which is the canon lens with the worst quality control ? your opinion

Hi
i like to use the 17-40 F4L with my 5d or 5d mark2

but to get a good copy , i had to replace twice

the first and the second were soft ,the center of the lens and mostly in the middle and in the corners
never understood if a good/bad copy is due to a not perfect focus ,because the glass is glass

i mean that maybe a good copy connected to a working AF (calibrated)


well i did not send the first and the second lens to canon , i went to the store and asked a replace

the third lens is perfect , sharp in the center and in the middle

could you share your experience with me ?
based to your experience , which is the worst lens talking about quality control ?
is matter of af ? because in short glass is glass , can't figure in line production (almost made by machine ),what could make a lens a Bad copy


i remember once i read a long article ,but now i can't find it

thanks
cheers

Probably the old 18-55 non-IS kit lens or the Nifty Fifty.

? 1200mm.
As not many people own it

The nifty fifty and 50L maybe.

LowriderS10 wrote in post #11852804
Probably the old 18-55 non-IS kit lens or the Nifty Fifty.

KY707 wrote in post #11852824
The nifty fifty and 50L maybe.

never had a issue with the 17-40L with a full frame ?

but what makes a lens a bad copy ,outside the autofocus system

Nifty fifty and 50L. Not Canon's best focal length.

50L

mantra wrote in post #11852791
Hi
i like to use the 17-40 F4L with my 5d or 5d mark2
but to get a good copy , i had to replace twice
the first and the second were soft ,the center of the lens and mostly in the middle and in the corners
never understood if a good/bad copy is due to a not perfect focus ,because the glass is glass
i mean that maybe a good copy connected to a working AF (calibrated)
well i did not send the first and the second lens to canon , i went to the store and asked a replace
the third lens is perfect , sharp in the center and in the middle
could you share your experience with me ?
based to your experience , which is the worst lens talking about quality control ?
is matter of af ? because in short glass is glass , can't figure in line production (almost made by machine ),what could make a lens a Bad copy
i remember once i read a long article ,but now i can't find it
thanks
cheers

Going through the number of lenses, (not buying and returning ) I have a very strong opinion that it is very very rare to receive a 'bad' copy. It actually means that the lens is defective.
A case of a bad copy of the photographer, who just becomes a trouble maker is much more common.

I feel extremely lucky with my 50L :P

mantra wrote in post #11853615
never had a issue with the 17-40L with a full frame ?

but what makes a lens a bad copy ,outside the autofocus system

I don't own a FF and my 17-40L was a wonderful and reliable piece of glass that provided top-notch results.

I was initially going to say 50 1.4, however I think that is a poorly DESIGNED lens...things went wrong well before QC on that one lol

All of the 50s really...luckily my 50L is awesome!

helloagain36 wrote in post #11854446
All of the 50s really...luckily my 50L is awesome!

The 50mm compact macro is very good. Slow, but good.

24-70L....

TooManyShots wrote in post #11854517
24-70L....

sad
is one of the more used lens

Refresh Image wrote in post #11854355
Going through the number of lenses, (not buying and returning ) I have a very strong opinion that it is very very rare to receive a 'bad' copy. It actually means that the lens is defective.
.

did not got the meaning the number of lenses...

by the way , the first copy and the second were so soft in the center and more more soft in the middle

the third copy(lens) amazing sharp on the center and sharp on the middle

really can't understand what made the 2 lens so soft
AF ? again glass is glass , really can't understand what could cause a soft lens

I suspect some of the posted answers are not based on quality control, but by the typical level of performance of the named lenses.

Indications of poor quality control would most likely show up as deviations from the intended performance of the lens. So, the fact that all copies of a particular lens perform "poorly" doesn't necessarily indicate poor quality control. It could mean that the design is defective or that the design delivers exactly the level of performance that the manufacturer intended, but that level of performance is not satisfactory to the user.