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purple highlights

J

Jamesmd

Guest
here they are

first without vu filter
second with vu filter
 
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J

Jamesmd

Guest
:thumbup: much better , yes Sir . that was with color , no ? I tried moire and didn't work.
thanks !!

so I can fix it , but , what about the lens , should it do that ?
 

douglasf13

New member
Hey James, I'm a little confused. Are you saying that the CA is worse with the UV filter, or without? The labeling on the pic you posted contradicts the statement you made prior to it. Thanks.
 

Eoin

Member
James,

From what I know with the ZA 85, if you blow the highlights (overexpose the brightest part) you will see this purple fringing or what others call sensor bloom. Reason being there is too much light hitting the sensor in the area of the highlight. The best advice I can give or suggest is you try different exposures of the same scene where you reduce each exposure by 1/3 of a stop and see if the purple will disappear for you.
 
J

Jamesmd

Guest
sorry , it was worst with the filter on.

I have been shooting the same pic with CZ 85 1,4 and SONY 50 1.4 an they do the same , from 1.4 to up to 2.8 or so .
Could a couple of different persons do the try please ?

grrr ,nothing worst than thinking your camera might be wrong , it can drive you nuts :( :confused:
 

douglasf13

New member
Well, maybe I'm not crazy after all :eek: That is exactly what I noticed in my very basic tests last December with filters on and off using those two lenses. It looks like we need some more exacting tests on the matter.

I don't think there is anything wrong with your camera. It's just the nature of the beast.

p.s. you may want to edit your pic post so people don't get confused :)
 
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Eoin

Member
With large aperture lenses you are always prone to this, there is a fine line between a correctly exposed image and one where you get this purple fringing. I would think there is nothing wrong with the lens. But leave the filter off for the moment.

I know my favorite lens of all time, the Canon 85L used to do this quite regularly until I began to understand what effected it. Sometimes the dynamic range is just too much for the sensor to handle and you need to make a decision what you want, highlights or shadows and shoot accordingly.

Another thing you may wish to do with Aperture is turn down the Boost (50-75%) in the raw fine tuning brick. then learn your camera's exposure meter, Douglas has some settings you can use with the creative styles, neutral setting with -1 saturation, -3 brightness and -1 zone. This will I believe get the histogram to correctly or in as near as possible reflect what the RAW exposure is like and not what the in camera jpg is.

Then you can use the RGB histograms on the back of the camera to see if you are clipping the highlights. I know it's frustrating, but you need time to understand and evaluate what's going on and how best to use the indicated camera exposure meter with what is actually going on in the raw file.
 
J

Jamesmd

Guest
Thanks so much Eoin . I'll do exactly all you said and , practice , practice and practice .
Cheers .

James
 

douglasf13

New member
Eoin is right on. Longitudinal CA isn't uncommon in wide aperture lenses, and overexposure can be the culprit. However, remember that most scenes require the overexposure of specular highlights in order for the rest of the scene to be exposed correctly, so you'll probably have to except some CA lots of times in those areas, and hopefully it is either unnoticeable or removable if it bothers you. You don't want to get into the practice of not blowing any of your speculars, or you'll end up with really dark, noisy pics. Jeez, that's a lot of double negatives. Sorry. :eek:

The UV filter thing may be an interesting development.
 
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J

Jamesmd

Guest
for the tests I'm doing , the thing is avoid great dynamic range under F 2 and everything seams ok .

Thanks guys .

James
 

fotografz

Well-known member
I've just done the same shot with and without VU and its worst with.

Ill send pics right now .

Can you do similar test to se if you have it ?

its 100 ISO , 1,4 F .
This proves nothing. The two photos are different. Look at what is in focus and is not between the two images.

LoCal shows up in the OOF Bokeh ... and the second shot is more OOF which has nothing to do with the filter.
 
J

Jamesmd

Guest
Fotografz , you are right .I'll do them propperly with tripod and manual focus for conditios to be the same .

Thanks braeside .

Cheers

James
 

douglasf13

New member
Yep, that's why I said "maybe" I'm not crazy :) Tripod test with the same lighting conditions needs to be done on multiple scenes.
 
J

Jamesmd

Guest
ok , here is the test .

the pics on the left without VU it says anyway .

I think it means that filter doesn't change things and that CA disappears at f 5,6 +/-.

Hope its any good .

Cheers

James

PDF to big !!! ill have to do something :(

just a sec
 
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