50d Focus Adjustments

Post a pic and details of camera/lens settings? If the focus is out, it should show up in most pics taken at low f/numbers and at closer distances, when depth of field is most shallow, and therefore most likely to show up errors.

I would recommend that you don't use the popular focus test chart that you'll find on the web - it involves shooting a sheet of paper at very close distance at 45 degrees angle. Even if you haven't got focus problems, after trying that test you will probably believe that you have ;)
 
A suggestion to me was to shoot either 3 CF cards lined up almost perpendicular to you (along the plane of focus then), have the one on the left the width of the CF forward, and the one on the right the width of the CF backward, for short focal lengths
For long focal lengths, do the same with cereal boxes
 
coldpenguin said:
A suggestion to me was to shoot either 3 CF cards lined up almost perpendicular to you (along the plane of focus then), have the one on the left the width of the CF forward, and the one on the right the width of the CF backward, for short focal lengths
For long focal lengths, do the same with cereal boxes
Click to expand...

CF cards are too small TBH. You would need to get artificially close for a realistic test. Especially bad for wide angles. The recommended minimum distance is 50x focal length. Cereal boxes are good - three side by side. They are a sensible size, with a big flat surface and bold graphics to focus on.

Angle the two boxes either side fore and aft so that if there is a focus error, you can see what it is, but keep the centre box square on. I also prop up a ruler on one side of the middle box, with the top just behind and the bottom just in front.

Camera on tripod, everything dead square. Centre-point AF, lowest f/number, shake-free shutter speed. Set lens on infinity, then AF once to focus and shoot. Repeat three times and check. If you have a decent LCD, you can see well enough on max magnification. Zoom in on the ruler and toggle up and down it. You will see the image move in and out of sharpest focus and, obviously, the point of sharpest focus should be in line with the front of the box.

There is a short tutorial written by Chuck Westfall of Canon on this. It's similar to the above. I'll try and find a link.

Edit: here you go. Lots of good info here. If you like it from the horse's mouth, Chuck Westfall is the horse called Canon :) http://www.digitaljournalist.org/issue0812/tech-tips.html
 
If you can be bothered, shooting tethered might be useful. Then you can view the images directly on the computer monitor after each shot.

The manual can be downloaded from the Canon website as well.
 
OK here are my focus attempts (I say attempts as i am not too sure how scientfic these tests were!)

Canon 50d
Canon 70-200 F2.8 L NON IS
Canon 580 EXII

I started off with the corn flake packet and the ruler and it looked like the point of focus at 200mm f2.8 was infront of the front of the packet... See cropped image below:



The front of the box is at 24cm. This shot shows the angle of the ruler... 36cm is the back of the box and 24cm is the front to give you an idea of the angle.



I wasnt totally convinced by this testing so decided to try another method...

I got the batteries out and lined them up, 1 inch behind each other.

At 200 mm it looked fine (cropped)....



But at 73mm (was meant to be 70) things dont look very good (cropped)...



So this test contradicts the previous one where @200mm it was out. I didnt do the original test at 70mm so dont have a comparison unfortunately.

Whats peoples thoughts? Have I done the tests wrong? Is this Normal?

Cheers
Euge

P.S going to test the batteries on another lens quickly...
 
Ok here are the same tests with a 24-105 L f4 (IS off)

24mm F4 (cropped)



Thats far worse than i expected!!

This is with +20 Micro adjustments (cropped):


And finally this is 105mm (cropped and no adjustments)


I am totally lost now... either i am doing something wrong or the AF is just rubbish!

Cheers
Euge
 
eeverson said:
...I am totally lost now... either i am doing something wrong or the AF is just rubbish!

Cheers
Euge
Click to expand...

TBH bud, I'm not surprised. Follow the instructions in post #4, in accordance with the link to Chuck Westfall.

Three cereal boxes is a good target. Right size for a decent distance, flat surface with good detail, line them up side by side on the kitchen work top, three abreast :thumbs: Shoot square. Fill the frame (minimum 50x focal length distance).
 
Never ever use focus adjust - always send anything back that needs "adjustment".

Its just a band-aid masking a problem, not a fix.

SLR's and lenses are designed to be interchangeable so never work around a defect your end on principle.
 
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