Barco sp4k 12

[Ricardo David]

Hello guys ,
We buyed this lazer barco lazer projector almost 1 year back, new from factory with One dead pixel, they changed the light engine, but the convergence is a Litlle off , and we tried several Times, but now ,maybe my eyes, i have a oled im my house now, i think there is some glow around white letters in dark , a some light leak ,like the aspect ratio dark bar glows up if the image is brighter up ou vice versa.is this normal?

[Steve Guttag]

Convergence on true RGB laser projectors, like the SP4K series is VERY difficult. Your eyes and normal optics will play tricks on you. Furthermore, it is nearly impossible to get red to converge with blue as they are at opposite ends of the spectrum.

Most of the lenses used for the SP4K were never designed for RGB laser or 4K and struggle with converging.

If you look at the literature from Barco, they indicate this:

Lateral lens color on edge of image
With 2K lens: 2 pixels average* ("C" lens)
With 4K lens: 1.5 pixels average* ("B" lens)

(* depends on lens, zoom, ...)

I have found that the Minolta lenses do better than the Fujion for the "C" lenses (in most all respects). The High Contrast lenses do better on the "B" lenses.

My best convergence on an SP4K projector is when there are two people on walkie-talkie or phone...one down by the screen, one operating the controls. Using a convergence camera or binoculars (or spotting scope) will fool you, particularly with red.

You may also notice as you walk from the rear to the front of the theatre, your perception may change (it does with me). I think we're working with primary colors that the simple optics in your eye just are not able to deal with. If the white lines look white, I'm generally good with it. You'll also find that once you apply the MCGD (corrected colors)...they are mixing colors as I'm sure the wavelength of the lasers may not be ideal as much as available/affordable. Heck, I find getting a good corrected reading to be tough too (Qualif Spectro).

[Marco Giustini]

Bom dia!

your glasses will also fool you, depending at what angle you watch the picture.

For the glow, I am not familiar with the SP4K series, are the engine output and back of the lens normally getting pretty dirty as before? Have you had that projector serviced by someone at some point?

Steve: 2 pixels! Wow!

[Marcel Birgelen]

Laser is the new NTSC... From Never The Same Color now to Never The Same Convergence...

[Steve Guttag]

2 pixels sounds like a lot but consider just how small they are and we're talking at the extremes of the picture. But, again, the "C" lenses were never designed for 4K...their MTF isn't there. It's great that Barco is offering the ability to reuse lenses but most of the "B" lenses also where not designed when 4K was a thing. I wish that there were HC "C" lenses like they have for S and B. Without a doubt, HC lenses look better though I'm not a huge fan of InVision...they don't hold their focus/zoom relationship as well as Minolta. I wish ISCO/Schneider jumped into the DLP lens market like they did with film but alas, that was not the case...just for PLF lenses with fixed focal lengths. Then again, I'm still a pro-anamorphic guy for constant height screens and would prefer if the larger pictures actually used more pixels from origination through projection. Of course, I like masking too.

[Stefan Scholz]

From the working principle, very narrow wavebands, and a single optic for all colors, it is nearly impossible to get a perfect convergence. The magnification factor is different over the different wavelengthes. With taking lenses chromatic aberration was know, it can be overcome by using a smaller aperture, and in digital taking by algorithms that know what to look for.
I have been told, wearing my eyewear, it will be next to impossible to converge, and should normally stay with the factory alignment. I will end up worse, that I start. At least the phone/ radio intercom and a second person.
What does help, is to go for the Ultra High contrast lenses (the ones with the smallest aperture and highest light loss, plus use 1.4 in chip based machines. That works pretty well, but in this case a 20 or more a 25 k projector is to specify with a "B" lens. Using this combination it works pretty neat.
With a small projector, HB high brightness "C" lens, you can't really get any better.