International Photographers Association of Los Angeles 洛杉磯國際攝影家協會

I carefully tested XSI with 3 lenses. The test results are very surprising.

Test Method:

靶子：在一页杂志的中心位置画了一条横线（如下图）。
相机：XSI加在三角架上，使镜头距离靶心4尺，切入角约45度。固定。
镜头：分别用了三个镜头，以AF方式拍摄。
拍摄：用快门线，每个镜头在确定对准靶心后拍摄。每次拍摄后逐渐改变F-Stop。每次启动快门之前手动破坏掉聚焦。
评估：测量实际聚焦中心距离靶心的距离。

结果如下，请器材专家发言。
对于Canon产品，我认为这不正常。网上有很多人提出Xsi有focus 不准的问题。不知道我所发现的是不是普遍问题。有没有其他人做过类似测试或有兴趣比较？

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学习中

Looks like it's time to upgrade the camera body.

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Live life by design, not by default.

The 3 charts have totally different characteristics.

The first one with the 50/1.4 lens, with gradual increase of F stop number, the focus shifts in a linear fashion. It means, with this lense, I should try to set aperture to 3-4.5. It is bad for the money I spent for a F1.4 lens.

The second one, lens 18-55mm, has front focusing problem.

The third lens, the 55-250mm, is right on. If one tests the camera with this lens, the result will be perfect.

Since I have little knowledge about lens and camera mechanics, I cannot say if this is a camera issue or lens issue. However, I know with the 55-250mm lens, the camera can focus. The same camera with the 18-55mm, the focusing can be consistently off. With the 50/1.4, it is more complicated.

Before chatting with Canon techs, I would like to know from fellow photographers how bad the charts look. If anyone have tested his/her machine or is willing to run a test, I'd love to know the results. If is very good to know how our machine performs after all.

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学习中

Very intriguing findings!

I have never found the need to do this kind of test because my 20D, 5D, and 6 lenses provide good results most of the time.

Greg, it is time to take your camera and lenses to service center for calibration. (I have never been there yet)

I agree with Fengyu. I used to use both Canon and Nikon. Now I am only using Nikon. But in the past I have used Canon 20D, 30D, 40D etc with various Canon lenses and have not noticed the issues you're encountering. Canon XTI and XSI bodies are more like consumer grade cameras. If you do a search online you will see similar complaints from other XSI users regarding inconsistent focusing with different lenses.

For more serious photography, perhaps a Canon 40D, 50D or even 5D will give you better results and more satisfying photographic experience. However, if you don't have too much invested in Canon gear, you can always try switching to Nikon D90, D300 etc.

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Live life by design, not by default.

You two are right. From quite some time I have been wondering if my camera AF is really soft. Now that is confirmed. It varies. From reading the many posts online, I know that having this fixed is not simple at all. It is time to save up.
I will be out in New York next week, so I will not turn the whole bag to Canon at this time. Instead I will learn to use it wisely. I will try to figure out the ways to compensate each lens. In the worst, when use low DOF, I will have to take multiple shots each time and then cherry pick.

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学习中