Panasonic GH4-vs-GH3, RAW ISO Image Quality

GH3 at ISO  12800 Crop

 

GH4 at ISO 12800 Crop

 

Executive summary--No difference

For those who want the details, read on. Although to be candid there is not much more to say.

I finally got my GH3 back from repairs yesterday. It had gone in to get a new EVF eyepiece lens as the original had become finely scratched from normal and careful cleaning. The Panasonic service contractor in Sydney, Definitech, was on the case but Panasonic was very slow to supply the required part.

Anyway the GH3 is like new now. The eyepiece optics may have been changed in mid production because the "smearing" problem initially reported on GH3 cameras is no longer evident.

So I ran my usual  ISO test comparing the GH4 with the GH3. I simply photograph a set of bookshelves with a section of newspaper advertisements for resolution testing, at each whole stop ISO setting.  The files were viewed in Adobe Photoshop Camera Raw 8.6, final version.

Results  I found across the ISO range that the two cameras used the same  aperture and shutter speed at each ISO setting.The GH4 files were darker with a left shifted histogram compared to the GH3. The amount I had to increase the exposure of the GH4 files to match the GH3 files with the slider in Adobe Photoshop Camera Raw was about 0.3 stops from ISO 100-12800.

The 25600 files from the GH4 were a bit odd. I had to give them 1.2 stops extra exposure on the PsCR slider to match the GH3 files even though both cameras used the same aperture and shutter speed. Across the ISO range the GH4 files were a little more blue and those from the GH3 a little more yellow, both using AWB.

All the files were evaluated side by side on screen at 100% after matching for exposure (brightness) and color as best I could.

At ISO 25600 the GH3 files showed noticeable magenta color shift in the shadow areas. The GH4 files displayed  negligible color shift.

With respect to digital luminance noise (grain) and ability to resolve detail I found no difference between the GH3 and GH4 at any ISO setting.

There was negligible chroma noise from either camera.

But several reviewershave reported that the GH4 provides a modest IQ improvement over the GH3.  How can this be ?

I think the  explanation lies with PsCR.  When I started using the GH3 I found that ISO 6400 files were quite grainy with magenta color shift in dark tones. Now with an updated version of PsCR the ISO 6400 files are less noisy and have negligible color shift.

I hypothesise that reviewers may have been comparing files from the GH3 converted with an older version of PsCR (and  saved as JPG or TIFF) with those from the GH4 converted with PsCR 8.6.  Or maybe some people just saw what they wanted to see.

The reasons for upgrading from a GH3 to a GH4 have to do with the EVF, AFC/Burst performance and 4K video.

The image quality/picture quality has not changed.