GH1, meet the DSC MegaTrumpets res chart

[Barry_Green]

I have my GH1 back, and am now able to start duplicating some of the tests the 7D got put through.

First up, is the DSC Labs MegaTrumpets 12 res chart. For those who didn't follow the other thread, basically the MegaTrumpets 12 is designed to handle up to 4K cameras like the Red One or Dalsa Origin. My older res chart topped out at 700 lines, not nearly enough to show what these cameras can do, so I got the MegaTrumpets 12. It's great because its highly precise and it shows resolution trumpets not just on the horizontal and vertical, but also at many different angles.

As expected, there are mixed results, and the overall results show the same basic kinds of patterns that the 7D exhibited. Here's the chart, side by side with an extraction of the 7D's chart:





I've gone through and marked some areas of special interest on the chart. At first glance, the GH1's chart looks a lot better than the 7D's, because the GH1 doesn't have the bizarre color mush that the 7D exhibits. However, other than that particular anomoly, they're fairly comparable.

In spot "A", the Canon looks like it's actually rendering cleaner than the Panasonic. There's not much horizontal resolution here, about 700 lines on the Canon, and maybe 600 on the Panasonic before the aliasing renders it moot to look further.

In spot "B", that's where the Canon just pukes in an alarming fashion, turning a pure black & white chart into a mishmash of purple and green. The Panasonic does much better. The Canon doesn't even resolve 500 lines cleanly, it's already heavily aliased even at the start, whereas the Panasonic gets to probably 550 before the aliases blur the res completely. As far as detail extinguish, the Canon gives up at about 850 lines, whereas the GH1 is still rendering aliased detail until about 1100. This is not actually good, it'd be good if there was clean rendering until 1100 lines! The actual and legitimate detail is higher on the GH1 than the 7D vertically, and higher on the 7D than the GH1 horizontally, by probably about the same margin. Based on that, I predict both cameras will deliver images that are about the same actual sharpness. The color patterns are disturbing on the Canon however; I suspect it will cause problems on greenscreening that the GH1 wouldn't have.

In spot "C" there's some interesting things happening. On the Panasonic side there's a tiny bit of purple color contamination, never a good thing. Nothing compared to the Canon's color contamination in "B" or "D", but still, it's there and it shouldn't be. Look at the pattern of lines on the Canon side in "C" -- they're actually sweeping fully horizontally! Once you see the pattern on the Canon, look at the Panasonic side and you can see that it's doing it too. That's bizarre, and that's why aliasing is so bad. It makes you think you're seeing something, but it really isn't there! The charts consist of straight lines from the outside to the inside, straight nearly-parallel lines that converge at the center of the chart. So it looks like the Canon and Panasonic are rendering sideways lines, but it's supposed to be perfectly straight lines! What looks like detail here is "false detail", it's contamination in the picture. A lot of the perceived sharpness in the GH1 and 7D and 5D can be directly attributed to this kind of false detail.

I mean, let's look at the HMC40's trumpet so you can see what a trumpet is supposed to look like:


That's what it's supposed to look like. Clean line separation until the lines blur together into mush. And once they blur together, they should stay together. All the wedges should look like this. The way the 7D and GH1 are performing, there's all sorts of false detail being rendered. That false detail is a just plain wrong representation of the picture!

Okay, moving on, to "D" you can see the Canon again exhibiting some bizarre aliasing and color mushing. Keep in mind that there should be 15 thin black & white line pairs in this image, and only 15 thin black & white line pairs. Where did it come up with four purple & green lines? This is not image detail, this is contamination.

On "E" you can see a reasonably well-behaved trumpet from the GH1. Clean detail, little aliasing, nice and cleanly rendered down to detail extinguishing at about 900 lines. But -- then what happens? We get a return of some bogus false detail afterwards... sigh.

On "F" you can see really bad examples of this bogus false detail. After the image has completely exceeded the sensor's ability to render it (the complete detail extinguish point), then some "detail" returns, and we see more lines. These lines are fake. They are wrong. There should be 15 lines there, not four. And they should converge inwards, not outwards. These fake alias lines are bending away from the converge point, not towards it. The GH1 does it too, just not as bad. This is pollution in the image. It can actually make the image look sharper, but it's cheating, an ideal camera design would filter all that stuff out.

Net conclusions? The GH1 and the 7D (and the 5D) don't display true high-def images. The GH1 and 7D look like they probably have about the same amount of real detail in 1080p mode, which would be the amount of detail you could expect from a 720p camera. They do, however, render a much sharper-looking image because of all the false detail they let through. Even though their overall true detail might be comparable, the GH1 is clearly much better behaved on the charts, showing less aliasing and less bothersome color contamination.

Both cameras are capable of truly astonishing imagery. But both of them are resorting to smoke and mirrors to make it.



As for 720p, it's no contest -- while they both have aliasing, the GH1's chart just looks much better. Substantially higher res in the vertical; the 7D is well into the green/purple mush where the chart even begins, whereas the GH1 looks to be clean to 550 lines or more. The 7D's horizontal resolution is strangely well behaved, compared to all the other trumpets... odd.

[commanderspike]

Can coloured moire be removed in Final Cut Pro by ways of a plug-in or filter, or at the transcoding stage / in Voltaic?

[cowpunk52]

I really appreciate these tests, Barry. Thanks for doing it, and thanks for posting it - we all have a much better understanding and appreciation for the strengths and weaknesses of these cameras now.

[Ben_B]

In 1080p the blacks on the GH1 look better and the edges look sharper.

[Ozpeter]

Exactly how were these images taken in the first place, Barry? Was any kind of post-pro conversion involved? Are they freezes from running footage? Sorry if you've previously explained that but I didn't see any previous discussion.

[Ozpeter]

But both of them are resorting to smoke and mirrors to make it.

The 7D resorts to smoke and mirrors, but the GH1 has no mirror so it's smoke only. ;)

[commanderspike]

The 7D's horizontal resolution is strangely well behaved, compared to all the other trumpets... odd.

There is no doubt the GH1 does a better job of scaling the image.

Why do you think the 7D's 720p is so well behaved horizontally and not vertically. Could that be to do with line skipping, or binning pixels in groups of six and if so which method would cause it to behave badly vertically but better horizontally?

[J Davis]

If Panasonic are clever they will start shipping non japanese body only versions sometime soon.
At their price point and with results like these charts it would combat canon sales well.

[Barry_Green]

In 1080p the blacks on the GH1 look better and the edges look sharper.

You shouldn't be making judgements of that nature, as the chances the sharpening was set to identical levels is probably pretty low. IIRC, the GH1 shot this in "standard" mode, with sharpening at default, and so did the 7D (sharpening at 3). But the 7D's midpoint doesn't necessarily mean the same amount of sharpening as the GH1's midpoint...

[Barry_Green]

Exactly how were these images taken in the first place, Barry?

Pointed the camera at the chart and shot in movie mode, then extracted a still in post.

Was any kind of post-pro conversion involved?

No scaling or stretching. I may have used photoshop's "auto tone" to equalize out the whites. But no conversion to cineform or anything, these are direct frame exports from the native h.264 files.