In-depth Fujifilm GFX 100II Sensory Analysis – ISO 80 is Smoke and Mirrors, Electronic Shutter Hasn’t Changed, and More

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Jim Kasson from the Last Word blog has done some in-depth analysis of the Fujifilm GFX 100II and it looks like the Fujifilm GFX100II is more of a technologically tweaked GFX100 than a camera that should be called the GFX100II. I have been following Jim’s disappointing findings for weeks now, but he is only starting to reach conclusions about the sensor inside of the new GFX100II.

I personally feel like the Fujifiilm GFX100II is a cash grab released to temporarily increase GFX sales until Sony develops a true next-generation medium format sensor. Don’t get me wrong no camera competes with the Fujifilm GFX100 yet, but there is a perception that newer is better and unless your work depends on fast AF speed there is no reason to upgrade to the GFX100II.

If you are a budget-minded photographer now might be a great time to pick up a GFX100 or GFX100S used before more people realize that the camera can still compete with the Fujfiljm GFX100II. Especially since they are on sale.

The Last Word – Fujifilm GFX 100 II EDR, read noise spectrum

Well, that’s interesting! Fuji is applying a lowpass filter to that plane at ISO 80 that’s much stronger than the weak lowpass filter it’s using at ISO 100.

I call that cheating.

The Last Word – Fujifilm GFX 100 II EDR, spectra, 16-bit precision

The earlier camera is somewhat better from ISO 100 to ISO 400, at which point the differences become academic. However, the GFX 100 II excels at ISO 80, with an increase over ISO 100 that I’m having a hard time understanding.

The Last Word – Fujifilm GFX 100 II EDR vs shutter speed

There is a green tinge to the right hand side of the image.

The Last Word – Fujifilm GFX 100 II: more on EDR vs shutter speed

In this image, the green-tinged regions are at the top and the bottom. This looks more like traditional amp glo, which is an effect where the heat generated by the programmable gain amplifiers and analog to digital converters at the the top and bottom edges of the sensor adversely affects the accuracy of the readout. That effect occurs with the GFX 50 megapixel sensors, but it is usually in the bottom of the image only and the color tinge is magenta, not green.

I’m going to ignore this for a while and continue to test the camera. This looks like something that will mainly affect astrophotographers, and they often do black frame subtraction which should help a lot.

The Last Word – How fast is the GFX 100 II electronic shutter?

Now there are 42 bands. 8.33*42 = 350 ms, or about 1/3 of a second.

This is exactly the same as the GFX 100 and the GFX 100S.

Fuji has advertised the GFX 100 II as having a faster readout rate than the GFX 100S. From the looks of this test, that ain’t right.

The Last Word – More on GFX 100 II electronic shutter speeds

Similarly to ES, in CH mode, it looks to me that with MS the ADC is running in 12 bit precision, and that there’s some in-camera post processing that partially fills in the unpopulated buckets.

So there is a mode that yields faster readout rates than the GFX 100S, but you have to set the camera up right to get it, and it comes at a cost.

The Last Word – GFX 100 II read noise in CH drive mode

ES looks pretty much the same as MS.

The Last Word – GFX 100 II EDR, shutter speed in CL mode

Same as single shot mode.

The Last Word – GFX 100 II EDR summary

The ISOs above about 12400 are affected by the camera’s internally applied filtering, even though all such filtering was supposedly turned off in the menus.

Except at ISO 80, the GFX 100 II has somewhat lower EDR than the GFX 100S.

The Last Word – Fujifilm GFX 100 II ISO setting vs gain

It occurred to me that Fuji might be cutting the gain ratio from ISO 100 to ISO 80 by more than a third of a stop. So I made a series of images of the same scene (with no lens on the camera) at a fixed shutter speed and the ISO settings from 80 through 250. Then I looked at the ratio of the raw values in a crop of about 50% of the image area over the ISO setting. In theory, these should yield a constant.

The Last Word – Fujifilm GFX 100 II — a theory of the ISO 80 implementation

Fujifilm has stated that the GFX 100 II has a new sensor. But except for the ISO 80 availability and performance there, the GFX 100 II sensor looks a lot like the old sensor. Meet the new boss, same as the old boss? Maybe. Or maybe it’s that — echoes of Bill Clinton — it’s all a matter of what the definition of “sensor” is. I define the sensor as the silicon. Fujifilm may be defining it as that plus the color filter array, the microlenses, the hot mirror, and the rest of the sensor stack, and saying that if you change any one of those things it’s a new sensor. This is a bit like saying if you paint your white car red, it’s a new car.

The Last Word – Fujifilm GFX 100 II — preparing for photon transfer curve testing

I was concerned about the resolution of the display causing artificial fine detail. I dealt with that by defocusing the lens. I was also concerned that, at high shutter speeds, the persistence of the phosphors would not be long en0ough, making the refresh visible. A test shot at 1/4000 second with EFCS demonstrated that I don’t have to worry about that.

The Last Word – Fujifilm GFX 100 II EDR with and without LENR

When LENR is active, the camera makes a second exposure with the shutter closed, and subtracts that image from the first, normal, exposure. The purpose of this is to get rid of hot pixels that are the result of the camera’s integrating dark current over a long period. This ends up suppressing noise that is frame-to-frame invariant (like hot pixels), but, unfortunately, increasing the noise that is independent from frame to frame by about 40%. So you don’t want to invoke LENR unless you need it.

The Last Word – Fujifilm GFX 100 II — FWC, input referred RN, photon transfer curves

The camera is fairly ISOless from ISO 100 through ISO 400. There’s a big improvement in read noise at ISO 500 where the higher conversion gain kicks in. But there’s an anomaly similar to what we saw in the EDR curves. The read noise at ISO 80 iw way lower than I would think it should be. I still don’t have an explanation for that.

Read noise for the GFX 100 was a bit less than 4 electrons at the ISOs below where the camera changed to high conversion gain. That’s a bit better than we’re seeing with the new camera. That’s what the EDR curves showed, too. The read noise above ISO 500 is about the same for the two cameras.

The Last Word – Fujifilm GFX 100 II — ISO 80 and 100 shadow noise, visuals

The ISO 100 image is noisier. Not night and day nosier, but definitely noisier. This is a dark enough region that the read noise is significant (unlike the well-lit crops above), and the read noise reduction at ISO 80 compared to ISO 100 is visually apparent, and not just something that quantitative programs notice.

The Last Word – Fujifilm GFX 100 II — deep shadow noise at 14 and 16 bit precision

I could convince myself that the 16-bit crops are a bit smoother, but it’s not something that will affect real world image quality.

The Last Word – Fujifilm GFX 100 II — ISOlessness at low ISO settings

It’s clear that the ISO 500 images are the winners from the noise perspective. ISO 80 is no worse than ISO 400. I think you can treat the camera as ISOless over the range ISO 80-400 for almost all purposes.

The Last Word – Fujifilm GFX 100 II — ISOlessness at high ISO settings

The camera seems pretty ISOless in this range.

The Last Word – X2D, GFX 100 II base ISO visual shadow noise

The differences are underwhelming to me.

The Last Word – GFX 100 II, X2D — blur and distortion with IBIS and ES

By the way, if this little uncontrolled experiment is any indication, the GFX 100 II has better IBIS than the X2D.

The Last Word – Fujifilm GFX 100 II precision in CH shutter mode

+I’ve been asked how sure I am that the Fujifilm GFX 100 II uses 12-bit precision in CH mode.

Answer: pretty darned sure.

The Last Word – The reason for the GFX 100 II ISO 80 unusually good read noise

I could kick myself. The answer is obvious. At ISO 80 those folks at Fujifilm have dropped all the data below the nominal black point, slicing off the left half of the histogram, and cutting the measured read noise in half of what it would normally be. For shame, Fujifilm. For shame, Jim. I should have figured this out long ago.

The Last Word – In-camera black point subtraction

I’ve never seen a camera do what the GFX 100 II does, which is subtract (part of) the black point for one ISO setting, and not perform the subtraction for the other ISO settings. I struggle to imagine what was going through the Fujifilm engineers’ heads when they decided to do that.

The Last Word – GFX 100 II shadow noise at ISO 80, SS and CH

Well! It seems this camera has no end of tricks. It looks like the precision CH mode with ISO 80 is 13 bits. But maybe not. The lower part of the lowest pair of heavily-populated buckets is below the nominal black point, which is a little suspicious.

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