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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 06 Feb 2009 (Friday) 01:45
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How to do a focus test chart with a 400 5.6

 
realitysays
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Feb 06, 2009 01:45 |  #1

Hey guys,

I know it might sound like a stupid question:o

But how do i check if my 400 5.6 is back focussing/front focussing?

Everytime i do it with the MFD at 3.5 and aperture wide open at 5.6 it seems that because its so far away and the aperture is not that wide that it gets to about 20-30mm back and front before the bokeh comes in.
It appears that the black line also does not seem to be tact sharp either.

Any help or suggestions how to make this easier? Shoot further away? If i do this it won't fill the frame but..


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actprivate
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Feb 06, 2009 03:05 |  #2

You are talking about the black line. Not sure if you mean you are already doing some sort of test or not. However, below is a link to one of the popular methods for focus test. I have tested all my lenses with this method. Hopefully it works for you, too. You need to follow the instructions in the document and get a print out of the chart to carry out the test. Remember to keep the 45 degrees, mirror lock up (if slow speeds) and tripod in mind.

http://www.focustestch​art.com/focus21.pdf (external link)


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xarqi
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Feb 06, 2009 03:39 |  #3

Tricky.
The test should be done at 50 x the focal length, or 20 m in your case. At f/5.6 that will give you half a metre of DoF, so you'll need a very big chart.

Try putting about 20 small road cones in a line half a metre apart in a car park, and standing slightly off-axis and 20 m away, focus on the middle one. This is the "battery test" on a large scale.




  
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GyRob
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Feb 06, 2009 07:16 |  #4

xarqi wrote in post #7265691 (external link)
Tricky.
The test should be done at 50 x the focal length, or 20 m in your case. At f/5.6 that will give you half a metre of DoF, so you'll need a very big chart.

Try putting about 20 small road cones in a line half a metre apart in a car park, and standing slightly off-axis and 20 m away, focus on the middle one. This is the "battery test" on a large scale.

could use 20 car battery's :lol:
that said the cones or that sort of thing is a very good ider .
Rob


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xarqi
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Feb 06, 2009 07:21 |  #5

GyRob wrote in post #7266261 (external link)
could use 20 car battery's :lol:

Tee hee :)




  
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Jack ­ Dawe
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Feb 06, 2009 07:23 |  #6

Or maybe find a long fence with a lot of vertical bars?


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xarqi
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Feb 06, 2009 07:23 |  #7

Jack Dawe wrote in post #7266284 (external link)
Or maybe find a long fence with a lot of vertical bars?

Good thinking. Probably best to place a target on one "picket" to avoid confusion.




  
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How to do a focus test chart with a 400 5.6
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