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 p.2 #20 · 85L II unrealistic expectation? | |
BrianO wrote:
yauyi wrote: ...average about 8 out of 10 shots are OOF, they weren't front or back focus....simply out of focus.
I'm not sure what you mean here; an OOF subject must be the result of the focus being either in front of or behind the subject plane; if it were neither front focused or back focused, then it would be focused.
As for why this is happening, I suspect it has more to do with how much of the frame is filled with the subject, rather than the actual distance to the subject.
Another possibility is that you're tripping the shutter before focus has been fully achieved; the 85L has a lot of massive glass to move during focusing. That would be affected by distance, and longer distances could slow things down a bit.
What focus mode and focus point settings are you using?
yauyi wrote:I get the focus confirmatin beep before pressing the shutter though. was using single shot with center AF point. I thought on longer distance subject the bigger DOF would have enough coverage to get the subject's face in focus...since there's where I aim at, no?
My experience with the 85L (have used it for many years) is that it has some field curvature, meaning the plane of focus is not perfectly flat. It tends to focus a bit closer at the edges than the center. So if you're using the center focus point and recomposing, you might find that the middle of your photo is focused but the extremes (like where a subject's face might be) are slightly soft.
Look here: http://www.slrgear.com/reviews/showproduct.php/product/354/cat/10 and click on Full-Frame Results. Click on the graph to open it in a new page and move the aperture slider. You'll see that wide open the lens is sharp in the middle, but falls off to the edges, my guess being in part due to the field curvature. The lens can be focused sharply off-center, but you'll need to do so with a non-central AF point of try to manually focus it. My suggestion would be to try live view at 10X (a pain to do hand held, but still doable). The only catch with live view is that with very fast lenses the camera will stop down the lens in bright light to moderate the amount of light reaching the sensor. The way to prevent this is to either use depth of field preview for your actual shooting aperture, or change live view to movie mode, where it is forced to work at the actual shooting aperture *but* this is only if you set exposure manually (these instructions are based on using live view on a 1DIV, which I expect to be the same as the 5DII, but might not be).
Kolor-Pikker wrote:
Seeing as you're using a 5D2... you weren't using any points other than the center point, were you? The outer points aren't very reliable, it's probably better just to focus & recompose.
I've now gotten in the habit of using the "sports shooter's" layout with the camera in AI servo and using the AF-on button to focus as it makes the 85L more manageable. Continuous shooting is a good idea too.
And do you have an Eg-S focusing screen as well? The standard focusing screen in most cameras lets you see the effects of DoF only down to f/2.5, so a percision screen is very recommended for fast primes, especially the 85L.
yauyi wrote:I would have to give AI Servo a try on longer distance subject and see if it helps and look into the Eg-S focusing screen....
I would highly recommend you look into the Eg-S. I found it made a huge difference back when I first got the lens and was working with the 1DII series. That stock screen would smear the image too much but I could easily discern accurate focus with the S screen. The S screen will result in a darker viewfinder image with slower lenses but IMO it's still OK at f/2.8 but f/4 will be fairly dim. Not a problem outside, but could be inside. One other catch I've heard is that the 5D series may not be as precisely set-up for accurate manual focusing and might require calibration by shimming the focusing screen... but it's worthwhile for you to try the screen first to see if it helps.
It definitely helped me, but mostly for closer working distances. For full length type shots I still had trouble (could be my eyes) and find the most accurate solution is 10X live view.
martsmith42 wrote:
The outer points aren't very reliable, it's probably better just to focus & recompose.
There is a steep learning curve with the 85 f1.2. You can't focus and recompose at f1.2 as it will result in oof shoots. the d.o.f is toooo shallow
according to the DOF calculator, 15ft @f/1.2 I'd get 0.67ft DOF....which is significantly greater than at 5ft subject distance with only 0.07ft DOF...
It's DOF, not critical point of focus. There is a difference. And as I've mentioned, the lens seems to have a bit of field curvature that could pull the plane of focus away from the subject.
Ron
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those like 5, 6, and 9 is about 75% which is acceptable I think.