Panasonic G7 E-Shutter-vs-M-Shutter Image Quality

G7 ISO 6400 Mechanical Shutter (crop)

In their DPR  review of the G7, Richard Butler and Samuel Spencer point out that use of the mechanical shutter may be associated with loss of sharpness due to shutter vibrations. This is rectified by use of the Electronic Shutter as demonstrated in the DPR studio test scene.  

My own experience confirms this.

The authors say that ….images made with the E-Shutter….”come at some cost to  dynamic range and a slight increase in noise at the highest ISO settings”. 

Panasonic M43 cameras including the G7 record images using the M-Shutter at 12 bits per pixel.

But when using the  E-Shutter  some models record at 10 bits per pixel, presumably in order to speed up the E-Shutter scanning process. When it first appeared on M43 cameras, E-Shutter scanned the frame at about 1/10 second. The G7 scans at about 1/25 second but the penalty for the increased speed is reduced bit depth.

By the way I have seen early reports that the GX8  E-Shutter also scans at about 1/25 second but with no adverse effect on dark tone noise, suggesting full 12 bit recording even with the E-Shutter. I have not seen this confirmed as yet.

Update 28 September:  My tests show that the GX8  E-Shutter scans at 1/20 second with no impairment of image quality, indicating 12 bit capture.

Back to the G7, I wanted to know what effect the 10 bit E-Shutter capture would have on my photographs.

So I ran some tests with my copy of the G7.

G7 ISO 6400 Electronic shutter (crop)

The first test was to photograph a still life at ISO 6400, 12800 and 25600 using first the M-Shutter then the E-Shutter.

I then ran the images through Adobe Camera Raw (ACR) 9.1.1 at default settings and viewed the files at 100% on screen.

I could see no difference between the M-Shutter and E-Shutter versions at ISO 6400 and 12800.

At ISO 25600 the E-Shutter version showed a just barely detectable increase in grain and just barely detectable decrease in dark tone detail, but I had to pixel peep at 100% with the images side by side to see any difference at all.

The photos show a crop of the original full frame.

G7 Electronic Shutter ISO 200 Underexposed 5 stops, exposure increased 5 stops in Camera Raw

G7 Mechanical shutter ISO 200 underexposed 5 stops, exposure increased 5 stops in Camera Raw

Next I did a RAW torture test. This involved underexposing the same still life 5 stops at ISO 200 then in ACR pulling the [Exposure] slider 5 stops to the right.  This gave the same exposure in terms of aperture and shutter speed as an ISO setting of 6400.

When the M-Shutter was used this produced a normal looking photographic result, but a bit noisy and with some evident green color cast in the dark tones.

The test did show that setting ISO 6400 gives a better result with less noise and more accurate color than ISO 200 underexposed 5 stops then pulled up 5 stops in ACR.

When the E-Shutter was used there was more luminance noise and much more prominent chroma noise with a strong green cast in mid and dark tones. I could not find a way to correct this in ACR.

So, what is the point of this apparently stupid exercise ?

Nobody deliberately underexposes a photo 5 stops just to increase the [Exposure] 5 stops in Camera Raw.

The point is that it warns us what is likely to happen when we are working with a file in Camera Raw and we start to pull up the dark tones with the [Exposure] and [Shadows] sliders.

A photo made with the E-Shutter will show green blotchy noise sooner and to a greater degree than one made with the M-Shutter.

Does this matter ?

For the great majority of photos probably not.

But if you have a photo which requires the dark tones to be pulled up a lot in Camera Raw then yes, it could make a visible difference to the final result.