Originally Posted by Boilermaker
I have seen nothing to make me believe that given identical settings there is any difference in the two channels. I believe that our problem lies strictly in the fact that we are unable to calibrate our projectors such that they both have perfectly flat gamma curves at the proper value from 0 to 100 IRE.
How are you testing for these "perfect gamma curves" ?
You may recall that I posted to this somewhere earlier to Athanasios, that one of the most important rules to blending is to make sure the top and bottom IRE's are properly calibrated in the projector before starting. Blending can be done a number of ways with you eventually getting fairly good results, but there's only one way to do it in respect to maintaining good or equal IRE levels from low to high.
I think the people who made these units intended for them to be able to match any two display devices. That's good for a lot of setups, but when dealing with High Performance Hometheater setups, you'll need to make sure things are very precise before you start with blending. When the setup is done right before blending, the blending is EASY. And not a task that could takes days to make happen, and after that tedious task, you'll have terrible gamma results.
First, you'll have to disable ANY gamma correcting devices at the projector, or after the blend device. If you're thinking you're going to tweak a matching gamma using two devices pre projector, forgot about it - it ain't gonna happen. It actually further screws things up
Next, the best way to check and confirm your pre-blending levels would be to use the various IRE windows (DVE). Choose any 6 of them and go through them one at a time to see how well your gamma is tracking between the two projectors. At this point, you're not using any gamma or blend settings. Only making sure you have properly matched both projectors.
I came to this conclusion just a few weeks ago. I had been using two separate gamma boost boxes that I scoped to make sure that they were at identical settings. Then I noticed from the screen shots from Athanasios that while he was having trouble in obtaining a perfect blend zone at both very high and very low IRE's at the same time, my situation was worse.
I then removed my two gamma boxes and recalibrated and found that it greatly reduced the anomaly such that it looked almost identical to Athanasios' situation.
Yep - as mentioned previously, won't work.
In our present setups (please jump in if you disagree, Athanasios) we can adjust the blend zone gamma settings such that we can have a nice seamless blend either at the high end or the low end, but never at the same time!
You'll have to make sure you setup both projectors first matching the low end IRE and then the top end IRE (100). But in doing this, it's very important to make sure that both projectors are set at the same lumens levels. In other words, you'll have to measure the light output at the low setup and then at the high setup. They both need to match with light leveled results. When that is done right, everything in between should follow. And the test for that would be the 6 or more IRE windows mentioned above.
If the top and bottom are properly calibrated, all should be well, but do remember that any gamma adjustments done at this point would have to be equal and would have to be an adjustment that exist for both outputs. The idea of having dual gamma adjustments sounds like a good idea, but only makes sense if using two different makes or model projectors.
Blending is really easy once you properly match the two projectors levels. From there, there's really no need for those sophisticated adjustments they add to some blend units. You should only need to tweak the blend zones for matching.
Therefore, I believe that if our projectors were perectly calibrated so that they had a near ruler flat gamma, the problem, would go away.
Ah, you're on this thing man..
Instead of ruler flat gamma. Go for an even IRE matching (6 or more IRE windows matching). Stay away from the word gamma, unless you've finished your setup and blending and it's time to tweak for low end gamma.
That is why I feel that if TVOne were to add full CMS, the problem would be solved.
Since all of TVOne's extensive scaler product lineup uses thir Corio2 system, I would imagine their entire product lineup would also benefit with a CMS at the same time, but this is pure speculation.
Does any of this not make sense to you?
Dude, you're almost at a point of helping them (TV One) make these device better. So far, you've giving them a lot to think about. especially since all the makers of these devices seem to not understand some of the things we both have raised here. It seems that they're selling the device with commercial application in mind, but somehow have included all the really neat features for HT. For HT blending, it's a whole different world.
For commercial applications, the goal is to put enough tweaks in the device to be able to blend any two display devices...
For HT, the goal is to precisely calibrate each mirrored (same make and model) projector to a properly
functioning blend processor.
When the blend is done right, the colors should match at equal lumens at almost every IRE reading. That means it would be able to do the very complex pastel colors as well. When that happens, It's blended!