Canon 5D strong back focus with EF 28/1.8

[antanas26]

<p>Hi all,<br>

Canon 50D focuses fine with 50/1.8II and 28/1.8. Canon 5D focuses fine with 50/1.8II but NOT 28/1.8.</p>

<p>Regarding 5D with 28/1.8, I "felt" there was something wrong before but only now tested more thoroughly. When shooting text at an angle, AF does not not look too terrible (all DOF is behind the target but the target is still more or less acceptable). But when shooting at longer distances, back focus is very noticeable. For instance, aiming 3 meters ahead, maximum sharpness is more like at 3.50 m. While aiming at 4 meters, it's perhaps 5 or 6 meters. I can however get consistent accurate focus when overriding AF by turning a focus ring a tad. All testing was done at max aperture.</p>

<p>You would tell me -- AF microadjustment. But sadly, 5D does not have this feature. And sending to the manufacturer/dealer is not an option.</p>

<p>My question would be, is there anything I can do myself to fix it, or will I have to "get used to it"? Thanks.</p>

[PuppyDigs]

<p>Sadly--short of buying a camera with MA--you're stuck if you're unwilling to return the lens or have it calibrated by Canon. This summer I bought the EF 28 2.8 IS USM to use as a "normal" lens on my Rebel SL1 and it front focused terribly. I could MA it perfectly on my 6D but the SL1 lacks the MA feature so back it went. I bought the 24 2.8 IS USM and it was spot on without MA so it all worked out.</p>

[antanas26]

<p>Thanks for your response. But still it is puzzling to me. Is really the lens itself that is to blame? Because the same lens works perfectly on another camera. Perhaps the camera is not calibrated to perform equally well with different lenses? It looks to me that if a lens is faulty, it would perform badly on all camera bodies (given that the bodies are all okay).</p>

<p>Please share your thoughts about this dilemma. I just read one Nikon topic discussing whether AF accuracy problems are caused by camera or lens, and there was no straight answer...</p>

<p>PS. Camera no longer has any warranty and lens was bought like half a year ago from Hong Kong (from ebay) so obviously does not have local warranty. Shipping it back to where it came from does not sound very appealing...</p>

[Marcus Ian]

<p>It's commonly caused by both. The bottom line is that often manufacturing tolerances allow for discrepancies to 'add up', though equally as often they cancel each other out, or are near zero. If the equipment is well used, or has been whacked one to many times (and what lens/camera hasn't?), problems can certainly arise.</p>

<p>With fast primes (and their shallow DOF WO), this problem is severely compounded.</p>

<p>Personally what I would choose to do would be to send the lens and 5D off to Canon (though I'd send your other fast primes too) to have them all adjusted to work together perfectly. You will need to pay for this service, but it won't be a ridiculous cost, and will likely be well worth it. Once they return, you can do MFA on your 50D, and everything should work fine with everything.</p>

<p>You certainly CAN do it yourself, but without an optical bench, you'd be shooting in the dark at a mouse in the forest, not impossible to hit, but you'll need hella good luck!</p>

[antanas26]

<p>Thanks for your explanation. I would be eager to take a chance adjusting it myself. But all I can find on the internet are instructions how to do microadjustment in camera. Can you give an idea how I can calibrate the 28/1.8 and 5D?</p>