So, I decided to test my 450D and all my lenses to see (I only have 3) if I had this problem. My curiosity piqued because quite a few of the photos I took were either a bit soft, or sometimes, almost blurred. I found that my 18-55 kit lense checked out ok. The focus was dead on. But to my dismay, I found that my nifty 250 was experiencing this problem. I couldn't believe it when I did the test and saw the results. I kept repeating the test and the result was the same.
The test itself is simple. I used three AA batteries, arranged side by side, but is staggered away from me in terms of distance. So the first battery is closest to me, the second is along side the first, but about a centimeter behind the first, and the third is beside the second, but a centimeter behind the second. I set up the camera to only focus on a single point, right at the center. I then focus on the middle battery and snap a photo. If the camera were focusing properly, the center battery would appear in focus, whilst the first and third batteries would appear out of focus, as per picture 1 below.
Picture 1
Well, when testing my nifty 250, I again aimed the single focus point on the middle battery, but when I took the picture, the result was that the rear battery was in focus, the middle battery was slightly out of focus, and the first battery was out of focus. The result is shown in picture 2 below.
Picture 2
So that meant that my telephoto lens suffered from back focus. At this point, I'm not sure if it is just the lens or if it is a combination of the lens and the body. But since the kit lens works perfectly fine on the same body, I logically assume that it is just the lens, until a Canon technician tells me otherwise.
I'm quite miffed that I've got this problem. I was told that it can be fixed by recalliberating the lens or body or both. I just cannot understand how a major company like Canon, that prides itself on image quality above all other brands, can produce equipment with this kind of problem. I can understand why my friend decided to abandon Canon for Nikon. It can get very frustrating to shoot subjects for a whole day and come back for post processing and find that all your pictures are out of focus. For my friend in particular, he had this problem with 3 consecutive lens purchases, and all of them were Canon lenses.
I also found some remarks in forums that mentioned that the quality of the lens was dependent on where it was put together. The remark did not imply directly but it seemed that lenses made in Malaysia were not as well put together as the lenses that came from Japan. It just so happened that my kit lens was from Japan and my nifty 250? You guessed it. Made in Malaysia... *sigh*
The upside to this is that my problem only surfaces when I'm below 100 mm focal length. The two pictures above where from the same lens. The first picture is when the focal length is at its maximum 250 mm, whilst the second is when it is at its smallest 55 mm.
Judging from just the images above, some people might say that it is to small a problem to make a big fuss about. I thought about it for a while, thinking that I could possibly live with the lens being out of focus between 55 to 100 mm. But then I also have intentions of producing stock photos to sell, so that made this problem unacceptable as it will mean the difference between a very clear image or an out of focus one.
So I'll be sending my camera and lens for caliberating some time this week. I hope Canon can turn around the job within a day or two... *sigh*
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