Newbie Question: Good/Bad copies of lenses

DavidC1980

DavidC1980

Messages
246
Name
David
Edit My Images
No
Hi,

I read lots of threads and reviews about certain lenses where people make comments about having had good copies and bad copies of a lens. What I want to know is, when you got a new lens and realised that it's a bad copy, have you got it exchanged FOC under warranty?

The comments from people who have said that they have had 2 bad copies of a certain lens made me wonder whether that meant they'd exchanged a couple until they got a good one, or did they just sell the original and take a chance with another.

It's a newbie quesiton, but one that's been bugging me.

Thanks,

DC
 
I don't know if its good copy/bad copy but its possible that you can get a lens that doesn't perform at its best with a particular camera yet will be ok on another. It's all down to manufacturing tolerances. A lens at one end of its factory tolerance and a camera at one end of its factory tolerance may just not gel together. Doesn't mean that there is anything wrong with either.

I had a Canon 500mm f4 that front focused by about an inch and a half on my 1D MkIIN. Doesn't sound much but wide open with such a shallow depth of field it was an issue. I changed it for another copy that was spot on. With the introduction of MA on some camera bodies it means that slight variation in tolerances can be tuned out usually. I'm sure that every so often a lens comes along that is a Friday 5 o'clock job though.
 
I would also bring into the equation the fact that sometimes it's the user not the lens, especially when they say they have tried 2 or 3
 
Gremlin said:
I would also bring into the equation the fact that sometimes it's the user not the lens, especially when they say they have tried 2 or 3
Click to expand...

That's a good point. If you say that a lens isn't performing as it should on a body then you have to be methodical about how you come to those conclusions. Just taking a few shots handheld and saying these aren't sharp doesn't prove anything as there are too many variables.

I remember the first time I used my 500. I thought I was going to get great shots of everything I pointed it at. Silly boy that I was. I didn't have a clue how to use a big lens properly. Have got a bit better now though.
 
Yep know that feeling well when I got the sigma 150/500 and had heard there were some bad copies, I had a few problems with using and thought the worst, the a friend borrowed when we were out and got some amazing pictures, since then and with practice I have realised it was me not the the lens :thumbs:
 
I've got a Sigma 150-500 OS and it's a fantastic lens and has got me some super photos on my 5D3. When I bought a 70D a couple of weeks ago it was misfocussing a bit. I altered it by just a couple of points with the MFA on the 70D and it's spot on.

Mainly the problems occur with bodies that don't have MFA built into them. I had a 550D that I started off with and every lens apart from 1 was spot on. I had to send a Sigma 18-125 back as I couldn't get a well focussed shot but when I got the replacement it was fine. In 3 years I've had about half a dozen bodies and well over a dozen lenses (sold some off to get others) and only 4 of them (50 f1.8 on a 5D2, 18-125 on 550D, 100 L macro on a 7D and now 150-500 on the 70D) have needed any MFA.

I'm sure there are some lenses that have had problems with the manufacturing and have been classed as 'bad copies' but in general most can be corrected with MFA on the bodies that have it.
 
Last edited:
Gaz J said:
I don't know if its good copy/bad copy but its possible that you can get a lens that doesn't perform at its best with a particular camera yet will be ok on another. It's all down to manufacturing tolerances. A lens at one end of its factory tolerance and a camera at one end of its factory tolerance may just not gel together. Doesn't mean that there is anything wrong with either.
Click to expand...

This.

Al the lens (from according tamron) are built to a generic spec within tolerances much like car engines which means that two engines or lenses out of the same factory on the same day can perform differently.

My 17-50mm 2.8 Tamron was front focussing slightly so I sent it to Tamron and they fixed the issue.

When I asked about it they basically said the above and also mentioned that they had 10 Canon 7D bodies ( i beleive he said 7D) sent to them and 8 out of the 10 needed different adjustments to attain the same results.

How 100% that is i'm not sure but that is what Tamron have told me when I have sent lenses off to them with my 60D's to be paired up.
 
Plenty of bad lenses around if you look for them.

There are 3 main reasons:

1) the lenses (the elements) are made deformed. It is less likely / or less severe these days with automated process, but you would commonly see air bubbles, rough edges and all sorts from glass back a couple decades ago

2) Assembly process issues (quick and dirty job), cheap and soft plastics used for lens assembly and so. This is very common these days. They try to make too many too quick.
This will appear as soft focus, one side softer and so on. There are some forgiving cases when it is enough to microadjust, but frequently there is more behind it. Like some very soft sides that are bad no matter what (most people accept it as normal when it should be returns)

3) accidental damage. It doesn't have to break and shatter, in fact could be no marks at all (i.e. dropped a whole bag from high up, or a delivery parcel {NEW lens}). You could only guess what happened, but some things may be off.

All in all you can get junk if you are unlucky and I had seen examples including 135mm L, and many more from both Canon and Sigma.
 
Great stuff. It's been the comments on the Sigma 150-500 that prompted me to ask the question. That and how I found my 70-200 seemed to be missing focus at Silverstone last weekend.

I'll have to set some time aside to find the correct MFA settings with my lenses. I think the only space large enough to do the 70-200 + extender is my office at work :S I may get some funny looks doing that.
 
Canon recommend 50 times focal length for calibration. I do mine at 25 times and then check them at longer distances with some random shots.
 
The talk has been about autofocussing, but lens examples have other variations that can be well out of line - lateral chromatic aberrations for example.
 
As i buy all my gear on line i tend to send it back if im not happy with it.
I would never buy a lens with the intention of doing this, but feel safe with companies like Amazon that make it painless.
In fact at this time last year i had two poor copies of the 17-55 f/2.8 sitting here at work. Both were de centred to a certain extent, and having owned this lens before i knew this was not the norm.
 
You must log in or register to reply here.
Back
Top