Testing a new lens for quality

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Tomorrow, I'll get two new lenses - A Sigma 24-135mm f/2.8-4.5 and a
Sigma 70-300mm f/4.5-5.6 DL Super Macro. Now, I've heard several
problems with Sigma's quality control and people returning their bad
*copies*. So how do I check the lens for quality issues other than
obvious mechanical/electronic faults? Are problems with sharpness,
contrast, light fall-off etc very evident even to a beginner or should
I run some specific tests?

Thanks,

- Siddhartha
 
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In article <1109334164.767184.82350@l41g2000cwc.googlegroups.com>,
Siddhartha Jain <losttoy2000@yahoo.co.uk> writes
>Tomorrow, I'll get two new lenses - A Sigma 24-135mm f/2.8-4.5 and a
>Sigma 70-300mm f/4.5-5.6 DL Super Macro. Now, I've heard several
>problems with Sigma's quality control and people returning their bad
>*copies*. So how do I check the lens for quality issues other than
>obvious mechanical/electronic faults? Are problems with sharpness,
>contrast, light fall-off etc very evident even to a beginner or should
>I run some specific tests?
>
>Thanks,
>
>- Siddhartha
>
The most meaningful test is does it give good results in the kind of
photography you do. However, to ensure you are testing the lens, use a
tripod, otherwise you might just be testing the steadiness of your hand.
Use slide film if using a film body. Ensure you check the performance
wide open as well as at mid-apertures.

Your main problem will probably be that you do not have any reference
standard - unless you have one or more "known-good" lenses. Get a
better-equipped friend to help.

It is a little surprising to see someone buying a lens from a maker
whose quality control they have such doubts about. I guess you must have
price constraints. I have bought 3 Sigma lenses in the past and was not
over-impressed. The 14mm was just about good enough - and a fraction of
the price of the Canon offering - but does not work on my 10D. I vowed
not to buy another (though I must say the 12-24 looks a bit tempting).
--
David Littlewood
 
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"David Littlewood" <david@nospam.demon.co.uk> wrote in message
news:TP7yroD8RzHCFwZG@dlittlewood.demon.co.uk...
> In article <1109334164.767184.82350@l41g2000cwc.googlegroups.com>,
> Siddhartha Jain <losttoy2000@yahoo.co.uk> writes
>>Tomorrow, I'll get two new lenses - A Sigma 24-135mm f/2.8-4.5 and a
>>Sigma 70-300mm f/4.5-5.6 DL Super Macro. Now, I've heard several
>>problems with Sigma's quality control and people returning their bad
>>*copies*. So how do I check the lens for quality issues other than
>>obvious mechanical/electronic faults? Are problems with sharpness,
>>contrast, light fall-off etc very evident even to a beginner or should
>>I run some specific tests?
>>
>>Thanks,
>>
>>- Siddhartha
>>
> The most meaningful test is does it give good results in the kind of
> photography you do. However, to ensure you are testing the lens, use a
> tripod, otherwise you might just be testing the steadiness of your hand.
> Use slide film if using a film body. Ensure you check the performance wide
> open as well as at mid-apertures.
>
> Your main problem will probably be that you do not have any reference
> standard - unless you have one or more "known-good" lenses. Get a
> better-equipped friend to help.
>
> It is a little surprising to see someone buying a lens from a maker whose
> quality control they have such doubts about. I guess you must have price
> constraints. I have bought 3 Sigma lenses in the past and was not
> over-impressed. The 14mm was just about good enough - and a fraction of
> the price of the Canon offering - but does not work on my 10D. I vowed not
> to buy another (though I must say the 12-24 looks a bit tempting).
> --
> David Littlewood

I know where he is coming from, even "poorer" lenses have sweep spots where
there performance is good. I have a Sigma 55-200 and at mid apperture
settings at 200mm setting it is quite sharp when used reasonably close but
softens noticably on more distant objects. If you know when it performs well
then it is useable.
 
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"David Littlewood" <david@nospam.demon.co.uk> wrote in message
news:TP7yroD8RzHCFwZG@dlittlewood.demon.co.uk...
SNIP
> I vowed not to buy another (though I must say the 12-24 looks a bit
> tempting).

I've read somewhere on the internet (so it must be true ;-)) that
Canon will release a couple of new lenses coming Summer. I'd wait a
few months, and see what materializes.

Canon is not at it's strongest in the wider than 35mm range. A couple
of 24mm lenses are not bad, but e.g. Contax/Zeiss lenses (with an
adapter) kick butt (esp. in the corners and without CA). However, that
hiatus might change due to the merciless 1Ds Mark II.

Bart
 
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In article <421f8110$0$28982$e4fe514c@news.xs4all.nl>, Bart van der Wolf
<bvdwolf@no.spam> writes
>
>"David Littlewood" <david@nospam.demon.co.uk> wrote in message
>news:TP7yroD8RzHCFwZG@dlittlewood.demon.co.uk...
>SNIP
>> I vowed not to buy another (though I must say the 12-24 looks a bit
>>tempting).
>
>I've read somewhere on the internet (so it must be true ;-)) that Canon
>will release a couple of new lenses coming Summer. I'd wait a few
>months, and see what materializes.
>
>Canon is not at it's strongest in the wider than 35mm range. A couple
>of 24mm lenses are not bad, but e.g. Contax/Zeiss lenses (with an
>adapter) kick butt (esp. in the corners and without CA). However, that
>hiatus might change due to the merciless 1Ds Mark II.
>
>Bart

Interesting.

I'm quite happy with the Canon wides I have (24 TS-E, 35/1.4 and 17-35L)
- they just don't go wide enough. I'd like to think it's because they
won't produce a 12-24 until they know it's bloody good....

David
--
David Littlewood
 
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David Littlewood wrote:
> It is a little surprising to see someone buying a lens from a maker
> whose quality control they have such doubts about. I guess you must
have
> price constraints. I have bought 3 Sigma lenses in the past and was
not
> over-impressed. The 14mm was just about good enough - and a fraction
of
> the price of the Canon offering - but does not work on my 10D. I
vowed
> not to buy another (though I must say the 12-24 looks a bit
tempting).

Yep, with my limited budget I don't really have the option of going for
Canon "L" lenses. Pity Canon does not make fast zoom lenses in the
consumer non-L category.

Other than that, I checked the above lenses at a photo exhibition was
satisfied with what I handled so my main concern is QC.

As a sidenote, Sigma and Tamron are Japanese companies and all other
Japanese products I've used have very strict QC. Do Sigma and Tamron
realise that if they fix the quality issue they could be taking away
significant sales from Canon with their low-priced fast lenses?

- Siddhartha
 
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Pete D wrote:
>
> I know where he is coming from, even "poorer" lenses have sweep spots where
> there performance is good. I have a Sigma 55-200 and at mid apperture
> settings at 200mm setting it is quite sharp when used reasonably close but
> softens noticably on more distant objects. If you know when it performs well
> then it is useable.
>
>
Edmund Scientific sells a reasonably priced lens test chart based on the
Air Force standard bar chart. The poster contains complete instructions
for testing film cameras, but one has to do a little extra math, or
different procedures to get absolute values of a digicam test.

NBS (now NIST) used to sell a very good, low cost lens test set for home
testing. It is disappointing that they no longer do that. Fortunately,
when cleaning out the darkroom recently we found our old NBS test
charts. Still, we now already have the Edmund's AF chart poster taped
up on wall.
 
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