Soft Edge Blend Workflow

[anthonydiehl]

I've been having some trouble getting a 100% perfect soft edge blend. I'm front projecting on a curved screen in this specific case, but I've noticed this is harder then I would expect even on simple flat surfaces. I'm using very high end 3-chip DLP projectors, 1920 x1200 native resolution on each, shooting onto a high contrast grey screen in a moderately dim environment.

The issue I'm seeing is two fold:

1. While the PB manual outlines how to use the Marker slider to locate where your blend begins, all users I have talked to say they do not use this marker and do not recommend using this. They all recommend just dialling all parameters in by eye.

2. Most edge blending systems I've used (in projector or software) incorporate a gamma, black level or curve adjust to get the dark or light banding in the overlap that often occurs dialled in. Basically getting the blend from 90% to %100 perfect. As far as I can tell, PB does't have something like this.

So, what is the recommended workflow here? Many users comment on PB having the "best looking blend" in a media server system, but thus far, I don't see how that is. Getting the blend to 90% is very quick and easy (Blend actually looks fine with textured photographic content). Get that last 10% to where it actually looks like a proper edge blend (appears uniform on solid colours)... much harder then I would expect.

One additional note. The curve on the edge blend appears to be a typical s-curve shape as it ramps down to black. However, when the curve % slider is reduced to a smaller number, it really looks like the beginning of the curve actually INCREASES brightness. For example, on a grey screen, if I dial in a blend on the right hand side on a projector and reduce the curve slider to a small number, the point where the curve begins to ramp down actually gets brighter before is starts ramping down to black. Is this normal? Gamma settings and custom gamma curves on the projectors are all defaulted and normal.

Tips, workflow suggestions, something I am missing?

thanks

[malkuth23]

The markers are great. Not using them is just macho nonsense. They mark EXACTLY where the blend starts and ends. This is exactly what you need to get the best possible warp. If the person best at warping in the world sat down to blend some projectors and did not use markers she might get close to the same numbers as the makers... But you can get it with almost no experience. Just use them. I use them every time and I have warper 100s of screens. It makes my life easier, it is accurate and quick and I am confident and 2 variables in an equation of 4. Simplifying a 4 variable equation to 2 is an enormous simplification.

The next part is to adjust the curve. This is where experience really helps. My recommendation is to start at 75% on both sides and work away from there. Little movements on each side. Switch between the 2 layers you are blending frequently and don't try to solve the problem with just the Left Softedge. The end results will probably be very similar numbers in both Left and Right.

The color of your content makes a big difference. Solid blue, BW gradient, 80%grey... there are many theories on this. Pick one, then try another. They all reveal different flaws.

The most important content is the content of your show. Check your blend in there. If it looks great, but solid blue shows a line then who cares?

Some cases will screw you no matter what. You want 20% overlap. Less than that is possible, but by the time you get to 10% your blend will be far from perfect. You want matching projectors with matching bulbs, with matching life. Anything other than this and you are already working handicapped.

Good luck!

[anthonydiehl]

Thanks Matthew, much appreciated.

So, do you recommend using the markers, setting them at the in points on both sides and then leaving them alone for the rest of the blend? Or do you typically come back and tweak this setting as well? Also, is the goal to use as much of the blend as possible and set the markers as far into the bland as they will go? Or would you normal only use a portion of the blend area and set the markers somewhere inside the overlap?

thanks,

A

[anthonydiehl]

Just following up on this and hoping that someone can shed light on this issue.

I followed a bunch of helpful suggestions from support and various users, but to no avail. All in all, I think I have put about 10 hours into this little blend alone, believe it or not.

I decided today to quickly try removing all blending in the software and compare the in projector edge blending, to at least gauge the appearance and if this projection scenario is just crazy difficult, of if I am just loosing my touch at blending projectors! I very quickly and roughly used the warp feature on the Braco HDX projectors to approximately line up the verticle edge that overlapped to line up more evenly. I then re-warped these outputs in PB Warper once the Barco in-projecotr warping had already been applied . Finally, I VERY QUICKLY dialled in the Barco blend. The difference was immediately obvious. I think I spent about 10 minutes on this blend.

Here is the blend I was able to achieve in PB. Note the brightness increase at the start of the blend. This artifact was extremely noticeable, even with only a single projector on.

PB_blend.jpg

Here is the Blend I was able to dial in with the in projector edge blend. Different angle but the same screen. (keep in mind that is was NOT a perfect blend and was only tried to compare the results I was achieving)

Barco Blend.jpg

I am sure that the Coolux system is more then capable of achieving good looking blends. So what’s going on here? I’d like to know for the future. The Barco guys seemed to think that the software was doing something odd to the curve of the blend. The curve definitely did not look right. The increase in brightness that is visible just at the point where the blend begins to fade down is not normal, not an optical illusion, and not usable.

I have achieved a solution for this project, but would really like to understand why this didn’t work out. Any ideas?

[simonj]

Most edge blending systems I've used (in projector or software) incorporate a gamma, black level or curve adjust to get the dark or light banding in the overlap that often occurs dialled in. Basically getting the blend from 90% to %100 perfect. As far as I can tell, PB does't have something like this

This would be such a great feature to add, as it would be REALLY helpful for those of us that have to work with crappy projectors. It would also be great to add cast adjustment to the softedges for those times when you can't adjust the colour balance. Are these on the development list?

[Patrick Verhey]

Hi,

we just build a new Softedge FX and a Gamma FX to solve that requests. Right now we are in testing phase but most likely they will be released with Version 5.7 by the end of the month.

Beside that 5.7 will bring a ton of new workflow feature, so maybe you want to download the release candidate and tell us what you think:

http://www.coolux.de/index.php?id=dowlo ... 0/file-235

But the mentioned FX are not yet implemented in that version....

best regards

Patrick

[malkuth23]

Even without that effect I have never had a problem getting a smooth blend as long as the projectors are close and the blend % is sufficient.
I am not sure where your issue lies, but it looks like you are not using the curve fader sufficiently. I suggest starting with these faders at 75% and tweaking from there.

[satanete666]

I am having same problem with edge blending , usually i do with spyder systen or with proyectors like roadster , but i am trying to make an acceptable blend with pandora and is impossible. When i put white there is a realy big diference betwen spyder and pandoras blending, any idea?