GH5 Issue with GH5 color shifting while focusing the lens, Strange!

tokun1

tokun1

Well-known member
Hello Group!

I'm having a VERY strange new issue now with my GH5. I've had the camera for 2.5 years now and never experienced this. So, I'm shooting at the moment with my new Veydra mini prime all manual lens in a very well lit room. I set the white balance manually and am shooting at 24p 1080 and I'm noticing after shooting close up and previewing the footage on my large Imac, that the color is shifting and changing color as I'm focusing in and out and along the subject (in this case my cat). It is as if I can see the focus peaking moving as it is focusing but with a slight color shift and this happening as I focus in and out the color shifts slightly. I only notice when shooting close up and watching after importing into FCP. I can't see anything in the LCD, just the blue focus peaking which I have set to low. I tried to reset the camera and it's still happening, and I also did test it with my native Panasonic Leica 42.5mm mft lens to make sure it wasn't the Veydra manual lens and unfortunately I get the same issue. I tried shooting several different color profiles, standard, cine d and V-log all with the same issue, however I did notice the issue is more prominent than the other color profiles when shooting in Vlog!

Has anyone else had this issue when shooting on all manual lenses or other lenses, And, if so can you suggest what to do?

Thank you for your suggestions!
 
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Also make sure you're shooting in the video M mode and not PSAM on the dial. Shooting video in any of those modes on the dial besides videoM with have nearly everything auto including white balance.

Just a thought anyway why you're seeing it all of a sudden.

Cheers, Pete
 
Thanks for your reply! Great suggestion and great point as that happened the last time I was trying out a new manual lens, I had it on auto white balance and it did have some major color shifting, but I'm shooting all manual. It's only when I focus across the subject, again very odd and very frustrating.
 
Thanks for the reply Pete, yes I'm shooting in the video M mode and all manual everything.
 
Might need to upload the original file to rule out any software problems since you mentioned it doesn't appear on the cameras LCD.
 
Thanks for the reply, I just can't see it on the LCD because it is small and the color shift is subtle. Where do I upload the file to, here on DVXuser?
 
You'd need to use something like Google drive and list the shareable link. This way we can rule out if it's just your system or the GH5.
 
tokun1 said:
Has anyone else had this issue when shooting on all manual lenses or other lenses, And, if so can you suggest what to do?
Click to expand...

I think most of us have seen this problem throughout our working lives. Generally it happens with wider aperture lenses and when working at closer distances. You just have to work around the issues. Stopping down and increasing focal distance or even using using longer focal lenses will all help to mitigate the problems seen. Quote:

"Spherical lenses, those whose radius of curvature remain constant from edge to edge, are subject to various types of optical aberrations. These aberrations are not caused by defects in materials or manufacturing techniques, but rather by the laws of optics themselves."
https://escooptics.com/blogs/news/84510147-chromatic-aberration-in-spherical-lenses

Another thing that can compound the issue you describe is the precision and quality of the spectral filter array on the Bayer sensor which alternates red and green filters for the odd pixel rows and green and blue filters for the even pixel rows of the image sensor. The image processing procedure precisely determines the geometric distortions of the red and blue image pixels in comparison to the green reference pixel. Therefore a lot is also dependent on the quality of that spectral filter array on the camera's Bayer sensor along with the algorithms used in the de-Bayer process as they all go to influence the final image.


Now if you were to try the same experiment with your blower can at a much greater distance you would be hard pushed to see the same color shifts at say ten feet as opposed the distance used in your example. Any spherical aberration is going to be multiplied the closer you are. Especially at wider apertures on wide lenses as the amount of curvature of the light rays required to bend them into the sensor is at the extreme end of lens design. The phenomenon your are describing has been there all along I'm sure of it but sometimes it's only certain conditions that bring them to your attention. You mention your cat. Focusing across animal fur is a good example because of the myriad of small curved surfaces of high frequency detail that fur consists of will push even the best lens designs to the max for focusing the various wavelengths involved. All made to look worse as you roll the focus ring as all the different wavelengths encompassed in the light all have slightly different focus points at any given aperture at any given focus points. Even most modern auto lenses that have lens file information communication with the correction software in most modern camera bodies often can't fully correct all aberrations at all apertures at all focus points in any given source of light. That is a massive software task and would require massive look up tables to be embedded in the camera/lens file software. Very expensive broadcast 2/3" cameras have had issues like this for years. Canon and Fujinon's lens departments worked in conjunction with both Sony and Panasonic on their cameras and developed the ALAC and CAC lens correction circuits for their $30-40K lenses to work with the $20-40K camera bodies and still they haven't fully sorted the the problem by any means. Mind you trying to design a zoom lens that goes from the equivalent of FF 11.00mm with a 22 x zoom range is a very tall order.

You ask "And, if so can you suggest what to do? " Like most of us I think you'll have to learn to work around these sorts of issues, along with Moire and diffraction and all the other lovely things that can suddenly pop up to make shooting more difficult. A lot of good results comes from a lot of practice and experience and I'm still learning my way around theses sorts of things every day after shooting for too many years to bother thinking about. Lens aberrations problems have been around for ever. Check out this old bit of lens history if you are curious.

https://nvlpubs.nist.gov/nistpubs/bulletin/14/nbsbulletinv14n3p341_A2b.pdf

Chris Young
 
It is clear at 5 seconds in, from gray to green to pink/red color, watch it again you can't miss it.
 
Hey Chris, thanks for well thought out response and research info, that is a relief to know it's not the camera or lens as I thought it was my Gh5. I tested it with the my GH5s and with my cine lens and photo lenses with all the same result along with VLOG, Cine-D, Standard and Natural profiles too.
 
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