TEST SHOTS for LENS EVALUATION

[gkopeliadis]

I think that the test shots posted here for lens evaluation are totaly useless unless they are 100% size / crops.
All lens are the same (more or less) on a 1024X768 photograph, let alone smaller.
Please note that I'm writing about lens evaluation, not photographer
What is your opinion on that?
Edited

[BBear]

i am confused by the language used: "I think that the test shots posted here for lens evaluation are totaly useless they are 100% size / crops."


I am not sure if you are saying test shots should be posted at 100% crops or if they should be posted at full resolution (though the forum will resize it).


Can you clarify?


And maybe to help out people that are still confused about 100% crops and what not, could you post a picture in both scenarios?


Thanks!

[rburgoss]

I do not consider some test shots to be useless. Lens comparisons when done under the same conditions and presented under the same conditions can do show the differences whoever did the test is trying to demonstrate.

Evaluations in contrast, sharpness, flare, chromatic aberrations, distortion or whatever detail wants to be tested and compared, can be easily evaluated "on screen", considering that such evaluation is seen on a side by side mode and of course, on the same screen.

Robert B

[tomtor]

Originally Posted by rburgoss

I do not consider some test shots to be useless. Lens comparisons when done under the same conditions and presented under the same conditions can do show the differences whoever did the test is trying to demonstrate.

Evaluations in contrast, sharpness, flare, chromatic aberrations, distortion or whatever detail wants to be tested and compared, can be easily evaluated "on screen", considering that such evaluation is seen on a side by side mode and of course, on the same screen.

Robert B

Exactly, you can already see much from a resized image, except pixel level sharpness.

That's why a good test should show 100% crops AND a resized image (allthough a reference to full size images could be used for both purposes).

[Wheatfield]

Originally Posted by gkopeliadis

I think that the test shots posted here for lens evaluation are totaly useless they are 100% size / crops.
All lens are the same (more or less) on a 1024X768 photograph, let alone smaller.
Please note that I'm writing about lens evaluation, not photographer
What is your opinion on that?

Personally, I am in complete agreement, not that what I think really matters. Any thread with the subject line "Proof that the &^%$* lens doesn't suck" (or similar) is almost guaranteed to be a useless waste of bandwidth.

[Lowell Goudge]

Originally Posted by gkopeliadis

I think that the test shots posted here for lens evaluation are totaly useless they are 100% size / crops.
All lens are the same (more or less) on a 1024X768 photograph, let alone smaller.
Please note that I'm writing about lens evaluation, not photographer
What is your opinion on that?

I think you are making too general a statement about "tests"

While I agree that it is virtually impossible to post photos that demonstrate absolute resolution of a lens and absolute IQ, there are a wide range of test photos that can show other aspects of lens performance that are not dependant on 100% pixle resolution, specifically but not limited to

- flair
- contrast (or lack of)
- focusing errors and flat field performance
- depth of feild and bokeh
- vignetting
- barrel and pincushion distortion
- exposure consistancy as a function of F-Stop
- chromatic aberrations and purple fringing

Additionally while not conclusive, resized photos that really "pop" right out of the camera with no PP still give an impression of image quality even though not down to the pixel level.

lets accept "test photos" for what they are. But just as an aside, I use a 22 inch monitor, in 1920 x 1200 mode. This means that at a pixlel level I can see 1/4 of my K10D image. If I view someone's image on my screen and it is sharp everywhere at this level of resolution, even though it may not be an absolute measure, it is bigger than most of us will ever print and pretty damm good!

[deejjjaaaa]

the best way if you want to prove something - upload the raw file (.pef or .dng) to some free service like rapidshare.com and post the link, unless you specifically want to show in camera .JPG... raw converter does matter, parametes used in raw converter do matter too...

[gkopeliadis]

Originally Posted by BBear

i am confused by the language used: "I think that the test shots posted here for lens evaluation are totaly useless they are 100% size / crops."
I am not sure if you are saying test shots should be posted at 100% crops or if they should be posted at full resolution (though the forum will resize it).
Can you clarify?
And maybe to help out people that are still confused about 100% crops and what not, could you post a picture in both scenarios?
Thanks!

I mean that somehow we should be able to see them (display them on our monitors) pixel to pixel as taken (through third party sites maybe?). Any resizing destroys resolution information (and other information of the lens IQ).
So I see greater or lesser photographs posted here that they say little about the lens taken.
On my 800X600 digital frame, photographs taken with my Pentax can't be said apart from ones taken by my poor olympus. On the contrary is very obvious when viewed on my computer monitor at full resolution.

[gkopeliadis]

Originally Posted by Lowell Goudge

...there are a wide range of test photos that can show other aspects of lens performance that are not dependant on 100% pixle resolution, specifically but not limited to
...
- chromatic aberrations and purple fringing

I would rule this out. PF and CA in moderate amounts is highly masked by downsizing.

Originally Posted by Lowell Goudge

... it is bigger than most of us will ever print and pretty damm good!

Hmmm! No it isn't. Modern inkjets perform miracles

[gkopeliadis]

Originally Posted by deejjjaaaa

the best way if you want to prove something - upload the raw file (.pef or .dng) to some free service like rapidshare.com and post the link, unless you specifically want to show in camera .JPG... raw converter does matter, parametes used in raw converter do matter too...

yes..yes...yes...

[Peter Zack]

I think anyone who makes the effort and takes the time to do this has provided a worthwhile service to the rest of us.

But I do agree and think if you are going to post test images you should post the original size then followed by the 100% crop. Choose the subjects with some thought to push the lens to it's limits (like flare, CA, PF etc). Make sure you use good light with proper exposures. Underexposed shots just show noise/sensor issues and are no good for evaluation.

So i'll stick my neck out. Here's some test shots I provided for someone asking about the FA50mm f2.8 macro vs FA50mm f1.4. Give me your opinion of the presentation:
50mm Macro f/2.8 vs 50mm f/1.4

[ll_coffee_lP]

Peter...your comparison in the other thread was great!

c[_]

[jsherman999]

Originally Posted by Wheatfield

Personally, I am in complete agreement, not that what I think really matters. Any thread with the subject line "Proof that the &^%$* lens doesn't suck" (or similar) is almost guaranteed to be a useless waste of bandwidth.

I disagree - I often just would like to see 'what could be done with a lens', vs.
raw pixel-level resluution numbers - those kinds og numbers are often available
on photozone and other sites anyway.

If we were to worry only about pixel-level resolution, bith the 77ltd and the
50-135 would be considered only above-average (according to photozone.)
As we've seen, they are not just above-average.

Originally Posted by Lowell Goudge

I think you are making too general a statement about "tests"

While I agree that it is virtually impossible to post photos that demonstrate absolute resolution of a lens and absolute IQ, there are a wide range of test photos that can show other aspects of lens performance that are not dependant on 100% pixle resolution, specifically but not limited to

- flair
- contrast (or lack of)
- focusing errors and flat field performance
- depth of feild and bokeh
- vignetting
- barrel and pincushion distortion
- exposure consistancy as a function of F-Stop
- chromatic aberrations and purple fringing

Additionally while not conclusive, resized photos that really "pop" right out of the camera with no PP still give an impression of image quality even though not down to the pixel level.

lets accept "test photos" for what they are. But just as an aside, I use a 22 inch monitor, in 1920 x 1200 mode. This means that at a pixlel level I can see 1/4 of my K10D image. If I view someone's image on my screen and it is sharp everywhere at this level of resolution, even though it may not be an absolute measure, it is bigger than most of us will ever print and pretty damm good!

Very well put, my sentiments exactly. I can see differences in IQ myself even in
resized images - I bought my 77, the Sigma 70, the 50-135, and the Tamron
28-75 and 70-200 based on images I saw here, at dpreview and elsewhere -
not on any resolution tests. And the 'pop' I saw in these posted images has been accurate and correct each time - when I received the lenses, my initial
impressions of the posted images have been 100% correct so far.

The 'lens doesn't suck' and club threads are invaluable, IMO.


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