Avoiding Chromatic Aberration?

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Ron Jackson
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I recently purchased via e-bay a "Century Optics 1.6x teleconverter" for my Canon XLH1 standard 20x zoom. Got it for £115.

This TC has a tendency towards C.A (as indeed does the 20x lens itself) which is a pity because it is a nice bit of kit even when used with my Canon 1.6x TC designed for their XL cameras.

Is there a way I can mitigate or limit the effects of C.A.? I know I can "avoid" by not using the TC but it is otherwise very useful.

I do notice that C.A. appears more pronounced when the subject has light edges against a dark background and vice versa e.g a white bird against dark rock or a dark bird on water. More pronounced too at maximum telephoto. Less noticeable in shots with a bit of under exposure.

I don't think that there is anything that can be done in post, unlike with stills shots.

Handy to know if there are shooting techniques that can help.

Ron

Ron Jackson

Gavin Gration
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Would an EOS adapter/lens be a better solution?

Ron Jackson
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I've got an EOS adapter and lenses as well. The 20x plus TCs gives power zoom over a wide range (I hardly ever zoom and record simultaneously) plus auto focus which can be useful in wildlife filming. Built in ND filters also useful.
Image quality on my 70-300 "L" Canon lens is better than 20x plus TCs, once I get the focus spot on, but as said there are some advantages with the TC outfit.
(Looks as if Canon have given up on 1/3 chip interchangeable lens cameras, otherwise I'd be asking them for a mini broadcast 20x or even 40x lens with built in 2x TC)

Ron Jackson

Alan Roberts
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In that chromatic aberration happens in the lens, there's sod-all you an do about it once it's recorded. Some recent cameras have correction in-camera, but that's only for high-end kit. There are aberration corrections in some graphics software (I think Photo Shop does some, and Paint Shop Pro, but I'd have to check on that), but it gets really tedious doing it.

Get my test cards document, and cards for 625, 525, 720 and 1080. Thanks to Gavin Gration for hosting them.
Camera settings documents are held by Daniel Browning and at the EBU
My book, 'Circles of Confusion' is available here.
Also EBU Tech.3335 tells how to test cameras, and R.118 tells how to use the results.

MAGLINK
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Joined: Mar 8 2007

The CA correction on my HPX301/371's works very well but I never go above f5.6 and generally stick around f2.8 as recommended.

I did put a wide angle adaptor and filter on and they both increased it substantially so I ten to shoot with them off most of the time, you could try adding a circular polariser filter and see if that improves the CA when the wide angle is added.

Ron Jackson
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Thanks all. I did have an idea that I was to a large extent "stuck" with CA, mitigated to an extent via the points I mentioned. Gary's idea re a polariser is interesting (my "Century" is a Tele-converter rather than Wide-angle adaptor). Probably a 105mm polar will cost me more than the TC did, in fact I've an idea they are bespoke to Century/Schneider.

Ron

Ron Jackson

Alan Roberts
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I don't think a polariser will make any difference.

Get my test cards document, and cards for 625, 525, 720 and 1080. Thanks to Gavin Gration for hosting them.
Camera settings documents are held by Daniel Browning and at the EBU
My book, 'Circles of Confusion' is available here.
Also EBU Tech.3335 tells how to test cameras, and R.118 tells how to use the results.

Ron Jackson
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"Judicious use of my Tele-Converter" seems to be the conclusion. I can understand why pros and pro outfits spends lots on big monitors so they can see what is going on before it is too late. My little (but cost more than a 50 inch 3d plasma) Swit 4.8inch monitor okay, just, for focussing and composition but not really for checking image quality as recorded to the CF card.

Ron

Ron Jackson

Ben Longden
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Joined: Jun 10 2009

Only half decent optical design in the lens can fix CA...