How to test a lens copy in a shop?

[wibbly]

I've read that even L lenses vary somewhat copy-to-copy. Is the only way to ensure a good copy to buy from somewhere with a very good returns policy and history, or is there a way to 'test in the shop'? For example, I could check the smoothness of operation (mechanical) but how would I ever detect optical problems other than cafefully taking some samples and then looking them 1:1 on a monitor?

If I can't, I might as well buy on-line

W

[samdring]

Testing in the shop is good but really only for 'gross error check' in my opinion.

The couple of lenses I have been less than happy with were due to sharpness and even then only by forum members stating their comparison experience. (Lens A [which I bought] is sharper than Lens B [which I already had] and it wasn't!)

I have just re-read that paragraph and even I struggle to understand myself :cry:

[wibbly]

Anyone ever got an L lens so bad it was worse than a non-L?

W

[daveh]

Anyone ever got an L lens so bad it was worse than a non-L?


There are lots of opportunities for apples and oranges problems with such a wide-open question. For example many non-L primes will outperform L zooms. Some Ls will only slightly outperform their non-L counterpart but give you an extra f-stop or so.

"L-ness" covers a lot of ground.

[wibbly]

Sorry I should have been clearer. More a questin of if the L quality actually varies quite a lot copy to copy, or if the differences tend to be subtle. A question of Canon'd QC really.

J

[DeeplyDigital]

I can only talk for the Ls that I have bought, one of them used and
about 10 years old.

Never had a problem with an L-lens yet (but then again I only have
a few) and would at this stage trust them without trying.

Yesterday I tried a second-hand 24mm f1,4 on my 20D.
I tested it on bricks etc. just outside the shop, the
camera salesman close up etc, at different settings.

Then I went home and looked at my RAW files.
Sharp, nice bokeh - delicious.

J.
-
had to edit this as I had forgotten your original question when I started to think (drool) about that little lens...

[robertwgross]

Testing in the shop is good but really only for 'gross error check' in my opinion.


Haven't we got a better term for that?

---Bob Gross---

[Jesper]

Testing in the shop is good but really only for 'gross error check' in my opinion.

The couple of lenses I have been less than happy with were due to sharpness and even then only by forum members stating their comparison experience. (Lens A [which I bought] is sharper than Lens B [which I already had] and it wasn't!)

I have just re-read that paragraph and even I struggle to understand myself :cry:

Hmmm..... I think you should watch out that you don't let other people make you crazy with all kinds of things they say in Internet forums.

If someone says "lens A is sharper than lens B", or even if five people say it (maybe they're just repeating what they've read before?), would you allow that to make you feel bad about your new lens, which seemed to work great before you read it? And how did you do your tests, did you really put the camera on a tripod and did you take all the appropriate measures to do a good comparison test?

Stop "measurebating" and start taking photos..... :roll:

I'm sure 99,9% of the L lenses that are sold are good, and if there really is a problem, go back and exchange it. No need for paranoia and elaborate lens testing in the shop before you buy something.

(You could bring a laptop, camera and tripod and try out your copy in the shop if they let you, but I bet the people in the shop are going to look strange at you when you are setting your stuff up....... :roll: )

[BearSummer]

Testing in the shop is good but really only for 'gross error check' in my opinion.


Haven't we got a better term for that?

---Bob Gross---

Well I guess we could call it "Doing a Robert", "Bobing the lens" or "Having a quick Bob".

What do you think?

Best regards

BearSummer

[robertwgross]

For the Brits: ... and Bob's your uncle.

---Bob Gross---

[ScottE]

Anyone ever got an L lens so bad it was worse than a non-L?

W

I have a 17-40/4 L that is not quite as sharp as my 28-135 IS on the 28 to 40 mm part of its range. It is sharper at the shorter end of its range.

On the other hand, I am lucky to have a very sharp 28-135.

[ron chappel]

Yep,testing for obvious major flaws is the only easy thing to do in the shop.
Maybe a shop will let you compare several of the same model .I've heard that many shops regularly do this for pro's because of the money they spend there.However to spot the *tiny* expected differences you'll have to:
a)Use a good tripod !
b)forcing the flash to work is a good idea in a dim shop.Flashes fire at 1/500th upwards so are good for artificially freezing any movement
c)take several pics,refocusing each time!AF is pretty acurate but can give slightly off results if the wrong edge of the focus point catches something it shouldn't.
This is really very easy to do.Just methodically fire off several shots,zoom in to maximum in playback and choose the sharpest.
d) Which brings me neatly to the last thing.
Yes -if you get good steady shots you can easily compare lenses by looking at the results on the camera screen :) .You don't need a computer.Just zoom in and scroll back and forth to find any difference :)
-note - you should arrange shots so that competing examples are side by side in the camera
-also,if you want to test corner sharpness it's just as easy (make sure you really have focused on a corner object though! Too many people forget to do that so they are really comparing out of focus corners to one another :roll: )

[ScottE]

Before I started shooting digital a shop let me evaluate a used lens by bringing in my camera and tripod. I bought a roll of film and tooks some shots in the store at close distances and outside the door of the store at the brickwork and signs on the buildings across and down the street. The shop then ran the film through their developing machine and I examined it on their light table with a loupe.

Now I would take the same shots with my digital camera and review them at 100% magnification on a computer. I would also take the same shots with one of my good lenses for comparative purposes.

This is an advantage of doing much of your business at a local shop where they get to know you and will go out of their way to give good service.

Scott