The Dark Secret of Sony A7RIV

Well if you’ve paid enough attention to Sony’s latest flagship it’s not exactly a secret: the full pixel readout speed has dropped compared to A7RIII. And this leads to a series of unfortunate consequences.

When A7RIV was announced there were datasheets of two 60MP sensors on the internet leaked by the infamous 八妹 @E8M_HDR : one is IMX455 with 9.42FPS full pixel readout speed and the other is IMX551 with 12.62FPS. Many people including me thought that A7RIV was using the more advanced IMX551 because you simply cannot make a 10FPS camera with a 9.42FPS sensor. Well we were wrong. A7RIV is kind of a “fake” 10FPS camera. It’s using the so-called “chicken blood mode” that doubles the readout speed to 21.33FPS but sacrifices the image quality. You lose around 1.5EV dynamic range which is quite a lot.

The chicken blood mode is also implemented in A7RIII/A7III/XT3 and maybe some other cameras using Sony’s image sensors. On Sony A7RIII/A7III you have two ways to activate it:

1. Compressed RAW + continuous shooting
2. Video shooting (this is quite nice because you can reduce the rolling shutter by 50% now. With Sony’s pathetic 8bit 4:2:0 sub-sampling you can’t see any image quality difference anyway.

So far it’s the same as A7RIV. But there is a huge difference: A7RIII can still maintain around 9.3 FPS burst rate without the chicken blood mode. A7RIV can’t. If you use uncompressed RAW on A7RIV then the maximum burst speed is only around 7FPS. This is particularly bad for mirrorless cameras because the burst rate often determines the refresh rate of your viewfinder in continuous mode. 7FPS without liveview is basically in the Canon realm. It makes your eyes bleed.

If you turn on the compressed RAW and shoot 10FPS then the image quality will be significantly worse. So basically you’ll have to choose: either high dynamic range or high speed. You can’t have them all like A7RIII. But to be fair, even with the penalty from the chicken blood mode, the dynamic range is still quite similar to an EOS R…

So basically to get the most of your A7RIV you need to switch the compressed mode on and off all the time depends on what you are doing. I consider this extra step stupid and unacceptable.

BTW the IMX455 datasheet also shows that this camera is capable of 8K30P or 4K60P. Well, same Sony same story. The new crippling king after Canon?

The useless side stories: why is it called the chicken blood mode?

Back in the 80s most Chinese people still believed a lot of weird shits. The Chi Gong masters claimed that they can use their inner Chakra to cure diseases or put out forest fire thousand miles away or even stop a nuclear bomb. The Chinese government actually hired a telepathic firefighter called Yan Xin (严新) with tax payers’ money and he’s still a national certified Chi Gong master (or I’d rather call him X-Men) to date. The old cadres of the Chinese Communist Party also believe that they can keep themselves young and vigorous and probably perform better in the sack by injecting chicken blood into their bodies. So you get the idea, it’s basically the Chinese version of “on steroid”, but can also be a negative word depends on how you use it. For example if you think someone is easily triggered/acting too agitated like today’s social justice warriors you can call him “on chicken blood”.