the Japanese home market, where the best sharpness was not always asked for, but other virtues seemed to be more important. Of course I cannot support my opinon with any kind of objective measurements.

Ben
12-01-2012, 07:24 AM   #37
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QuoteOriginally posted by Ben_Edict Quote
I have not seen any meaningful measurement, that would really contradict PZ's measurements. I find the way, Klaus explains the measurements and his conclusions very easy to follow. Ofcourse every reader needs to balance the different values against each other. I personally look at center sharpness and contrast and don't care too much about colour fringing (unless it is really serious) or sharpness fall-off towards the edges. Everybody needs to find his own most important aspects.

Photozone's and other site's finding provide onhly a basis - everybody needs to rethink the meaning, rebalance what is more or less important for him and draw his own conclusions.

Measurements are not meant to replace thinking.

Also, different results at different sites hint at what photographoic magazines (at least in Germany) have been pointing out for a very long time now: Pentax quality controle is lax. I have rarely seen a Nikon lens which has as much decentering, than many Pentax lenses show in those reviews. The lenses Pentax rebranded from Tamron support this: in almost all reveiws of the older Tamrons (even the 28-200 of old days) the Tamron showed better performance, than the Pentax branded, because the Pentax lens was much more decentered.

I personally think, this is the case, because Pentax always was focused on the Japanese home market, where the best sharpness was not always asked for, but other virtues seemed to be more important. Of course I cannot support my opinon with any kind of objective measurements.

Ben
I look at the PZ charts and interpret them myself and just look at the summary and stars subjectively. I do the same thing with other sites.
12-01-2012, 08:30 AM   #38
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I could be wrong, but as I understand things... until early 2011, the various lens tests were performed on an all original K10D, then tests were moved to a customized K-5 with the AA filter removed. Test lenses are provided by friends and once the results are in they were returned. As such, the results may be accurate for a particular lens/camera pairing at one point in time, but so what? Given the rapid changes in the DSLR scene (component design advances, firmware upgrades, software drivers, etc), plus sketchy provenance for the subject lens/camera body, as time moves on, test results rapidly lose their relevance to today...

My rule-of-thumb is to give more weight to a lens test for a subject paired to a camera body most similar to mine. Unless they are close, I appreciate the effort, but consider the results... well... just, meh ...

My two cents...M


Last edited by Michaelina2; 12-01-2012 at 09:04 AM.
12-01-2012, 08:35 AM   #39
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QuoteOriginally posted by Blue Quote
It doesn't help that Photozone heaps praise on the DA 70 Ltd
I personally am a champion of the DA 70 and don't appreciate the implication of your statement that it is obviously inferior and as such is an example of the injustices by PZ towards the FA line. I expect from some of the testimonial on this forum any day to hear that all the FA lenses have ascended to heaven and taken their rightful place on angel cameras. While the DA line on the other hand has in shame marched to the sea and leapt in where they too belong. I use old lenses and new lenses for various reasons but I do not believe for a second that a photo I took would have been made magically incredible had I used an FA lens to take it.
12-01-2012, 08:58 AM   #40
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QuoteOriginally posted by Michaelina2 Quote
I could be wrong, but as I understand... until early 2011, the various lens tests were performed on an all original K10D, then tests were moved to a customized K-5 with the AA filter removed. Test lenses are provided by friends and once the results are in they were returned. As such, the results may be accurate for a particular lens/camera pairing at one point in time, but so what? Given the rapid changes in the DSLR scene (component design advances, firmware upgrades, software drivers, etc), plus sketchy provenance for the subject lens/camera body, as time moves on, test results rapidly lose their relevance to today...

My rule-of-thumb is to give more weight to a lens test for a subject paired to a camera body most similar to mine. Unless they are close, I appreciate the effort, but consider the results... well... just, meh ...

My two cents...M
This is what basically any reviewer does. You can always only compare lens tests taken with cameras with the same or very similar sensors. Except if you get an independtly done MTF measurement. But that is more or less useless for the world of real photography, because even with a MTF measurement the results are fairly dependent on the equipment and workflow - which means, that you also can only compare MTF results made in the same lab with the same setup.

So, your personal way of appreciating tests critically is the right way to go, I think.
Ben
12-01-2012, 09:25 AM   #41
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You have to realize #1 that this site is a great service to the Pentax community. Lets not got bogged down in the criticism.

Second and perhaps the biggest point, as pointed out before... his results are meaningful at the distance from the test chart the camera was when he took them on a 2d test chart.

If you shoot at any other distance and at a 3D image instead of 2D then your results may vary.

Many of Pentax's best lenses were designed to achieve center sharpness. SO the worst example being the 18-135, which has excellent centre sharpness in 13 of the 18 measured settings but is rated at 1.5 stars. Other lenses that have one or 2 excellent centres but have better border ratings are rated 2 and 3 stars. This is a choice that has been made by klaus to reward stars based on higher average setting as opposed to reward it for areas of excellence. The 18-135 may be the best 24 mm lens available for a K-mount right now. But because it's a zoom it's rated across it's range, not where you're likely to use it. I'm guessing in the case of the 18-135 the CA numbers and vignetting also have something to do with it's low rating, but as I said, because of it's characteristic I can use it. There are many higher rated lenses in terms of stars that I couldn't use.

In the end, I think the best course of action is to test the lenses you like against Klaus numbers to see what they mean. I actually think they mean quite a lot. If you look at the actual numbers and test... you would predict that images shot with the kit lens will never be better than those shot with the 18-135. That's what we've found over time, to the point we no longer use our kit lenses. Other comparisons have been bang on with some exceptions.

We tested the DA 18-135, DA* 60-250, Tamron 90 macro and Sigma 70-300, all at 90 mm on landscape @infinity.
The Tamron and 60-250 were judged best images in that order. What surprised us was how close the 70-300 was. The 18-135, used on landscape at that focal length was of course a disaster. The border weakness was noticeable. But what that told me, was that you have to rate a lens on what it can do for you. Not on it's average MTF numbers. The 70-300 may be weak in it's long end. But 70-150, it's a competent lens.

Having these numbers in no way excuses you from doing the research to understand what a lens is good for.

My 18-135 is excellent from 22-50 (but be prepared to have CA ruin a shot from time to time)
My SIgma 70-300 is very good from 70-150.
Klaus's numbers will tell you that.

What they won't tell you is why the Tamron 90 is better than the 60-250. For that you have to get into things like colour tint and contrast etc. which klaus doesn't even begin to address. The DA *60-250 and Tamron 90 images are very similar, but the Tammy's images just have a bit more definition based on colour contrast, and sparkle, whatever sparkle is.

Last edited by normhead; 12-01-2012 at 09:33 AM.
12-01-2012, 11:11 AM   #42
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QuoteOriginally posted by Schmidlapper Quote
I personally am a champion of the DA 70 and don't appreciate the implication of your statement that it is obviously inferior and as such is an example of the injustices by PZ towards the FA line. I expect from some of the testimonial on this forum any day to hear that all the FA lenses have ascended to heaven and taken their rightful place on angel cameras. While the DA line on the other hand has in shame marched to the sea and leapt in where they too belong. I use old lenses and new lenses for various reasons but I do not believe for a second that a photo I took would have been made magically incredible had I used an FA lens to take it.
First off, you need to realize that you just quoted a very small part of my post and took it way out of context. No where did I say the DA 70 ltd was inferior or that the FA 77 would automatically be better. There are several threads where I have discussed both lenses and discussed both lenses strengths, weaknesses and each's greatest attributes. If you misconstrue what I say, you are doing it when I am doing like you and champion the FA 77. Generally, many feel the need to "tear down" the FA 77 when discussing the DA 70. If you wold go look at my profile, you would see that I currently have a DA 15 ltd, DA 21 ltd, DA 35 LTD, and FA 77 ltd. I used to have the DA 40mm. That hardly indicates a FA ltd bias that you are suggesting here.

Here is my complete post with the pertinent part highlighted. In no way did I bash the 70. All I said was that I think PZ shows DA ltd bias relative to the FA ltd line.

QuoteQuote:
While the Photozone crew aren't a conspiracy, there are plenty of Pentax bashers that like to use the mtf data from them to criticize Pentax lenses. The FA Ltd series is particularly hammered in numerous threads here at PF alone. It doesn't help that Photozone heaps praise on the DA 70 Ltd and is critical of the FA 77 Ltd. This is in part because of the torture test the FA 77 was subjected to but the 70 was not. In addition, the designer stated in a scientific publication that the design of the FA ltd lens wasn't done in a way to optimize mtf on a flat surface.

Last edited by Blue; 12-01-2012 at 11:17 AM.
12-01-2012, 11:31 AM   #43
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QuoteOriginally posted by Blue Quote
First off, you need to realize that you just quoted a very small part of my post and took it way out of context. No where did I say the DA 70 ltd was inferior or that the FA 77 would automatically be better. There are several threads where I have discussed both lenses and discussed both lenses strengths, weaknesses and each's greatest attributes. If you misconstrue what I say, you are doing it when I am doing like you and champion the FA 77. Generally, many feel the need to "tear down" the FA 77 when discussing the DA 70. If you wold go look at my profile, you would see that I currently have a DA 15 ltd, DA 21 ltd, DA 35 LTD, and FA 77 ltd. I used to have the DA 40mm. That hardly indicates a FA ltd bias that you are suggesting here.

Here is my complete post with the pertinent part highlighted. In no way did I bash the 70. All I said was that I think PZ shows DA ltd bias relative to the FA ltd line.
The issue with Photozone is that Klaus takes into account pricing when awarding stars. A crappy lens sold for 100 dollars is given better stars than a much better lens sold for 900 dollars. I am not really in favor of grading things this way, because it tends to make the system confusing. Basically, Klaus believes that many of Pentax's lenses are expensive for what they are. Particularly some of the DA primes, which have relatively slow apertures, just have don't quite measure up.

With regard to the FA 77 versus DA 70, I would choose the FA 77 every time, but it is actually pretty close. The FA 77 is quite prone to purple fringing, which the DA 70 really isn't (no torture test about it, I shot them both the same way and it pops up frequently with the FA 77 and didn't with my DA 70). It is easy to fix in lightroom and not that big a deal. It also doesn't focus nearly as fast as the DA 70 did. Still, I like the wider aperture and the bokeh is nicer on the FA 77, so that is my opinion. 4 stars for the FA 77 and 3.75 for the DA 70.
12-01-2012, 11:37 AM   #44
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In the Photozone numbers there are very few lenses in existence that can match the numbers posted by the 77 ltd @5.6. at least at 10MP. If you're a guy like me, looking for peak performance in every exposure, the 77 is a no brainer. I've seen nothing in the images, of which there are tons, in the 77 thread to dispute that. The 70 is an excellent lens as well. There's no reason to feel it's less because the 77 might be better. The only reason I won't buy a 70 is, I thought I'd buy the 35 2.4 to last until I could afford a 31 ltd. I like the 35 2.4 so much I've taken the 31 ltd off my list. If I buy the 70 I know that's going to happen to the 77. And for this focal length, I really want that F1.8. So I'm not going to tempt myself to pass it over. When I come to make an absolute decision between these two lenses it will comedown to colour contrast and colour cast, which lens has the pixie dust. If everything else were a tie, then I'd go with the 77 for the faster aperture.

Now if only there were a 24 1.8
12-02-2012, 03:22 PM   #45
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Why worry about the reviews so much? They're a good resource in finding information about lenses but they're not the final word. It's up to the person reading the review to look at the information and decide which lens they want to buy. I know that I personally have had good luck buying lenses based off tests like Photozone's, but ultimately I decide based on my preferences and what the reviews say about a lens and how it meets my preferences.
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