[BigMackCam]

So, I got to pixel-peeping images from a few of my lenses recently, then did some tests with them wide open and stopped down to different levels. Whilst not scientifically controlled tests, I repeated them enough times that I'm happy with the consistency of the results. I came across some issues - not major, but... one lens - a zoom - showed that it is very slightly softer on the right side than the left (at the outer 10% of the image); another - also a zoom - showed that, wide open at the longer end, the slight halo around white lettering against a black background is always slightly up and to the right side of that lettering rather than a consistent "glow" all around. This is looking at 1:1, even 2:1, and even then, the issues were far from bad - but they *were* noticeable. I had to force myself to "chill out", and remind myself that the images I capture with these lenses, viewed at a typical 1:2 or less reproduction ratio, are extremely pleasing (to me, at least) - and so I decided to work on the assumption that few lenses in the consumer / hobbyist range would be absolutely perfect, and that slight imperfections really don't matter if general IQ is good. In fact, I've made a conscious decision to *not* test any more lenses as I figure I'll only get myself worked up. I'm lucky enough that I like the images from all of my favourite lenses, so... unless I notice anything untoward consistently occurring in my photos viewed at normal size and distance, I'm going to assume all is OK It got me thinking, though - do any other forum members get obsessed over this kind of thing? Am I taking the right approach, or *should* I be concerning myself with such detail? I'm sticking with my decision, but it would be interesting and entertaining to know what you think (and do)...

[TaoMaas]

I don't bother doing any formal testing on my lenses. I just make mental notes if I run into any problems because I feel they're usually situational, such as shooting wide open or at the long end of a zoom...that kind of thing.

[Steve.Ledger]

Sometimes it's best not to know things, because it's almost impossible to unknow them...

[BigMackCam]

Sometimes it's best not to know things, because it's almost impossible to unknow them...

Ain't that the truth!

[clackers]

one lens - a zoom - showed that it is very slightly softer on the right side than the left (at the outer 10% of the image);

Ooh, flip it upside down and check the resulting shot. Sounds like it's decentred.

Yeah, you have to know the report card on all your hardware, right?

[Sandy Hancock]

It depends on how you use your images. If you want to make a living from architecture, product, or astrophotography for example I imagine even slight optical problems will be important.

I don't test my lenses formally, but I'm pretty critical of my results: usually problems are of my own making, but not always

There are only three Pentax lenses I have been genuinely unhappy with:
DA15 - clearly de-centred - sent to Japan for re-alignment. Now it is perfect.
Q06 - hopeless except in the centre until stopped down to f/8. I gave it away and bought a new one, which is brilliant even wide open.
DA20-40 - very poor edges at the wide end. Returned for a refund.

[BigMackCam]

Ooh, flip it upside down and check the resulting shot. Sounds like it's decentred.

Yeah, you have to know the report card on all your hardware, right?

Ha ha Are you being serious or, as I think, pulling my leg? (I'd say taking the pi** but we're on a public forum lol)

Yeah, it probably *is* de-centered, but only when I look at it at, like, 2:1 repro... maybe a *tiny* bit at 1:1... and only tiny.... Aaaaaaargh! Now I'm thinking about it again!!!!

---------- Post added 11-20-2015 at 10:06 PM ----------

Ha ha Are you being serious or, as I think, pulling my leg? (I'd say taking the pi** but we're on a public forum lol)

Yeah, it probably *is* de-centered, but only when I look at it at, like, 2:1 repro... maybe a *tiny* bit at 1:1... and only tiny.... Aaaaaaargh! Now I'm thinking about it again!!!!

...

and then, there's my testing inaccuracies.... sigh

---------- Post added 11-20-2015 at 10:09 PM ----------

It depends on how you use your images. If you want to make a living from architecture, product, or astrophotography for example I imagine even slight optical problems will be important.

I don't test my lenses formally, but I'm pretty critical of my results: usually problems are of my own making, but not always

There are only three Pentax lenses I have been genuinely unhappy with:
DA15 - clearly de-centred - sent to Japan for re-alignment. Now it is perfect.
Q06 - hopeless except in the centre until stopped down to f/8. I gave it away and bought a new one, which is brilliant even wide open.
DA20-40 - very poor edges at the wide end. Returned for a refund.

Hey Sandy I was lucky with my DA15 - it seems very good. Same with my Q 06. The 20-40 has a reputation for so-so edges until at least f/5.6, not getting to really good until f/8... was it outside of that range?? My own 20-40 is pretty good, but not the best at edges... I normally stop down to f/5.6 minimum, and f/8 if I want frame-wide sharpness to really sing...

[luftfluss]

Like TaoMaas, I don't do anything formal. I'll go out and shoot rather indiscriminately with the lens, because I want to get a handle on how it operates and it's strengths and weaknesses - and this includes pixel-peeping. I try not to get too obsessive. As an example: I went thru 3 copies of the DA21 to get what I feel is a good one. I had to deal with exceptionally soft corners, focus issues at infinity, decentering... meh. All flaws that were obvious without pixel-peeping. Given my usage intention, I would have accepted decentering wide open if it were totally gone by f/5.6, because I seldom shoot the DA21 wide open, and on the occasions I do the subject is in the center(ish) of the frame and so decentering wouldn't be as evident. I would not accept soft corners. My 3rd (and current) DA21 is a fine copy, no decentering and corners which appear to be as sharp as it gets for that lens.

[mohb]

If you do too much testing you end up like those poor unfortunate souls who return every item at least three times and are still not 100% happy with their gear.

[BigMackCam]

... Given my usage intention, I would have accepted decentering wide open if it were totally gone by f/5.6, because I seldom shoot the DA21 wide open, and on the occasions I do the subject is in the center(ish) of the frame and so decentering wouldn't be as evident. I would not accept soft corners. My 3rd (and current) DA21 is a fine copy, no decentering and corners which appear to be as sharp as it gets for that lens.

That sounds quite reasonable. As a general rule, I don't shoot *wide* open anyway (of course, there are occasions where I do if it's absolutely necessary or DOF is a priority over outright IQ).

Glad to hear your 3rd DA21 is as it should be (my favourite lens! )...

---------- Post added 11-20-2015 at 10:17 PM ----------

If you do too much testing you end up like those poor unfortunate souls who return every item at least three times and are still not 100% happy with their gear.

Yeah, I hear about people losing their Amazon accounts for less I do return stuff - like the 16-85 I bought recently - and I've had other items that clearly were faulty that have gone back to the supplier - but I'm a pretty fussy guy, and I figure, with lenses, if the general IQ is impressive to me, it's good enough to keep...

[One3rdEV]

1) I don't test mine thoroughly, but I do pay attention while I attempt to calibrate the AF fine adjust to my camera body.

To be honest, I expect that the manufacturer has a responsibility to implement respectable quality control. That being said, I am quite appalled at the numerous reports of quality issues with camera body and lens equipment in this modern (digital) age!! My past experience with extensive camera equipment purchases were from 1984 through 1988 involving Olympus/Zuiko 35mm, Hasselblad/Zeiss MF, Sinar/Schneider/Copal LF film systems and you just didn't have any manufacturing and assembly quality problems like today. A faulty aligned lens was unheard of to me back then.

2) As much as I appreciate the likes of Adorama / B&H for their awesome customer service (e.g. faulty new equipment returns), I would highly recommend going the route mentioned by some others here and returning the faulty specimen to the original manufacture under warranty:

A) How else will they recognize and take responsibility for their poor quality performance.

B) Once corrected to proper or nominal factory specs the particular specimen will typically provide excellent performance, and likely much better than another exchanged possible fair specification sample. (This has been my personal experience.)

[geomez]

I test the IQ of my lenses. I'm a pixel peeper. I got rid of my Tamron 17-50 2.8 because it was soft and was even softer on one side than the other. I know that testing the IQ of lenses is somewhat futile considering I don't print and publish images of high contrast semi-circles and numbers. I do it because I want to know. I want to know if the softness of my images is because of me or because of my gear. I also want to know how "good" my ridiculously expensive gear is. If gear didn't cost so much, and if I didn't want to be the best photographer I can be and product the best images I can, and if I didn't spend so much time taking and processing images, I wouldn't test them. But you go to extreme measures for that which is important to you.

[BigMackCam]

1) I don't test mine thoroughly, but I do pay attention while I attempt to calibrate the AF fine adjust to my camera body...

...I would highly recommend going the route mentioned by some others here and returning the faulty specimen to the original manufacture under warranty...

...Once corrected to proper or nominal factory specs the particular specimen will typically provide excellent performance, and likely much better than another exchanged possible fair specification sample.

All good points. In fact, one lens I tested that appeared too soft wide open (and stopped down a notch) was absolutely fine once I'd spent time tuning the AF (it needed a +2 adjustment). Looking at the images from it at 1:2 reproduction, I can't see any difference whatsoever, but at 1:1 the improvement is *just* noticeable, but even then, could be down to tiny AF differences. Anyway, it's fine

Certainly, if I found I was remotely unhappy with any aspect of a lens with images at normal viewing sizes / distances (not web size, but A3 print size, viewed on screen), I would go with the route you suggest and have it calibrated. As you say, it seems all too common that factory-fresh goods do not perform to spec. I've had this with photography equipment, ham radio gear, consumer electronics / electrical goods (an example being the Kindle e-reader - I went through 3 copies before I was satisfied that there was no red/green colour blooming around the illumination area at the base of the LCD!)...

[Canada_Rockies]

I have tested my lenses informally. I know, for example, that my M 400/5.6 has ridiculous amounts of CA and PF at apertures wider than f/11. One good thing my new to me K3 will do is allow me to get the shutter speeds up by increasing the ISO way beyond ones that were available on my K10D and they will be quite usable.

My current testing series (chasing little birds by the feeders) is using the AFA 1.7x on the back of the DA 55-300 giving me 510 mm on the math. The combo might allow me to use it instead of the M 400. You can find a first few on my Flickr site if you like to pixel peep. Have fun.

[dadipentak]

I test pretty informally. Issues have to be pretty pronounced for me to notice--but it has happened.