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 p.3 #1 · When is the new Sony A7C III coming out? | |
chiron wrote:
Yes, but at the cost of dynamic range, resolution (in the case of the A7CR), and, most importantly, at the cost of a very significant difference in size and weight. The A9III is a great camera for the right user, but it is not an A7Rxx.
Having shot with the A1, A9 III, and various A7R bodies, I have a few thoughts.
Yes the A9iii is not an A7Rxx, but the weight difference is not as much as you make it out to be. In fact the A7RVI is somewhat heavier than the A9iii!
Dynamic range
The A9 III's dynamic range disadvantage is most pronounced at ISO 100, simply because it doesn't offer a native ISO 100 setting. At higher ISOs, the gap narrows considerably. In my experience, at ISO 250 and again at ISO 800 and above (the A9 III's second base ISO), I see little practical difference in dynamic range between the A9 III and A1. Ultimately, how much this matters depends on what you're shooting.
Resolution
The same applies to resolution. In my testing with the 70–200mm GM II, the difference in resolved detail was roughly equivalent to a 10% change in focal length. In other words, an A1 shot at 70mm, f/2.8 produced comparable detail to an A9 III shot at approximately 77mm, f/2.8.
This comparison was conducted at base ISO, and I would expect the gap to narrow further at higher ISOs as noise becomes a greater limiting factor.
Of course, lens performance also plays a role. With a GM prime stopped down to around f/2.8–f/4, where sharpness is typically near its peak, I would expect the resolution advantage of the A1 to become more apparent than in my zoom lens test. But that assumes there's enough light on the subject to stop down while remaining at the first base ISO.
If ISO has to be increased to achieve optimal lens sharpness, some of that sharpness is destroyed by the increased noise so it may be ultimately counter productive
Flash photography
Ironically, in real-world photography, the A9 III may actually have an advantage by allowing you to shoot at more favorable apertures.
Thanks to its global shutter, the A9 III can synchronize a speedlight at very high shutter speeds without the enormous loss of effective flash output associated with HSS. With the F46RMA, the advantage is about 4.5 stops, making the same speedlight substantially more effective on the A9 III.
To put that into perspective, 4.5 stops represents roughly 23 times the effective flash output. In terms of energy, that's the difference between 75 Ws and approximately 1,700 Ws.
For example, if f/2.8 is the sharpest aperture on my prime, I can shoot at f/2.8 on the A9 III and use a fast shutter speed to control ambient exposure.
On an A7R body, the same speedlight simply doesn't have enough power to achieve this in HSS. The alternative is to stop down to f/11–f/16 to stay within the normal flash sync speed, but even then, the speedlight does not have enough power to overpower the sun. As a result, the subject ends up underexposed, requiring the exposure to be raised in post-processing, which increases noise and destroys detail.
In fact, by stopping down to f/11 the A7RVI will only produce about 16MP worth of detail because of diffraction! https://starlight-code.com/posts/diffraction-calculator/
So while the higher-resolution body has a theoretical advantage in resolving detail, the A9 III's global shutter can sometimes allow it to operate closer to a lens's optimal aperture which yields more resolution under actual shooting conditions.
Ultimately, the right camera depends on the subject, available light, and how you're shooting.
For example, my 600ws AD600 weighs 3.5kg. In situations where I can use as many strobes as I want then yes the R series body will be the right camera to pick for that shoot!
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