Day 4 field testing: notes on aliasing, camera support & meters at DVinfo.net

Go Back   DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon EOS Full Frame for HD

Canon EOS Full Frame for HD
All about using the Canon 1D X, 6D, 5D Mk. IV / Mk. III / Mk. II D-SLR for 4K and HD video recording.


Reply
 
Thread Tools Search this Thread
Old December 21st, 2008, 06:08 AM   #1
Major Player
 
Join Date: Jan 2005
Location: Wellington, New Zealand
Posts: 513
Some notes on aliasing, camera support & meters

Aliasing.... with the default settings, aliasing and moire patterns can be nasty (you don't need to hunt for artifacts, they pop out when complex geometric patterns or horizontal lines are in focus). However, after turning sharpness down a few notches, I didn't notice any problems at all with today's footage (shot in a variety of contexts). It would be interesting to learn how much perceived or actual resolution is being lost by decreasing sharpness, but from today's experience I'm going to keep it turned down.

Camera support.... today I shot using a monopod and lenses ranging from 24mm to 135mm. With my XH-A1, I frequently shoot with a monopod (or indeed handheld) to good effect, even at much longer focal lengths. With the 5d it's a different story. Anything over 50mm IMHO requires a tripod or steadycam as rolling shutter bites hard with even the slightest jerk. Having said that, rolling shutter is not an issue with smooth, controlled movements.

One caveat - I haven't tried an IS lens, which may improve the situation somewhat. But with primes, I won't be using a monopod beyond 35mm, or 50mm at a pinch. Also note (someone else mentioned this earlier and I can confirm), Smoothcam (the FCP filter) will not work with 5d footage as even minute rolling shutter causes havoc in the render.

So we have a very portable unit that demands very controlled movement.

Light meters.... I've never used a light meter, having always relied on my camcorder's internal exposure info. However, I've just ordered a Sekonic as I think it would be very difficult to expose correctly with the 5D without one. In order to set the camera to a desirable ISO, shutter speed and aperture, one has to perform any number of tricks (well documented elsewhere) to get the camera to behave. In the course of which, the camera ends up giving us exposure data out of context, unaware that there won't in fact be a torch in frame during the shot, or your hand covering the frame, or that you're about to stack ND's on the lens, or whatever. I am missing something, or do we all need light meters?

Last edited by Josh Dahlberg; December 21st, 2008 at 07:29 AM.
Josh Dahlberg is offline   Reply With Quote
Old December 21st, 2008, 06:55 AM   #2
Regular Crew
 
Join Date: Mar 2008
Location: Paris, France
Posts: 80
Do you have video frame captures with and without sharpness, showing the problem ?
Robin Lobel is offline   Reply With Quote
Old December 21st, 2008, 07:38 AM   #3
Major Player
 
Join Date: Jan 2005
Location: Wellington, New Zealand
Posts: 513
I'll try and get you something tomorrow. Jim Jannard posted a chart over on the Red user forum demonstrating the effect (I can't find it just now but there is a link to it on this forum). Of course, there's no issue with soft textures, natural environs, skin and the like, but when fine/horizontal lines enter focus it's not pretty, and the moire is much worse than anything I've previously encountered in video.

Don't let it put you off though. This camera has a lot more strong points than shortcomings - I'm really enjoying it so far.
Josh Dahlberg is offline   Reply With Quote
Old December 21st, 2008, 07:41 AM   #4
New Boot
 
Join Date: Nov 2008
Location: Key Largo, FL
Posts: 24
Great read. Thanks for the info.
Steve Mullholand is offline   Reply With Quote
Old December 21st, 2008, 08:35 AM   #5
Regular Crew
 
Join Date: Mar 2008
Location: Paris, France
Posts: 80
BTW, do we know how the cam perform the video scaledown ?
I mean, from the full sensor resolution down to 1920x1080, does it gently smooth using some bilinear/bicubic/.. filter, or a simple "nearest neighbor" method (which would explain the problems with thin horizontal/vertical lines).

I was a bit disappointed when I read Red was simply cropping into the sensor when shoting 2K.
Robin Lobel is offline   Reply With Quote
Old December 21st, 2008, 09:15 AM   #6
Major Player
 
Join Date: Mar 2006
Location: Chicago
Posts: 706
What's fairly clear is that alternating lines per frame are used when reading the sensor frame to frame. That seems to cause the problems with horizontal lines. In the future if they can read every line and downsample noise should be less. Since they apparently are reading every other line the downsampling algorithm is probably non standard. Add to that how they might build the different frame types and it gets very complicated.

One advantage of DOF control is allowing blurring of non critical elements. This caqn certainly help with both artifacts and perceived sharpness.

Beyond exposure control I'm not going to be working hard to get this camera to do things it doesn't do well.The testing being done here is very helpful in understanding the limitations of this model.

Considering even the sub $1000US single chip cameras now produce excellent images in good light, I'm thinking about the HF11 to shoot with the 5DII and go completely tapeless. I'm still unclear if AVCHP plays nicely with FCS, however.
Don Miller is offline   Reply With Quote
Old December 21st, 2008, 12:39 PM   #7
Major Player
 
Join Date: Feb 2006
Location: Philadelphia
Posts: 795
Quote:
Originally Posted by Josh Dahlberg View Post
In order to set the camera to a desirable ISO, shutter speed and aperture, one has to perform any number of tricks (well documented elsewhere) to get the camera to behave. In the course of which, the camera ends up giving us exposure data out of context, unaware that there won't in fact be a torch in frame during the shot, or your hand covering the frame, or that you're about to stack ND's on the lens, or whatever. I am missing something, or do we all need light meters?
Not sure how you would make use of a light meter with this camera in video mode - at best with nikon lenses you can get manual aperture control but you are still leaving shutter and iso up to the camera. You might be able to use the light meter to guess at what shutter speed the camera is going to use given a particular aperture, but even that would require a known ISO which I don't think is possible.

Even if we had full manual control I don't know that there's much use of a light meter in terms of setting camera exposure for video - I mean you can see exactly what you're getting on the monitor. The only thing I'd use one for is checking ratios for lighting - although even then final decisions are probably going to be made based on what the camera sees.
__________________
My latest short documentary: "Four Pauls: Bring the Hat Back!"
Evan Donn is offline   Reply With Quote
Old December 21st, 2008, 02:39 PM   #8
Major Player
 
Join Date: Jan 2005
Location: Wellington, New Zealand
Posts: 513
Quote:
Originally Posted by Evan Donn View Post
...at best with nikon lenses you can get manual aperture control but you are still leaving shutter and iso up to the camera.
Once you have aperture control, it's not too difficult to trick the camera into using the ISO and shutter speeds you want (it's just a bit fiddly, and then, there's always the issue of whether one can trust the exposure information provided).

Quote:
Originally Posted by Evan Donn View Post
"Even if we had full manual control I don't know that there's much use of a light meter in terms of setting camera exposure for video - I mean you can see exactly what you're getting on the monitor.
That's actually my reasoning behind using a light meter: the camera exposes as it sees fit > the exposure may be balanced, but it's not at a desirable shutter/iso/aperture > so we add/remove light by varying degrees to alter and lock down these parameters. Then, when one frames to shoot (the actual scene having less/more light than was exposed for), the LCD shows us the under/overexposure. I figure by using a light meter we would have a better target combination to work towards for a given shot, rather than taking a stab at it. Then again, one could always aim to slightly overexpose, then use the LCD as a reference for slotting in more layers of ND until exposure is correct.
Josh Dahlberg is offline   Reply With Quote
Old December 21st, 2008, 02:48 PM   #9
Major Player
 
Join Date: Jan 2005
Location: Wellington, New Zealand
Posts: 513
Quote:
Originally Posted by Don Miller View Post
One advantage of DOF control is allowing blurring of non critical elements. This can certainly help with both artifacts and perceived sharpness.
This is a very good point. While the aliasing/moire can be nasty, in a typical shot it's fairly easy to keep troublesome elements out of play controlling DOF. When problems do occur, they show up clearly in the viewfinder and you can deal with it on the spot. It's just something to be aware of.
Josh Dahlberg is offline   Reply With Quote
Old December 21st, 2008, 06:59 PM   #10
Major Player
 
Join Date: Mar 2006
Location: Chicago
Posts: 706
The camera is a light meter before we start messing with the video processes. Using manual exposure in photo mode the target exposure values for the scene can be determined. That's all a separate light meter is going to do anyways.
For people who have shoot film, it a normal process to decide how to get to the exposure value needed. It doesn't take too long to do this easily.
Don Miller is offline   Reply With Quote
Old December 21st, 2008, 07:44 PM   #11
Major Player
 
Join Date: Jan 2005
Location: Wellington, New Zealand
Posts: 513
Quote:
Originally Posted by Don Miller View Post
Using manual exposure in photo mode the target exposure values for the scene can be determined.
But of course you are right Don, how silly of me. Still, the meter will come in handy for incidence readings.
Josh Dahlberg is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon EOS Full Frame for HD

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 10:51 PM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network