When Canon 300D and, later on, Canon 350D appeared on the market, digital reflex cameras stopped being a luxury and became very affordable. Consumers were eagerly switching from regular digital cameras to the reflex ones hoping for a miracle. The problem was that this "miracle" was selective and not everyone was able to create it. There arised issues of changing optics and autofocus; some got to question why they would trade their always-so-sharp-picture for a blurry image and so on and so forth. This article will discuss ways to adjust the autofocus of this particular camera which is, from my point of view, the key problem of Canon 350D. The rest depends on you and your skills in mastering a reflex camera.
   So, finally you have become a proud owner of a reflex and, after a wek or so of using it, you notice that the focus on your images drifts either backwards (creating a so called "back focus") or frontwards ("front focus"). My recommendation is simple: find out the address of the nearest service center and submit your camera for an adjustment (it is usually part of your warranty).

   Then, whilel your camera is being serviced, you can read my methods and observations on tuning of the autofocus.
 
Preparation.

   The process of tuning is mainly about adjusting a screw located in a shaft under the mirror.

               fig. 1

   How to find it:

1. Clean the area where you will work from dust.
2. Сharge the battery (always keep it chrged). When you are cleaning a sensor and the battery suddenly gets discharged, the camera should give a sound signal (the paperwork does not mention it, by the way. However, NEVER CHECK THIS MODE.
3. Remove the lense.
4. Lift the mirror with using a "cleaning of sensor" command in the main menu of the camera. Warning: before lowering of mirror make sure there are no objects on its way as any object can cause a breakdown of the shutters and the mirror itself. Some people ignore the "clean the sensor" function and use their finger (the camera is turned off) lifting the mirror. Then they turn the screw - it might feel uncomfprtabel at first but it is safe as the mirror won't go down in case of an accumulator failure. Besides, the sensor will get less dust.
   After all these manipulations, on the side, closer to the sensor (see fig. 1) you will see an adjustment screw. It is quite hard to get to and to be able to turn it, you might have to bend the hex-key (fig. 2, 3).

                                   
                                                               Fig. 2                                                                                 Fig. 3

   Now you can lower the mirror (see the camera manual and precautions) and turn off the camera.


  What is needed for the adjustment :

1. Patience and accuracy;

2. Hex-key (see figure 2 and 3). The diameter of key should be 1,3 mm (figure 4)  or to 1/16-inch key from CRAFTSMAN (that's the one I was using) if you are in a country  with a different measurement system; 3.A ruler or a measuring tape (a strip of insulating tape or a nail enamel (burgundy or any dark color) in order to make a strip;

рис. 4

4. A tripod;

5.  A lense, preferably with a diaphragm  2,8; 2,0; 1,8; 1,4 , etc. We will use a completely open diaphragm;

6. A protractor for a precise measurement of the angle between the camera and the ruler;

7. Well - illuminated place so that the camera could focus easier.

  Now you know, where the adjustment screw is and have everything to use it..

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
!!! WARNING!!! :
1. Any interference in the construction of your camera can entail its breakdown and terminate your warranty from the manufacturer.
2. Read the article till the end before acting.
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

   Let us move on to a standard method of the autofocus adjustment in cameras CANON EOS (this method is often discussed on different forums).

Example.

  Let us take a look at the option , where we use a ruler and a strip of insulating tape as a marker:

а)Place a ruler onto a horizontal surface and mark it as shown in figure 5.
б) Put the camera on a tripod at the angle of 45 degrees to the ruler with the marker and at a distance of ~25-35 sm
в) For a perfect result you can use "preliminary lift of mirror" mode and to take a shot in an automatic mode.


            Fig. 5

   Take 3 consecutive shots focusing as shown in Fig. 5, with a diaphragm open to the maximum, each photograph re-focusing on the marker. Trace the results on the monitor. They must be identical. Now you will be able to determine whether you have a backfocus- (Fig. 6), front focus (Fig. 7) or if everything is ok (Fig. 8).

                            
                                          fig. 6                                                                    fig. 7                                                                 fig. 8
  A small inaccuracy of +/- 2-4мм is considered to be normal. (I cannot determine your criteria for autofocus, but I can say, based on own experience, that you will always have time to damage your autofocus so DO NOT HURRY with THE ADJUSTMENT of your camera and MAKE MORE ATTEMPTS PHOTOGRAPHING THE MARKER). And remember: having decided to turn the adjustment screw, you WILL NEVER BE ABLE TO ACCURATELY RETURN IT to THE INITIAL POSITION. So tere is a choice to make.

  Now let us move on right to the turning of the adjustment screw. To do this you need to accurately remove the camera from the tripod without changing its position, and then as it was spoken above:
- verify charging,
- remove the lense,
- raise themirror,
- carefully insert the hex-key into the opening,
After that slightly turn the key (with a slight effort so be careful not to damage the sensor or other parts located in the shaft).Remember what side you began to turn the key because you might have to do another turn or two either side. Pull out the key from the opening and the shaft after turning, lower the mirror as it says so in the manual. Now take a test photograph or a couple of them from the tripod checking the results on the monitor of your computer. Has the focus been changed? If so, you need to determine if you need to keep turning the key or not; if the focus shifted to the other side, you need to repeat all the operations but turning the key in reverse.
      Now it seems to you that the focus is where it should be.If I may just suggest doing a simple test here: take a match, put it horizontally at a distance of 2 sm from the camera (focal length of ~50 мм) and try to put the central point of the focus not its head (Fig. 9).

        fig. 9
If everything is right, when the focus grabbes the top of the match your camera will make a sond signal; of the lense is drifting side to side unable to focus, it means that you have turned the key too far.

The way things were with my camera:
I did what I described above myself. It seemed quite simple but risky as there was no who could tell me if he had done it or not, if he it was successful and if it all was worth the effort. I was surprised at how easily I got results from the adjustment with the ruler (it tool me some 25 minutes to adjust my autofocus). While doing it I would take shots of an objext located in front of the camera to control the accuracy. I have been using Canon REBEL XT for a year now since this operation and I am satisfied - everything is in focus!

This was achieved by combining several methods of adjustment:
1. a ruler place at an angle of 45 degrees
2.an objext placed in front of the camera:
a) an object located 40 sm away (for example, a ruffled lid 1-1,5 sm diameter as it will allow you to spot the back focus)

b)1 meter away

3.horizontally placed match (match is needed only to control the vertical focus: for instance, if you try to focus on the tip of one's nose, a camera might focus on the upper lip instead)

4.lighting should be good everywhere which is a must for all modes.

Conclusion:
I managed to adjust the autofocus properly. Perhaps, I just got lucky and turned the key in the right direction?.. However, I don't want any more experiments (the picture displayed here was taken the evry next day after adjusting AF and cropping).

Advice:
Do not use any of these methods of you have an opportunity to have your reflex camera serviced. It is very unlikely that you will do better than that - you can easily make it worse. Besides, there is a lense factor - it should be correct.

The disadvantages of self-adjustment :
- dust and hex-key can damage camera, during the operation.
- constantly make sure that the battery is charged.
- other points of self-focusing begin to blur substantially.
- adjusting screw is a point of no return.

Advantages:
+ you do not entrust your treasure with someone else or you are far away from a service center.
+ saving the money (however, this thriftiness might cost you a new camera))
+ doing this procedure once enable you to repeat it as needed

     Author Borisov Dmitry
References to the articles, placed on this site, reprinting and publication are allowed only with the agreement of the owner of the site. .
© 2006 all rights to this material are protected by legislation.