Jim Kasson analyzed the Sony A7rIV files  and concluded:

I’m not going to bury the lead here: the Sony a7RIV eats stars just about like the a7RIII does…except that the new behavior starts at 3.2 seconds instead of 4 seconds.

Sony should really take  action and develop a special “star shooting” mode that deactivates the filtering.

On a positive note: Fixed pattern read noise is very clean. Jim Kasson writes:

These are very clean. I was afraid I’d see evidence of software designed to suppress PDAF striping.

Noise on long exposure is fine too:

It’s very clean except for the blue plane, ant it’s not bad at all.

Sony A7rIV and new accessories:
Sony A7rIV in USA/CA at BHphoto, Adorama, FocusCamera, Amazon, BuyDig, Henrys.
Sony A7rIV in EU at Calumet DE, ParkUK, WexUK, Calumet NL.
Sony A7rIV in Asia at Sony Japan. Sony Australia.
Sony VG-C4EM grip in USA at BHphoto, Adorama, Amazon, FocusCamera, BuyDig, ParkUK, WexUK.
ECM-B1M Digital Audio Shotgun Microphone at BHphoto, Adorama, Amazon, FocusCamera, BuyDig, Park UK.
XLR-K3M Mic at BHphoto, Adorama, Amazon, FocusCamera, BuyDig, Park UK.

Jordan Steele from Admiringlight tested the new lens and concludes:

Pros

• Extremely compact and lightweight lens
• Quick and accurate autofocus in most situations
• Very good image sharpness right from f/2.8
• Excellent color and contrast
• Outstanding flare performance
• Good control of both lateral and longitudinal chromatic aberration
• Excellent value

Cons

• Limited zoom range
• Bokeh is a bit rough and high contrast
• Relies on software correction for distortion and vignetting
• Autofocus can miss in continuous AF on distant subjects

The Tamron 17-28mm f/2.8 keeps with Tamron’s full-frame mirrorless philosophy so far.  It sacrifices a bit of zoom range for compact size while keeping the optics on a high level and the lens affordable.  The 17-28mm packs a constant f/2.8 aperture into an ultra-wide lens that is smaller and lighter than Sony’s slower 16-35mm f/4, while being significantly smaller than the 16-35mm f/2.8.  Despite the small size, the lens performs very well.  It’s sharper than the 16-35mm f/4, and produces images with great clarity, good sharpness to the corners and fantastic flare performance, making it a great option for landscape photographers who want to travel light.

While the f/2.8 aperture will enable lower light usage and can provide some subject isolation, the bokeh is only average at best.  However, given the cost of this lens, at just $899, Tamron’s tradeoffs here are more than worth it.   While many will compare this lens with the 16-35mm f/2.8 GM, I think that those who are willing to shell out the astronomical $2300 for that lens will not be swayed by third-party glass.  But where Tamron will certainly succeed is in competing with the slower Sony/Zeiss 16-35mm f/4.  In this comparison, the Tamron is not only the better optic, but adds an extra stop of light while saving the buyer $400. It’s a great addition to the full-frame E-mount.  I have sold my personal Sony 16-35mm f/4 in favor of this new Tamron.  I suspect many others will do the same.

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Tamron 17-28mm f/2.8 FE:
In the USA at BHphoto, Amazon, FocusCamera, BuyDig and Adorama.
In Europe it’s available at Amazon DE, Calumet DE, WexUK, Park UK, Amazon IT, Amazon FR, Amazon ES, CameraTools NL.