Goal: To fully test weather the RED one will achieve a perfect lock at various frame rates/timebases.
Main result: It never truly locks.
In Reality: In most cases your eyes/brain will never perceive it. Which is why many have gone ahead and shot 3D with the reds with very little issues from all but the most trained eyes.
If your still curious, read on…….it might get boring.
This all started sometime last year when I found myself involved in several stereoscopic Red one projects. One of them in involving lots of propellers and the other project had several high speed shots at different frame rates.
I embarked on doing a thorough test of the camera’s ability to lock.
The first camera we were using for one of the projects was a Sony EX3. Which has a BNC genlock in port. We tested several methods of genlocking the cameras. Besides my visual sync test we had a Specsoft RAVE unit at our disposal. With help from specsoft we were able to use a command line utility that could actually measure the difference in phase/lock of the 2 cameras. It would display what line the sensor was scanning on one sensor and then the other and then give you the difference. It did this continuously. The program kinda looks like a continuous ping if your familiar with that. Very cool.
2 out of the 3 tested methods resulted in PERFECT lock. 0 difference showing on a line by line analysis. Which was backed up by my visual tests. Thus proving my visual test method worked as a tool to accurately measure sync.
My visual test setup. (sorry for lack of pics, I’m on the road shooting)
I setup a large household cooling fan. The blades were black, so I put 1” white gaff tape strip on one of the fan blades. I set the fan at it’s lowest speed. I also used a Deneke smart slate (with the digital LED readout) to record the current clips settings.
Once recording, with this setup there was several visual ways of checking our frame lock of the cameras.
#1 – The famous slate clap.
#2 – At higher shutter speeds you could see the refresh of the LED redout of the slate. This turned out to be the most accurate method of checking sync. Since you would see half of a number in one eye and one quarter of that number in the other eye.(if they were out of sync that is)
#3 – The fan blade with the white strip. This provided a large visual representation of a fast moving object thru the frame and allow me to test how off the eyes might be if we shot high speed props on airplanes. Also I was able to learn how motion blur and shutter angle where hiding issues.
Using the command line tool in the rave I established my "control" of my process. Which was the EX3’s perfect lock and confirmation using every visual method I devised. (Congratulations Sony BTW.)
Once I had this to verify my method and tests I embarked on testing the REDS.
Cameras were placed side by side parallel, same setting, same lenses (red zooms) shooting the same tests aids I described above.
One of the things I wanted to find out was when I placed the cameras in various high speed frame rates the genlock icon (small padlock on the screen) would get a little non-smoking type sign over it. Clearly indicating to me I had lost genlock. I wanted to find out if that was true. It did give me a good genlock icon at 60fps and 120fps BTW. But wanted to see how bad was the sync when I lost the sync according to the Icon. Basically if the icon was an accurate representation of genlock.
For Genlock I used a AJA Gen10 with the switches at 1-2-7 ( also tried different switch positions giving me bad results so I stuck to that)
So to sum my test parameters I tested,
I ran the following tests @ 23.98
24,48,60,80,105,120fps @ 1/48th shutter
24,48,60,80,105,120fps @ 1/2000th shutter
I ran the following tests @ 24
24,48,60,80,105,120fps @ 1/48th shutter
24,48,60,80,105,120fps @ 1/2000th shutter
I re-ran those same tests parameters then using a Deneke TC/Sync gen device instead of the aja to see if that made a difference.
No difference in results from AJA. (also AJA is much cheaper so I recommend the Gen10, BTW)
At this point my results were already surprising. I discovered that technically speaking the RED One NEVER is truly genlock/phaselocked! Even when shooting at 24fps.
To clarify, the slate clap will match at 24fps. But a more detailed analysis at a higher shutter speed reveals there is a clear difference in images captured between the eyes! This is when analyzing fast moving numbers of the LED TC display on the smart slate.
For example. The slate clap would match but you will see half of a digital number 1 on the slate in one eye and a full number one in the other eye. Clearly demonstrating that each sensor is capturing images a slightly different time. Naturally this is an issue for 3D acquisition!
Furthermore, regardless of the padlock icon on screen there appears to be the same mismatch amongst all frame rates captured. So even with a valid genlock icon you will see a mismatch. Thereby making the icon irrelevant. So shoot at whatever frame rate you want since they are all off by the same amount.
Having tested 2 different sync generators, multiple frame rates and time bases. I turned my attention to the phase adjustment of the camera. To see if adjusting the phasing would assist in bringing the cameras scanning of the frame closer in timing.
Unfortunately the current phase adjustment at the time on build 21 was only 5 degree increments. Still I retested all the above listed parameters while adjusting the phasing of one camera -5, 0, +5.
After a few hours of testing and analysis the results were disappointing. Any phase adjustment brought the cameras even father from locking.
Being pressured from production to continue to look into this issue further I then drove down to RED HQ and had a chance to meet with and show Stuart English my test results on my laptop. First I wanted to know from him if my testing method was accurate and what his feelings were on the results..
Stuart reviewed my tests and agreed the the cameras were not truly locked according to my results. He promised to modify the next build with 1 degree increments on the phase adjustment to see if that helped. Other than that he told me that the scarlet would have a special cable that would allow for TC lock and perfect genlock of the 2 cameras. Great for scarlet/epic owners but not so good for us RED one owners.
So my thoughts after all this process?
Well in most situations (24fps, 180 shutter) the viewer will never be able to detect any issues. Motion blur hides any difference at that point. Which is why you have never heard any complaints after watching any RED 3D content.
The only time it * might * be noticeable is when shooting at higher framerates and narrower shutter angles. The narrower shutter angle reduces the motion blur allow your eyes/ brain to better record moving objects. Because of this when viewing 120fps material @ 24fps your eyes have more time to track objects moving thru the frame. Basically since you looking at the image longer your eyes will see the same object at a slightly different position during the same frame. Resulting in a bit of retinal rivalry and possible discomfort.
Then again it happens so fast that most people still might not notice it. Naturally when shooting 3D you need everything to be as correct as possible and to me Genlock is vital and is the building block of anything 3D that comes after it.
For me…..step 1 – get 2 cameras. Step 2 – genlock them. Only then worry about a your rig etc…
I would love to fix this issue and be able to achieve the same results I get with other cameras.
…..and yes, once the new build came out with the 1 degree increments of phase adjustment I did proceeded with a new round of testing.
Unfortunately the results were not satisfying and did not address the issue. There continued to be a difference.
I have held on to this information and posting this thread until the new build came out and I could test the new 1 degree increments. But now that it is out and it did not lock the cameras. I felt it was appropriate to finally bring this up to the community and possibly one again to RED’s attention. See if anyone had any feedback. Especially considering that with the new MX sensor I believe RED one's will continue to see 3D duty for years to come.
Anyone have any ideas? Might be a small annoyance to some but as I continue to shoot 3D RED productions one after another I just can’t reconcile the fact that I still do not have a perfect lock.
I want better.
If sony and others can do it, I’m sure RED can do it.
If RED is serious about 3D then need to address this issue. Perfectly locked cameras are just mandatory for 3D if you ask me. But since it’s not that perceptible we’ve been skating by without it.
So RED and others? What you think?