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Archive 2012 · 7D MA direction??
  
 
drbob
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p.1 #1 · 7D MA direction??


Search has been unsuccessful for this dumb question.

7D micro adjustment window:

camera _______________ subject _x_______________ Infinity
- +

If my camera appears to be back-focusing, (x), do I dial in - adjustment (moving the focus point closer to the camera... or a + adjustment? Intuitively, I think it should be - for back focus, but want to be sure how others interpret this.

My reading of TFM has not cleared this up for me.

thanks,
bb



Jan 28, 2012 at 06:08 PM
gspiridakis
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p.1 #2 · 7D MA direction??


You should move it to -.
What i am not sure, is if the MA works accurately always.
I had a 50D and a 400 f/5,6L in the past. I coulnd't get very sharp results even under ideal conditions. My friend with also a 50D and a 100-400 and his results was like mine..I was sure that the fixed 400 should get sharper results. I did the MA, and i found that the lens was back focusing. At -6 my photos were sharper indeed. The problem is that when i was shooting in differnet distances (much longer or too close) than the distance i made the MA, my results were less sharp again..
I am not sure if it was my camera's problem, or the lens', but i noticed that MA was not working the same in all distances...
I may be wrong, i don't know for sure, but an other friend also told me the same once, and i wonder if anyone else had the same experience...

Bob, sorry about asking in your post, if you mind i could write it on a separate topic..
George



Jan 28, 2012 at 06:28 PM
BrianO
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p.1 #3 · 7D MA direction??


drbob wrote:
...If my camera appears to be back-focusing, (x), do I dial in - adjustment (moving the focus point closer to the camera... or a + adjustment? Intuitively, I think it should be - for back focus...


Your intuition is correct.

If the camera is back focusing, it's focusing too far away; so you want it to focus closer. A minus adjustment brings the focus closer.



Jan 28, 2012 at 06:29 PM
BrianO
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p.1 #4 · 7D MA direction??


gspiridakis wrote:
...What i am not sure, is if the MA works accurately always. ...I did the MA, and i found that the lens was back focusing. At -6 my photos were sharper indeed. The problem is that when i was shooting in differnet distances (much longer or too close) than the distance i made the MA, my results were less sharp again...


Hopefully even though the other distances weren't as sharp, they were sharper than with no MA at all.

If you have one distance range that you use more often than others, doing the MA at that distance is best. A birder might always take pictures of distant subjects, for example, while a portraitist might always take close-range shots.

For someone who uses the entire near/far spectrum, many people suggest doing the MA adjustment using a test target at a distance of 50-times the focal length. So for a 400mm lens, for example, you'd place the test target at 400 X 50 = 20,000mm = 20m = 65 feet.



Jan 28, 2012 at 06:42 PM
gspiridakis
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p.1 #5 · 7D MA direction??


For someone who uses the entire near/far spectrum, many people suggest doing the MA adjustment using a test target at a distance of 50-times the focal length. So for a 400mm lens, for example, you'd place the test target at 400 X 50 = 20,000mm = 20m = 65 feet.

Thanks Brian, i didn't know that.
And yes you are right about the other comment also, ,
but when you know that this is not the best quality your glass can take, you become annoyed about it..For me at least, i was dissapointed when in different distances my lens didn't deliver the best..
George



Jan 28, 2012 at 06:59 PM
BrianO
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p.1 #6 · 7D MA direction??


gspiridakis wrote:
...when you know that this is not the best quality your glass can take, you become annoyed about it..For me at least, i was dissapointed when in different distances my lens didn't deliver the best..


I completely understand, especially with high-priced glass like that.

I'm not sure, but I think when Canon Service recalibrates a lens there are different calibration factors programmed into the lens' chip for different distances; a more advanced form of "MA" than we can do in our cameras.



Jan 28, 2012 at 07:24 PM
 

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TeamSpeed
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p.1 #7 · 7D MA direction??


The way I remember it is that + values puts greater distance between you and the plane of focus, and - brings it closer to you. Also another technical point, each mark is 1/8 the DOF.


Jan 28, 2012 at 09:41 PM
okafoja
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p.1 #8 · 7D MA direction??


MA is a total waste of time. You solve one issue and create another one. Send your camera to Canon.


Jan 28, 2012 at 09:55 PM
RobDickinson
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p.1 #9 · 7D MA direction??


Whats the other one?

MA works. Tolerances arnt tight enough to provide perfect focus for every lens on every body.



Jan 28, 2012 at 10:00 PM
BrianO
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p.1 #10 · 7D MA direction??


okafoja wrote:
MA is a total waste of time.


I think yours is not a widely held opinion. I can guarantee that I don't agree.



Jan 28, 2012 at 10:08 PM
Imagemaster
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p.1 #11 · 7D MA direction??


BrianO wrote:
I can guarantee that I don't agree.



Great line.



Jan 29, 2012 at 12:56 AM
Jeff
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p.1 #12 · 7D MA direction??



okafoja wrote:
MA is a total waste of time.


BrianO wrote:
I think yours is not a widely held opinion. I can guarantee that I don't agree.


I'll go one step further and say most of his opinions are not widely held.

Of course, YMMV...



Jan 29, 2012 at 06:42 AM





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