Some preliminary comparisons between the GH5 & A7iii
I thought this might have some use for those debating between these 2 cameras. Obviously these are just my opinions:
EVF & LCD viewfinder- The GH5 has a higher resolution EVF. That's useful in some instances when punching in MF, but for my purposes the A7iii's OLED EVF was fine and up to the task. The one thing I didn't see in reviews, that I noticed immediately upon using the A7iii, was the Sony's EVF is significantly brighter than the GH5's EVF. I found that actually more than compensated for the loss in resolution. The other good news for LCD users (I use the EVF almost exclusively), is the dimming when shooting 4K is gone. The screen remains very bright.
IBIS- This was a major concern for me initially. My previous experience with Sonys, right up to my A7Rii and a brief time with the A6500, was the IBIS was not great and significantly worse than the GH5. The A7iii's IBIS is the best I've experienced in a Sony and surprising given it's FF camera. Is it as good as the GH5's IBIS? Nope. However I've found it's good enough so as not to be distracting, even when shooting at longer focal lengths. Many of the shots I took with the A7iii at the Bronx Zoo were at furthest reach of my 18-200 Sony lens. With even just a bit of bracing from something like a post, tree or fence, the stability was actually quite good.
AF- Without question, this, IMO, is the killer feature of the A7iii. Is it better than the GH5's AF? Not even close. With virtually every other mirrorless camera I've used, both Sonys & Panasonics, I would tend to use AF lock. Even with my A7Rii, AF lock was used more often than not. With the GH5, it's almost a necessity. Now to be fair, for most of the shooting I do, I can get away with AF lock. However if the dynamics of the scene and the movement of the subject is toward or away from the camera, AF lock is a non-starter. When I shot with CAF at Universal with the GH5, during the nighttime Mardi Gras parade, I got hurt with the CAF. What makes the performance of the A7iii's AF particularly impressive, is that being a FF camera, the DOF can be shallow, creating an even greater demand on AF accuracy.
Every shot I took at the Bronx Zoo was in CAF, never once did I use AF lock. Of the 65 shots I took there, 63 were perfect. One shot was very tough in that there were heavily detailed rocks about 6' in back of the monkeys I was shooting. There were times the monkeys stood up in front of the rocks and other times they ducked down. During that time the camera briefly focused on the rock behind rather than the monkey. I didn't try using tracking AF which might have solved that issue. However the success rate and the difficult of some of the shots I took, left me much more than satisfied. It was an AF freedom I haven't experienced since using a Canon camcorder. It's something I've never experienced in a mirrorless camera.
Low light- For many, this too will be a killer feature of the A7iii. The camera pretty much sees in the dark. Do I personally need this level of low light performance? No, but at ISOs I would shoot at, the lower noise levels help. Again, this is a big advantage over the GH5, whose low light performance I never thought was particularly bad. I think for some users this could be a huge advantage. It should be noted that at high ISOs, there is a softening of detail in the Sony. Panasonic is much less aggressive with this than Sony. However the GH5 can't get close to the high ISOs that the Sony can.
Detail & Resolution- The A7iii does present a somewhat more detailed picture than the GH5, but I really only noticed this when standing closer to my 77" screen than I would normally. At typical viewing distances, this mostly disappeared. Thus, although the advantage does go to the A7iii, I think many will never notice it and it's something I didn't get too excited about.
Color- Ah color. I first noticed a change in Sony's 'color science' (a phrase I hate) with my brief stint with the A6500. The A7iii similarly shows this improvement. However with that said, out of the box, I still prefer the Panasonic GH5's color. As I always do, I'm fine tuning the Sony's color to mimic the GH5 as best I can. Of course this is entirely subjective and some may prefer the A7iii's color over the GH5. Fortunately the Sony gives you a myriad of adjustments to fine tune that color. I'm working within the PP10 picture profile (HLG).
HLG- These days I'm shooting virtually everything in HLG. The performance is simply too good not to IMO. Unlike the GH5, the Sony has no option for 10bit, so 8bit it is. Without getting back in to some of the previous arguments we had in another thread, I find the differences between 8bit and 10bit to be so small, as to be simply 'unobservable' at typical seating distances. I said that before and I'll say it here, the Sony doesn't change that picture.
Comparing the actual HLG quality of the GH5 to the A7iii, is interesting. My initial reaction was that the GH5 had a bit more 'punch' than the Sony. I have noticed, for many years, actually going back to the days of VHS, Panasonic always strives for a punchier picture than the competition. I saw this in their TVs, VCRs, cameras, you name it. They are apparently tailoring the gamma to present a picture with greater contrast, which most consumers like. I tend to like this look too, so initially I was a bit disappointed. However I found that by simply dropping the black level of the A7iii a bit (another available setting in the A7iii's PP), I could get the same level of punch as the A7iii at perhaps a slight loss of shadow detail that was also apparent in the GH5. However the Sony's picture was overall brighter than the GH5. I suspect the greater DR of the A7iii comes in to play here.
The one significant Sony disadvantage for some, is how you watch your HLG footage. Since the GH5 outputs a 10bit stream, most newer HLG-capable displays are happy and show the footage in wonderful HLG directly from the camera. The Sony however only outputs an 8bit stream. Most HLG displays are not happy with that, although I think that some newer Sony TVs can show 8bit HLG directly from the camera. However my older and newer LG OLEDs would not show HLG directly from the camera, nor would my Sony UHD TV that's about 3 years old.
So how does one watch this 8bit HLG footage? You need a device that accepts the 8bit output from the Sony and outputs a 10bit stream to the display. In my case I use the Oppo 203 4K BluRay player. Most people with UHD TVs will want a BluRay player anyway, so it makes sense to get something like the Oppo that can handle HLG. The Oppo has 2 USB inputs, so I have one dedicated to a card reader and the other to a USB drive. It's easy to remove the SD card from the camera and insert it into the card reader. I can then review all my footage in HLG. Likewise, I can take an edited project and throw it on to a USB drive and watch it in HLG via the Oppo. I'm not sure what other 4K BluRay players have this capability. I'm sure it will become more common as time goes on.
60p vs 30p- I think I once said I'd never buy another camera that didn't have 4K60p. Oh well. Would I have liked Sony to have finally awakened to 4K60p? You betcha! So I've gone back to using a 'smooth' motion setting on my TV when viewing the 30p footage. This is essentially a frame doubler, but a bit more sophisticated than that. It does go a long way to making 30p look like 60p, but depending on the scene, it's still not 100%. This is the setting that when used with film, makes film look like video, the dreaded SOE (soap opera effect). Obviously for video effect this has no significance.
Overall I'm very pleased with the A7iii and think in some important ways it represents an improvement over my GH5. There are some aspects of the GH5 that are still, IMO, superior. One has to look at how they shoot and what's important to them to determine which camera present the best solution. As we always say here, there is no perfect camera and the A7iii does nothing to change that, although some may feel it gets us closer.
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