I don't think there's much wrong with the slower sensor to be honest, I have come round to it, and I really like the FX2 as well - the images speak for themselves and it's one of the only cheap cinema cameras with both a proper EVF and mechanical shutter, and we all know that hybrid is where it's at... And again worth saying that unlike Panasonic S1 II - it is in the body of the flagship pro camera, not in the cut-price shell of a mid-range consumer camera.
The partially stacked sensors are of course the current cutting edge, a7 V will be great but only if you NEED the speed. I don't shoot much 4K120p or 60p. Cinema 24p is still my most valued spec in terms of frame rates and as for 30p, it is still a TV / YouTube frame rate and doesn't look cinematic.
Getting all this sensor talk in perspective, we'll go back to the very start.
Canon used a Panasonic CCD in their first 1D DSLR, their own pioneering CMOS tech was not yet ready in time so they switched plans. Then, from the first Canon 1DS it was ready to go - BUT CMOS at this time was much slower than CCD. The 1D classic is the only FAST pro sports cameras ever made with a CCD!
In the following years Canon were able to go from behind with CMOS and take the speed crown away from CCD sensors. The in-line A/D line-by-line readout tech of CMOS is what enabled video. Sony in 2005 commercialised their first CMOS sensor in the Sony R1 APS-C bridge camera. It had video only in terms of it could do live-view. The 10MP raw photos still stand up today. The way CMOS handles dynamic range is also different to CCD - a linear sudden blow-out in the highlights, but on CCD a more film-like non-linear and gradual highlight roll off and it was not until the Sony a7r III in 2018 that CMOS started to match CCD for colour fidelity and latitude.
That is 18 years of development progress.
The a7 IV sensor is a faster version of one of that chip, one of the most groundbreaking sensors of the last 25 years. 33mp instead of 42mp, but it sped up to enable a 7K full width pixel readout rather than pixel binned 4K.
In 2025 it's still one of the only mid-range cameras to go past the 24mp mark.
I think for £1500 that is a decent offer?
Have you seen the a7r III's images? It's absolutely stunning, in some ways beats an a1 and z8.
The a7 IV's "slow sensor" is at that level.
From those very early days in early 2000s, video took another 8 years following the debut of CMOS - first with the Nikon D90 and then with the 5D Mark II. It took a further 6 years until 2014 for anyone to make a 4K capable full frame CMOS sensor. The a7r II was the first to do oversampled 5K->4K in S35 mode and full frame pixel binned 4K. Oooooodles of stuff has been shot since on this camera and on many other cameras with a similar level of rolling shutter. Of all the specs I care about, rolling shutter only occasionally presented itself as problem in the real world.
I've owned countless full frame cameras... Panasonic S1, S1R, S1H, Sony a7s III, Sony a1, Nikon Z9 and Z8 but sold all of them. The only mainstay for me is the GFX 100. The only thing the faster Sony and Nikon cameras offer to the creative process, is speed and less rolling shutter. If action sports and slow-motion is your bag then great.
When the a9 III with global shutter (and the slightly noisy base ISOs) comes down to under £2500 I might consider one of those but until then...For cinema... I think the a7 IV and FX2 are the best images you can get for the price.
Although the Panasonic S1H has the edge in low light, and for HDMI RAW output to a hateful Ninja, it lacks the autofocus, the ecosystem of E-mount, and also of course the small and light body size.