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Old Sep 25, 2013, 6:17 PM   #1
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Default Can't get focus sharp

Okay, guru's I've been working on this one for a while and it's time to stop beating my head against the wall and turn to the experts.

I cannot get this "system" to focus sharp.

I have a Canon 5d Mark iii mounted to a Canon 2x Extender, mounted to a Canon 70-200 2.8 IS lens with a Hoya CPL filter on it.

I trying to shoot in really bright sunlight.
I'm shooting at the full 200mm (or 400mm if you include the 2x magnification).

Is there a way to make this work?
Should I use stabilizer mode 1 or 2?
Should I use 1.4m to infinity or 2.5m to infinity

(or the best answer, can you talk my bride into letting me buy a 400mm lens?) Just kidding on the last part. That's mega money.

Is there a way to make this set up work or am I just wasting my time.

As always, thanks for your help and thanks for making me a better photographer.

Faithfully Yours,
The Faithful Pastor
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Old Sep 26, 2013, 3:21 AM   #2
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hi can we see an example with exif data please.

next try this put the camera on tripod and take a shot of something with just the 70-200, then add the filter and finally the the converter see where the problem lies.
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Old Sep 26, 2013, 6:47 AM   #3
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Can you get good focus without the extender?

Do you have a tripod? Can you get good focus when using it (and the self-timer, and a remote release if you've got one)?
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Old Sep 26, 2013, 12:19 PM   #4
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Default example

Here's one of the photos.
It was shot at 6.4f
1/1000
iso 200
200mm x 2 = 400 mm.

This photo is not cropped. The center focus was the mailbox.
I used a timer and mounted it on a tripod.

FP
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Old Sep 26, 2013, 12:30 PM   #5
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Default 2x extender removed

On this photo, I have removed the 2x extender, but left the filter in place. I used a timer and a tripod.

3.5f
1/1000
ISO 100
135 mm
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Old Sep 26, 2013, 12:35 PM   #6
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Default no filter

No filter
5.6f
1/1000
135mm
100 iso

Thanks again!!
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Old Sep 26, 2013, 1:19 PM   #7
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Default filter problem

From looking at these photos, the problem seems to be with the filter.

Why would a CPL filter cause this kind of focus issues?

Thanks!

FP
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Old Sep 26, 2013, 4:10 PM   #8
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Are you sure it's a CPL? (... a Circular Polarizing filter.)

Circular Polarizing filters were developed because it was found that Linear Polarizing filters, the type of Polarizing filters in use up to that time, interfered with Phase Detect AF systems.

From Wikipedia:
Quote:
Linear polarizing filters can be easily distinguished from circular polarizers. In linear polarizing filters, the polarizing effect works (rotate to see differences) regardless of which side of the filter the scene is viewed from. In "circular" polarizing filters, the polarizing effect works when the scene is viewed from the male threaded (back) side of the filter, but does not work when looking through it backwards.
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Old Sep 26, 2013, 4:21 PM   #9
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Hi TCav,

The side of the Hoya Filter says 77mm CPL. So it's either a Circular Polarizing Filter or a Corporal in the Marines.

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Old Sep 26, 2013, 6:58 PM   #10
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G'day FP

I accept that it is a Hoya CPL mate - no issues there

Upon reading the line in the original post giving the list of optics used, I reacted that it was the filter ... I have had several users recently come [incl myself] to come thru with furry images from Hoya filters

In my case, my Hoya CPL is made in the Phillipines and gives me heartache - paid $99 for it and am very disappointed in both sharpness & the CPL abilities as well

I have had workshop students with CPLs where the use of the CPL does both of make the image slightly blurry & also adds a silvering effect to the image - can't answer why to either bad effect

Hope this helps a bit
Phil
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