Old Timer Loc: Greenfield, In.

As most of you know I have trashed the Tamaron 18-270 mm that I recently bought and was not satisfied with it. Now the question is, I have two Canon xsi as for being set up they are the same I think. Now the problem I get better pictures with one of them than the other. They are sharper the colors are even more vivid.
Would the difference be in the auto focus? Or would it be in the sensors and with in tolerance and would match up to one better than the other. My other lens does not seem to make any difference, but they are Canon lens.

dasloaf

Someone once gave me a lens to use that their camera couldn't get a picture worth a dam with it. Mine loved the lens and took awesome pics with it. Same camera, same settings, same lens but with different results. We figured different people assembled them with different tolerances and results!

MT Shooter Loc: Montana

Quality control.
Or lack thereof.

birdpix Loc: South East Pennsylvania

Check that camera and lens combination for front or back focusing. Make sure your settings are identical. Different modes, like landscape, portrait etc have different parameters set for things like saturation, vibrancy, sharpening etc.

haroldross Loc: Walthill, Nebraska

I would go into the menu settings and return all the custom settings to their default. Sometimes I change one of the settings in the menu without realizing it. Just recently I was having problems with flash picures only to realize one of the flash settings was changed to 'second curtain'.

jerryc41 Loc: Catskill Mts of NY

A big difference between the top companies and the others is quality control. Nothing is perfect, but how large an error will a company allow in its products? Each item that is rejected and sent back costs them money. Letting more items through keeps the costs down. Where do they draw the line?

Many people here have said that they bought a Canon/Nikon lens, weren't satisfied, and sent it back for another. The second one worked fine. So, was it user error or a less-than-perfect lens?

saichiez Loc: Beautiful Central Oregon

Tolerance Issues.... relatively normal. Could be called Quality Control, but could be normal within a companies Tolerance Specifications.

Take a lens. That lens is designed with a certain set of tolerances symbolized by a plus or minus range for "being within specification".

Now, take a camera (same company). That camera's lens mount had a "final specification" with it's own plus or minus tolerance range.

Now, add that the tolerance range is never announced for each item. The item simply has to be within the plus or minus tolerance.

You could have a lens within specification, BUT at one end of the tolerance range. Your camera could have a mount within specification BUT at the other end of the tolerance range. Now realize that when you buy these items, you cannot specify at which point in the tolerance range your particular item falls.

So, the manufacturers offer a service whereby if you have a lens that is "front focusing" or "back focusing", you can send it in and they will check and adjust where your tolerances fall. This is more common than most people might imagine.

Now you raise an unusual scenario... Using one camera with two of the same lenses. One lens may be at one end of the tolerance scale, and the second lens at the other. It's not Canons fault, if the lenses are within the tolerance range of the stated specification.

Add in third party lenses, however, and you may not get help from the camera manufacturer to adjust the tolerances for the third party lens to your camera tolerances. It's just a way of doing business, and Canon is not responsible for your choice of a lesser priced lens.

Now, how do people sell lenses for less than Canon makes and sells them for.... Quality Control. The lesser priced lenses from other manufacturers don't have the quality built in. Guess what? Tolerances are a big part of "Quality Control".

That's why when you read the reviews on third party lenses, you may see some good reviews, while you may also see more that say, "I bought one of those and it was a POS!!!!"

It's not so much that peoples opinions are all over the place. The equipment is actually suffering from a wider range of QC or tolerances.

For instance, it's not uncommon for professionals and very particular advanced hobbyists to send camera and lens combinations that seem not to be performing well together, in to the MFR for pairing and adjustment. The next new lens of a different focal length may, or may not, exhibit problems. If it does, then the body and lens go in for check and adjust. However, if one gets into this very much, one must be sure to tell the MFR that the camera is already adjusted to another lens.

Now, in the workaday world, QC from a good manufacturer and tight tolerance ranges create good workable modular systems, ie. camera bodies and lens. However, if you are too cheap to buy a 400m lens, then you may buy a 2X convertor.

Guess, what... you are stacking tolerances. It's less likely that a 2X converter on a 200mm lens will ever give perfect results. Consider three components now, all at various ends of the tolerance range. No Go!

So, not to belabor this, one might ask, "Why don't the manufacturers tighten up their tolerances and deliver a better product?"

Certainly they could do that... The result would be reflected in the higher prices needed for better machining and assembly....

Hence Canon builds "Kit" lenses vs. Canon's "L" series lenses.

Kit lenses are made on an assembly line, put together from parts that were machined at a different set of standards, and checked out by "older employees with shaky hands"

L lenses are made on an assembly line with more precisely machined parts and checked out by "fit young employees with good eyes".

Then, as in the car manufacturing business, you have Friday lenses where people are excited to get off early and start partying for the weekend, and Monday lenses/cameras, where people are working off a hangover, on your new stuff!!!

Disclosure. I used Canon in this piece simply to maintain a consistent MFR as example. This article has no bearing on feelings about the quality of Canon in my opinion.

jerryc41 Loc: Catskill Mts of NY

Which is why racing engines are "blueprinted," set up to the best specs possible, as specified by the manufacturer.

Wabbit Loc: Arizona Desert

Hey Doc ..... I'd look closely at the settings. If they're the same I'd contact Canon. There may be something that they could do for you.

coco1964 Loc: Winsted Mn

With the great reviews that the Tamron 18-270 have gotten and my own personal use of the lens I'd say you have some problems with camera/lens tolerance. That lens will take tack sharp photos and if you don't believe me I can give you examples. With one of your Canon lens doing the same thing it would justify the conclusion given by saichiez that it is your lens/camera combo that's the problem. Get it checked out before you start discarding lens........

deanc2006 Loc: lancaster ohio

some cameras have micro adjust that you can set my 7d for example.

Merlin1300 Loc: New England, But Now & Forever SoTX

Many are quite happy with the Tammy 18-270 as a value lens. Mind you - it is a jack of all trades, master of none - so if you're expecting it to be as sharp at 270 as the Canon 300mm "L" prime, you're gonna be disappointed. IF all your other lenses work well on your XSi - I suspect you may have gotten a bad copy of the 18-270. I have no compunction against sending a questionable lens back to the vendor and requesting replacement. If you indicate that the lens you received was 'defective', some vendors will even provide return shipping!
After doing my homework - I selected the Canon 18-200 as my primary walk-around - and have been quite happy with that. I recently received a Canon 15-85 that had a small dust speck on one if the internal lens surfaces - - sent it back, and the replacement was perfect.
Follows is my favorite comparison of walk-around lenses for the Canon
http://www.juzaphoto.com/article.php?l=en&article=35

coco1964 Loc: Winsted Mn

And you'll pay about triple for the 300L prime---it should be clearer..................

DougW Loc: SoCal

Try both cameras with both lenses on manual focus. If sharp I would say there is an auto focus problem. That dang German Otto causes a lot of problems.

Merlin1300 Loc: New England, But Now & Forever SoTX

And it IS !! Check out SwampGator's shots (he uses it with a 1.4 TC). My next lens will be the 70-300L - - which is almost as good as the 300L prime, but the Zoom capability is more important for me. I'll have to save for a couple of years to get it though :(
My main point - however - was - - you can never get it ALL in one lens. Price, Speed, Range, Size, IS {VR, OC, Whatever}, CR, Bokeh, etc etc, are all factors one must consider when buying a lens.
In addition - - there is certainly variability from one lens to the next - so - - if a lens does NOT seem to live up to it's reputation - - it may be worth exchanging it for another copy.