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jurgen

GH4 stills - strange RAW pixel behavior/artifacts

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Might be an overanalysis, but I've been shooting a lot of stills on my GH4, and because I normally edit in ACR+Photoshop (for which there is no GH4 RAW support yet), I've pretty much been jpg's only to this point.

I decided to give Iridient and PhotoNinja a go earlier today, and I had some strange discoveries.

In both programs, at between 100% and 200% view, there are what looks like dead pixels throughout the frame (maybe 10-15 scattered across).

They look like this:

http://imgur.com/FxCJ8rl
http://imgur.com/5H2RGHU

And at first I thought I just needed to run the pixel remap, which I did a couple times, to no avail. All spots still there, still in the same position. So then I started to worry that maybe I had a serious dead pixel problem which would show in video, so I shot a bunch of different stuff at 4K, cropped way in, and the image was clean as a whistle.

So then I got curious, and I started downloading every other RAW GH4 photo that I could find (a whole range of ISO's and shutter speeds) from five different sources, including a couple Spanish sites and imaging-resource.

Here's what I found on imaging-resource, and every other site:

http://imgur.com/h1sMlyG

 

Link to download: http://www.imaging-resource.com/PRODS/panasonic-gh4/panasonic-gh4A7.HTM

 

Every single RAW photo from six different GH4's has this black "noise" in it, at shutter speeds from 2 seconds to 1/8000 and ISO's from 200 to 3200 (high as I looked). It looks like dead pixels, and it responds to the dead pixel filter tool in Iridient, but it's weird, because it's pervasive throughout every single photo from every camera I've seen. Is it possible this is an artifact from the GH4's image processing, or perhaps a hitch in the way Iridient processes images? For what it's worth, some of these spots (though not all) also show up in Photo Ninja - this is, again, true for all six cameras, every single photo.

Any thoughts, anyone?

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Download a exif editor. Open the GH4 raw files and change the camera model flag to GH3 or GX7. Now you can open then raws in ACR. See if you get the same problem.

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Download a exif editor. Open the GH4 raw files and change the camera model flag to GH3 or GX7. Now you can open then raws in ACR. See if you get the same problem.


Trying to. I've got ExifTool running on my MacBook and for some reason the commands keep kicking back errors.

exiftool -model="GH3" *.RW2

kicks back a "FILE NOT FOUND" error message.

Any ideas?

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I'm using ExifTOOL GUI so I don't have to bother with the command line. Not sure if that's available for Mac. If you upload some raw files (wetransfer.com - send it to yourself, paste the link here - or dropbox etc) I can convert them and re-upload them.

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Curious! Just downloaded the same file. In Iridient, all the black spots are still there.

Hmm. Maybe it's an Iridient thing, as I've been thoroughly mocked elsewhere for not assuming from the get-go.

Thanks for your help, Julian!

Also, as a quick aside - any harm in running pixel refresh more than once? I've done it a couple times and while I can't see any harm in it (or imagine there being any), the thought just crossed my mind that maybe it shouldn't have been done.

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That's been suggested elsewhere, but I don't think so, as they're randomly assorted camera to camera (though always in the same spot for each particular camera).

At this point, I'm pretty convinced it's artifacts introduced by various RAW developers.

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@jurgen: I think pixel refresh is a software thing so it won't do harm. Not 100% sure though.

 

The black pixels 'might' be really there, could be that ACR automatically fixes it. Maybe try with some GH3/GX7 files if you get the same artefacts?

 

Can't be autofocus pixels, the GH4 doesn't have any I think so? Contrast AF only (with the new DFD system, that is more like an algorithm?) no phase detection focus pixels.

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I just did a 600% punch in on 4K video - no problems, clean image.

ACR might fix them automatically, but the strangest part of this to me is that it's not a one off thing - they show up in every GH4 RAW photo on every camera I've seen.

I'll do some more looking around, and keep an eye on it with my own copy.

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Flower picture from photographyblog.com's review:

http://www.photographyblog.com/reviews/panasonic_lumix_dmc_gh4_review/sample_images/

http://imgur.com/yZW5P4H
http://imgur.com/FMFCwPG
http://imgur.com/RmMT2dA

These are just cherrypicked from around the frame, there are probably 20-30 spots I counted scanning at 100%. This was an image shot at 1/400 at base ISO. (viewed in Iridient - it's in every other photo I looked at on there as well).

Again, I don't think this is a big issue, but ... weird that it's in every copy, at least when viewed in Iridient.

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my first Panasonic G6 had dead pixels on the sensor straight out the box - I had to send it back and get a replacement

the replacement was fine

my dead pixel issue looked like your problem does on your pictures

 

it does happen so consider returning it

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my first Panasonic G6 had dead pixels on the sensor straight out the box - I had to send it back and get a replacement

the replacement was fine

my dead pixel issue looked like your problem does on your pictures

 

it does happen so consider returning it

Most of these aren't my pictures, but pictures from six or seven different GH4 RAW samples around the internet (imaging-resource, photographyblog, quesabesde, etc.) They show up in every GH4 RAW photo I've seen, making me think that either something is happening with Iridient, or something has changed from the way the GH4 handles RAW photos in camera.

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I'd wait for proper raw support before making any conclusions.

 

Did you try with GH3/GX7 files? I'm curious if it shows the same. Might be a software problem.

 

Maybe send Iridient an email, they might have a clue why this shows up.

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Have already asked him:
 

"Most modern digital cameras these days do a very good job automatically mapping out dead pixels prior to the RAW image data even being stored to file. In my limited tests so far with the GH4 I didn't find obvious dead pixel issues, but may have misse them, and I assumed it was doing a good job with this internally.

Many RAW processors always automatically do dead pixel filtering, in Iridient Developer for various reasons (most cameras don't need it, it's nice astrophotography to be able to turn such filters completely off, etc) by default I typically do not.

See the Detail pane in the Settings window of Iridient Developer where there are adjustable levels for the "Dead Pixel Threshold". If you set this filter to High, this likely will clear up any such issues.

I'll do some further investigation into this and perhaps will turn on the dead pixelfiltering for all images from the GH4 in a future update.

Best regards,
Brian Griffith (author of Iridient Developer)
Iridient Digital

And he may very well be correct - on an E-M1 or 5D, for instance, there may be some sort of dead pixel filtering before RAW data is ever saved. But either this isn't happening or something is wonky with Iridient's profile (and PhotoNinja's as well, as some of the spots [but not all] appear there as well). If it were only my camera I would say, okay, dead pixels, send it in for warranty. But it's not - it's every GH4.

So that, to me, is the curious part.

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I'd wait for proper raw support before making any conclusions.

 

Did you try with GH3/GX7 files? I'm curious if it shows the same. Might be a software problem.

 

Maybe send Iridient an email, they might have a clue why this shows up.


Just downloaded and opened a GX7 file (1/500 shutter speed, ISO 200).

Much to my surprise:

http://imgur.com/BkBdBYe

"Dead" pixels, or ... something.

I think something is amiss with the way that Iridient processes RW2 files. It doesn't make sense that literally - without a single exception - every single Panasonic RAW file I've opened (on Iridient across two separate computers) has shown these black dots.

Good thinking, Julian.

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