tom_bone

<p>Marcus: Thank you for your comments. Unfortunately, there is no "stills + movie" function in LV for the T2i so there is no real way around the lens shift that I can think of with my camera. </p> <p>I also thought of using the DOF preview button - as you suggested - but I didn't notice the lens shift. I was surprised, I thought I would.</p> <p>As I mentioned, I will send my lens to Canon for analysis and, hopefully, repair. It is too bad about the lens shift, it is otherwise a very beautiful lens to work with.</p>

<p>Robin: I may be mistaken, but although wide open (2.8) allows light from the edges of the lens to hit the focal plane, it has little to do with how the edge and the centre of the image look.</p> <p>What it happening with lens shift is that the light entering from the edge of the lens converge at a different point than those entering the centre of the lens, this means that the point of focus (circle of confusion) will appear differently than when stepped down (when the edge rays have been eliminated). Basically, the point that looks sharp at 2.8 is different from the point thaat looks sharp at 6.3. The end result is that when you focus at 2.8 you end up focusing in front of the point that would have looked in focus at 6.3.</p> <p>This is difficult to describe without a diagram, I have found a useful one here: http://photographylife.com/what-is-focus-shift <br> By the way, my lens is version II.</p>

<p>The distance to the object was between 18" and 24" (I have since taken down my set up so the distance is approximate). I can tell you that the focus shift was large enough to render it a useless image. Godd thing I had my 100mm with me to do the job.<br> The other thing to mention is that the shift was larger the narrower the field of view, so 70mm was more pronounced than 50mm, and so on.<br> I am still using the lens day to day for some video work so I cannot send it in to Canon for servicing until next month. I am hoping this is something they will be able to adjust.<br> If anyone has ever sent in their lens for "residual spherical aberration" repair I would be interested to hear about your experience.<br> Tom.</p> <p> </p>

<p>Is there a known cure for residual spherical aberration?</p> <p>If I send it in to Canon, would they be able to adjust it or is it something that is fundamentally flawed in the design of the lens or in the particular components that make up mine?</p>

<p>Robin: No, it is not a shutter speed issue, as I mentioned, the objects behind my focal point are sharp. The lens is clearly back-focusing. I was under the impression that back focusing is only an auto-focus issue.<br /> Given the fact that I am manually focusing and that there is a different in focal plane from 2.8 to 6.3, I think this is a question of focus shift that I am not picking up on with live view.</p>

<p>I am manually focusing on (relatively close) stationary objects with 10x magnify mode on the LCD. I do not have MA on my camera.<br> Upon further testing, I have noticed that at 70mm f2.8 the image is sharp; at f6.3 (and higher) the image is off (back-focusing). So something is happening in between.<br> The only way I can explain this to myself is that my lens suffers from focus shift as I step it down from 2.8 to 6.3 and that the Live View LCD image is always 2.8 - regardless if the camera is set to something smaller.</p>

<p>Hello Everyone,<br> I am new to photo.net though I have been visiting the site for a long time.<br> I am posting because I am having issues with my Canon 24-70mm f/2.8 L lens I purchased a few months ago. Until recently, I have been using it with a C100 with no problems. Yesterday I attached it to my 550D and experienced focus issues.<br> Perched on a solid tripod, zoomed to 70mm, while focusing manually on a particular object in live view, the LCD looks tack sharp, but the object in the photo is blurry. However, I can see that an object behind my focus point is tack sharp.<br> In other words, the actual plane of focus was further than what I has focused manually on.<br> To test this, I tried focusing in front of my object (so that it looked blurry in live view) and the photo turned out sharp.<br> Frankly, I am stumped. I thought live view was what the sensor was actually seeing. Can anyone explain to me what is actually happening? and what I can do about it?<br> I don't seem to be having this problem with the C100, but I am not 100% certain.<br> Thank you very much for any assistance.<br> Tom.</p>