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 Post subject: Flawed GH4 review
PostPosted: Thu May 15, 2014 6:27 pm 
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The GH4 burst mode depends on the lens attached to the camera. An Olympus lens will function slower due to not being currently supported by the Panasonic DFD technology - only Panasonic lenses are currently. How someone can perform a review of AF-C and tracking without trying it with a Panasonic lens like the 35-100mm, which does work at 7 FPS, is beyond me. What is worse is then to repeat over and over in the review the speed is only 5 FPS but never mention not trying it with a supported lens.
I would be good with mentioning not all lenses are supported as a "con", but implying no lens is faster than 5 FPS is very sloppy.

One other thing I noticed. The A6000 review tested with a 50mm lens at F/5.6 while the GH4 was with a 45mm lens at F/1.8 according to the review. Because of the very large difference in DoF, AF-C tracking really can't be compared.


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 Post subject: Re: Flawed GH4 review
PostPosted: Thu May 15, 2014 7:51 pm 
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Someone on another forum posted this.

Dual FAST AF is made possible by Contrast detection AF and On-chip Phase Detection AF. On-chip Phase Detection AF is used when a Four Thirds lens is attached, and both Contrast detection AF and On-chip Phase Detection AF are used when a Micro Four Thirds lens is attached for high-speed, high-precision autofocusing.

The GH4 review was wrong saying the E-M1 didn't use PDAF with micro four thirds lenses.


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 Post subject: Re: Flawed GH4 review
PostPosted: Sun May 18, 2014 11:57 am 
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Hi Randy, nice to meet you too! Thanks for coming along here and telling me I'm wrong in your very first posts - that's not a great start to a relationship is it? I spend five weeks testing a camera and writing around 20,000 words on it, then publishing it for free and all I get from you is 'Flawed GH4 review'. You're very welcome.

None-the-less, I'll address your comments.

I've spoken to Olympus many times about the PDAF system on the EM1, including engineers from Japan. My comments in my reviews are based on actual one-on-one press interviews with these people, not from repeating something I've heard from, or read on a forum elsewhere. So please don't tell me I'm wrong. I am merely quoting what I have been told in direct interviews with Olympus engineers. Have you spoken to many of them? I assume you must have to tell me I'm wrong. Who are your contacts there so that I can confirm what they've told you?

Now it's important to note these things aren't always black and white. In my 22 years of professional journalism I have often been told one thing by one person and a different thing from another. Sometimes companies can be deliberately vague about certain technical details, and at other times a spokesperson may not know but may say something to save face. As a journalist all I can do is base my reports on what the engineers tell me, and crucially what I observe in my own tests. The Olympus EM1 may in fact employ pixie dust for its AF for all we really know, but the bottom line is it's not exactly convincing when it comes to continuous AF using MFT lenses. I've tried it with the 45mm f1.8, 75mm f1.8, 12-50mm, 12-40mm, and a bunch of Lumix lenses and it failed to deliver - in my tests - a convincing ability to track moving action. Again your experience may vary. I can only tell you what I have personally found.

As for the GH4, I tried continuous AF with both Panasonic and Olympus lenses, for both stills and video, and I noted this in the review. I do know that the Olympus lenses are not profiled for Panasonic's new defocus technology, but as I noted in the review, I didn't notice a huge difference between them and the Lumix ones in my CAF tests. Indeed only very minor differences with the lenses I had available for testing.

As a one-man operation I do not have the entire MFT lens catalogue at my disposal, but I do have seven of my own lenses and I found with both Lumix and Olympus lenses that the burst speed when shooting with continuous AF and focus priority varied, but was generally between 5 and 6fps, as I quoted.

You seem horrified by this result, yet I actually consider it quite good for a camera with a contrast-based AF system. You may achieve slightly more with a certain lens I haven't tried yet, but it's not the performance you'll get from models like the A6000 and XT1. And while I'm still hoping to test the A6000 with other lenses, I have used the XT1 with the 56mm f1.2 at f1.2 and it can maintain the speeds I quoted.

Ultimately I do want to try the GH4 with other lenses to see if the CAF performance improves, but having tried it with two Lumix lenses and one Olympus for CAF tests, I stand behind what I've published.

Remember it's just an opinion based on my own tests and findings. Don't get your knickers in a twist over it.


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PostPosted: Sun May 25, 2014 1:10 am 
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I'm a fan of the GH4 and of the GH3 before it. While I don't totally agree with all the details, I think it is a fair (=honest) review. My reasons for preferring the GH4 over the E-M1 are ergonomics: My large hands prefer the GH3/4 and my mind has always been boggled by the Olympus menu system, so I sold the two Oly m4/3 cameras I owned. Somehow the Panasonic approach matches my mind better. And I think the review made the point that different users will have different preferences.

At ISOs below 3200 the GH3 images were fine in my view. And now the GH4 does better IMO than the GH3 did at 3200. So I'm pleased with the improvement.

I'm mainly a stills shooter, but now that I have a ground-breaking video capability I plan to get into that regime. I'm looking forward to it. Fortunately my preference in a stills camera made that possible. If I really like the E-M1 better I'd probably have gone that route and blown off the video features of the GH4.

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Phil Wheeler
Panasonic GH4; FZ200


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