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Canon EOS Crop Sensor for HD
APS-C sensor cameras including the 80D, 70D, 7D Mk. II, 7D, EOS M and Rebel models for HD video recording.


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Old January 29th, 2010, 08:30 PM   #1
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7D Moire/aliasing !

I shot some footage today with my 7D of some brick walls at a distance, and lo and behold...that nasty moire/aliasing pattern! It really is awfully obvious. I researched the heck out of this camera before I bought it a few days ago and this didn't come up as a paralyzing problem, but it really is a sore thumb in such an otherwise great piece of hardware.

So my questions are thus:
Why did I buy this camera?

Also,
Is it fixable? In other words, can I expect a firmware update to set things right, or is this wishful thinking? I understand the concept of how the sensor "downscales" from the sensor to 1920x1080 in the most lazy way possible--skipping lines, boo!--so can a rewrite of the firmware fix this, or is reasonably clean footage of horizontal patterns simply outside the capabilities of the camera?
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Old January 29th, 2010, 09:18 PM   #2
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You need better skill in the search, the moire and aliasing was well known and all over the net, the best solution is don't use it as wide infinite dof camera, but if you have to, what I do is I have the Zacuto so I can see aliasing crop up on buildings like that and I slightly out of focus it until the moire goes away and then add a little sharpening in post.
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Old January 29th, 2010, 09:27 PM   #3
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The best way to fix it is:
1) Put an actor a number of steps in front of the brick wall.
2) Set the lens to f/4 or wider.
3) Focus on the actor. (just make sure they're not wearing a finely patterned shirt.)

You can also take the edge off of aliasing with a diffusion filter, like a Soft/fx, pro-mist, or glimmerglass. There's no magic formula. It varies by lens and the look that you want. If you go too soft, you get the boudoir look. If you don't go soft enough, you won't see a difference.

These filters also reduce contrast. That makes it really hard to give a cookbook answer. If the contrast of your scene is already too low (say, on an overcast day), a diffusion filter can look terrible. On a sunny day, it might look great.
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Old January 29th, 2010, 09:45 PM   #4
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Quote:
Originally Posted by Ben Winter View Post
Why did I buy this camera?
Just go shoot some thin DOF in low light and you'll remember. ;)

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Also, Is it fixable?
Jon and Khoi Pham gave you good suggestions already. I can't think of anything else to add.

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In other words, can I expect a firmware update to set things right, or is this wishful thinking?
I don't know for certain, but I strongly suspect it's a hardware limitation.
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Old January 29th, 2010, 10:22 PM   #5
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You need better skill in the search, the moire and aliasing was well known and all over the net
I didn't say I didn't know about it, It was simply not emphasized to me as major nail in the coffin.

Canon 7d Tips Blog Archive Canon 7D Moire pattern test

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Most camera would have had some issues with all the overlapping vertical bars but the 7D handled it surprisingly well.
The focus fix came to me as I was playing around with it--it's still unfortunate, how can you not use a camera at full wide? I can deal with limitations, just frustrating to encounter one that could have been avoided (Canon I'm looking at you).
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Old January 29th, 2010, 10:32 PM   #6
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I didn't say I didn't know about it, It was simply not emphasized to me as major nail in the coffin.
Don't look at me. I emphasized the problem so much that people around here started giving me the stink eye. :)

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it's still unfortunate, how can you not use a camera at full wide?
That's what my XH-A1 is for. ;)

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Originally Posted by Ben Winter View Post
I can deal with limitations, just frustrating to encounter one that could have been avoided (Canon I'm looking at you).
Actually, I don't think it could have been avoided. I think their only choice was to give us flawed video or no video at all. I'm sure that eventually the hardware will catch up to the level we'd like, but for now we have to grin and bear it.

Last edited by Daniel Browning; January 30th, 2010 at 02:59 AM. Reason: Freudian slip
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Old January 30th, 2010, 02:11 AM   #7
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So my questions are thus:
Why did I buy this camera?
Because it only cost $1600. It's solid for the price. For the price.
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Old January 30th, 2010, 03:46 AM   #8
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I can deal with limitations, just frustrating to encounter one that could have been avoided.
I don't think it would make sense to say that it could have been avoided. There is some pretty complex number crunching involved in downscaling an image of 21,100,000 pixels to one of 2,073,600. On top of everything else that's going on in creating the 264 stream.

I'd rather say, Canon has revolutionized what many of us can do, and the inevitable improvements in tech over the next 2-3 years will knock our socks off.

From your site Bill it seems you make indie features. So you're up against Z1U's, XH's, HVX's and just maybe a few EX1's. I think you look pretty good shooting 7D.

Unless you're screening it on a giant screen with a super-critical and technical audience, I think you're good to go even with a bit of aliasing in certain shots. But it would make sense to follow the advice above to reduce it as much as you can.

Or, return the 7D, gather up about $10,000 on top of that, and get a Scarlet in ... months.
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Old January 30th, 2010, 06:44 PM   #9
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Ben,
Not to be a jerk but when you say you researched the heck out of this camera and didn't realize the extent of the issue, I have to wonder where you researched. The ailasing issue has been discussed ad infinum in many forums until it seems that is all that is talked about. This forum may be an exception, I don't know. Personally it hasn't been that big of an issue for me, I just try to avoid situations where it will pop up.
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Old January 31st, 2010, 01:34 AM   #10
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Ben,
Not to be a jerk but when you say you researched the heck out of this camera and didn't realize the extent of the issue, I have to wonder where you researched. The ailasing issue has been discussed ad infinum in many forums until it seems that is all that is talked about. This forum may be an exception, I don't know. Personally it hasn't been that big of an issue for me, I just try to avoid situations where it will pop up.
Clearly, issues are downplayed by a lot of people who are antagonistic towards second-guessing their $2k purchase. Perfection of an image is a priority to some, not to others. My mistake was not taking this into account.

The problem is incredibly disappointing to me. I may be an exception, I don't know.

Quote:
don't think it would make sense to say that it could have been avoided. There is some pretty complex number crunching involved in downscaling an image of 21,100,000 pixels to one of 2,073,600. On top of everything else that's going on in creating the 264 stream.
I'm in my last year of electrical engineering at UMD. They teach us that our major provides us the ability to take the complexity of real life and engineer solutions. I'm not going to pretend I'm familiar with the DSLR systems, but I am familiar with VLSI circuit design and DSP. This is a DSP problem: it is possible to engineer a solution. This was not an impasse, this was a decision to ignore the problem. As has been discussed on this forum and others, this is primarily a photographic camera. If the engineering emphasis had been on video the issue would have certainly been addressed. I have no illusions about the reasons behind the problem, I just feel a bit let down.
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Old January 31st, 2010, 01:57 AM   #11
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Avoiding Aliasing

I'm strongly considering buying a 7D. The only thing holding me back is the aliasing/moire issue. Whenever I see a horrible still-grab posted, I think about playing it safe with a more 'traditional' model, but then I remember all the amazing videos I've seen posted and wonder why it never affected any them. Can't take the back and forth much longer!

Is this a safe choice for someone whose only HD camera will be the 7D? What do I need to stay away from aliasing when using the 7D? What triggers it? Just a bunch of straight, parallel lines? I'd rather exclude all problematic objects/shots from the storyboards than have to correct for aliasing during shooting or in post.

Also, if I export to a lower res for displaying the video on the web (say 720 or 480) will this hide the aliasing or make it worse?
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Old January 31st, 2010, 04:03 AM   #12
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...downplayed by a lot of people who are antagonistic towards second-guessing their $2k purchase.
You make it sound like a lot of money. Not in this biz ;) Believe me, the 7D is a phenomenal steal. Unheard of bargain.

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Perfection of an image is a priority to some...
Name me a camera (any price) that produces a "perfect" image. Every camera has severe drawbacks, even the much-worshipped Red One.

Let me put it this way, I'd rather be a musician than an audiophile. Embrace the flaws and make art.
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Old January 31st, 2010, 04:14 AM   #13
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I'm strongly considering buying a 7D. The only thing holding me back is the aliasing/moire issue.

Is this a safe choice for someone whose only HD camera will be the 7D?
The 7D isn't an every down back. It's kind of like Reggie Bush. Used in the right situations, it's golden. If you want a one size fits all video camera, you need to spend over 15 grand. A cam with a seamless image, shallow DOF, low light ability, multiple frame rates doesn't exist below that mark.

And seriously, I can't imagine how anyone, at this point, could complain about being surprised that the 7d has moire issues. It's almost cliche to even talk about it.
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Old January 31st, 2010, 09:18 AM   #14
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Justin,
For 2K, nothing comes close. Not having to mess with DOF adapters, great low light, stealth design (video cam posing as a still cam) and interchangable lenses make this an absolute steal. The bad issues of moire, jello and crappy audio are disadvantages you need to consider before purchase, but remember ALL cameras have achilles heels and you need to weigh those cons against what you are planning to use it for. Ben apherantly didn't and is upset about his purchase, so think it out carefully and if your doing alot of run-n-gun shooting (jello) or shots of buildings, fences, tiled roofs, striped shirts, verticle blinds etc (ailasing) you will have issues :)
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Old February 10th, 2010, 08:11 PM   #15
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Here's a "real world" use of the 7D on a car lot with buildings, cars, trees, etc. - lines everywhere - and it held up real nice like me thinks. Client liked it for sure. :) Footage is shown here raw and then graded. Used "flat" setting shot at 1080p24...

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