Update on Sony A7R IV Lens Mount / Sensor Parallelism, Lens Skew of Sony FE 12-24mm f/2.8 GM, Coming Field Shooting
My gratitude to B&H Photo for getting me a brand-new Sony A7R IV (currently the best mirrorless deal on the market at $2998, see below). Please give B&H Photo your business using any link or add on this site, or things like wishlists. Curiously, the Sony A7R IV arrived with firmware v1.00, so I updated it to v1.20.
Previous testing with my A7R IV (in for repair) showed nearly identical behavior with both samples of the Sony FE 12-24mm f/2.8 GM, as well as the same behavior (focus skew further in the distance) with the Zeiss Loxia 21mm f/2.8, Sigma FE 14-24mm DG DN Art, and Sony FE 12-24mm f/4G. Which is what made me suspicious of my A7R IV.
Promising results with independent confirmation
Last night I made a preliminary determination with the new A7R IV and one sample of the Sony FE 12-24mm f/2.8 GM that the new camera is notably better. However, there is still a left/right focusing distance skew and what I would call a “roll” to the sharpness (left/right and something else going on which could be tilt in addition to swing). Whether this is the camera or the lens is difficult to determine, but when I get my repaired A7R IV, some insight might be easier.
I came to this conclusion with several series, then sent images of the best scene to two other insanely picky photographers who spent years (literally) picking apart these issues of lens mount / sensor parallelism and lens skew and optical decentering in the quest for a perfect astrophotography camera+lens. Their empirical knowledge to be as good as it gets.
These experts confirm what I’m seeing, albeit being generally happy with what is still obviously “off” somewhat, their satisfaction being based on their disappointing past experience with 9 or so Sigma 14-24/2.8A lens samples and various other lenses.
In other words, the Sony A7R IV and Sony FE 12-24mm f/2.8 GM that I have now might be about as good as you can expect without trying a very large number of samples of both. Such is the state of tolerances for both lenses and cameras. Surely there are better cameras or lenses that exist, but it’s not like I can get a cherry picked lens or camera on short notice.
I will be leaving within two days for shooting in some glorious clean air (if it stays that way*) in the White Mountains and Eastern Sierra. Sony should be able to ship me my repaired camera over there to a friend about a week from now, so I can compare cameras with the same lens(es).
UPDATE Oct 18: hazardous air quality has moved back into the Eastern Sierra (AQI of 200-350 over a long section). The White Mountains have been oscillating between super-clean and very bad daily, so that area looks sketchy also. I don’t have sufficient A/C power to run my HEPA air filter in my van if I park for more than two days without driving, so I am holding off to see if air patterns shift.
I am keen to own a 12-24mm f/2.8 zoom that can persuade me of its equality or superiority to other zooms and prime lenses in its range—even if I have to work a little harder to deal with its foibles. This is what I plan on exploring:
- Absolute performance across the 12-24mm range of the Sony 12-24/2.8GM—what can you realistically expect from f/2.8 through f/11.
- Relative performance versus primes (Zeiss 18mm, 21mm, 25mm) and against other zooms like the Sigma FE 14-24/2.8 DG DN Art.
- Best practices to reliably get the best total sharpness from the Sony 12-24/2.8GM (and Sigma 14-24/2.8 which behaves similarly)—given less then perfect symmetry and pronounced focus shift, how do you place focus within the frame, at what distance, and how to focus exactly.
The gating factor for me is an oscillating energy (EBV and Hashimoto’s Thyroiditis) which can leave me extremely weak and unproductive. Home has been very stressful due to constant heavy construction equipment next door with noise and fumes and dust (more than a year now!), so I am hoping that the tranquility of the mountains will help me gain strength (I could not leave for ~10 weeks due to the smoke and fire issues but now I can). But the pace of my work may come in bursts due to this challenge as I may be forced to mostly rest at times.
* Still a week away, as Sony is replacing the A7R IV sensor/shutter assembly and the main circuit board before re-evaluating it.