Inconsistent focusing with new Canon 50mm and 85mm F1.8 lenses. A distressing problem

[250Gimp]

Just so you know...you have to use mirror lock up along with thte timer or remote shutter release to prevent mirror slap. This is in the Custom Function menu.

Probably not making a difference in this case, but letting you know.

 

[JonHornsby]

Uh, oh.

We failed to lock the mirror - never occurred to me to do that. So that was a flaw in our test procedure.

As you say, it may not have biased our test results but I sure wish we HAD done that.

Thanks.

 

[JerryPH]

I bet that, considering all that was done, that this would not have changed things much. If you have the camera still, you can give it a go, its not that long to do, but if you have already gone to another camera, don't bother and just move on.

Personally, I am the curious type and would try it, just for the sake of the fun of testing.

Out of curiosity, how many shutter actuations are on the camera in question? That could also be a factor... a well used unit would have wear issues that could cause just that.

 

[Mike_E]

One of my favorite lenses is a Tokina 28-80mm f/2.8. Most Canon shooters I've ever heard disliked the lens but practically every Nikon shooter loved it. (of those who used it of course)

Focus was always the complaint among the Canon shooters.

 

[JonHornsby]

JerryPH and Mike E --- Insofar as I know there is only one button to physically actuate the shutter, the "regular" button you push to take a picture. This same button activates the self timer. Hopefully, I have not misunderstood your question.

And that's interesting ("suggestive") about the focus complaints with the Tokina lens on the Canon.

 

[JerryPH]

One of my favorite lenses is a Tokina 28-80mm f/2.8. Most Canon shooters I've ever heard disliked the lens but practically every Nikon shooter loved it. (of those who used it of course)

Focus was always the complaint among the Canon shooters.

Well to be honest, Sigma has some issues with consistency and quality control. When they get something right, it is incredibly right... reverse is true too. They have a bit of a bad track record with some lenses and QC.

Honestly, I sincerely doubt that mirror slap was so bad that it would cause this level of blur. That would have to be a seriously instable tripod... lol

The fact that this happens on more than 1 lens also points the finger at the camera. That is why I was asking about actuations. A well used camera would have a lot of loose parts and could cause these fluctuations in focus. XT or XTi's are not really made to go much over 50,000 actuations without issues.

 

[Dao]

If you are still interested in doing more testing, this site is pretty helpful.


Nikon D70 Focus Chart

 

[JonHornsby]

Oh, excuse me, JerryPH. I didn't realize what you meant by actuations. I would guess the shutter had been pressed maybe a couple of thousand times over the past two years.

And thanks, Dao, that looks very useful. But since Jenny has now sold the camera, I won't be pursuing testing for the Rebel Xt. However, I will save this on my hard drive for future tests, should the need arise.