Originally Posted by craig john
Re-posted from the main RS-55 thread:
I had 2 forum members over last night to help me evaluate the A-lens vs. Lens Shift. Both guys have JVC projectors and A-lenses in their own systems. One of the guys does video calibrations, and he had calibrated the projector a week before, but without the lens in the path. The other guy owns an RS-20 that was calibrated by guy #1. We spent some time adjusting the A-lens for improved geometry. We then spent considerable time going back and forth on various content that included both very bright and very dark scenes. There was some delay switching from the A-lens to Lens Shift due to the time it takes to shift the image with the Lens Shift function, so this was not a direct A/B of the images.
Nonetheless, we unanimously agreed that the A-lens was better. The image was brighter and more detailed. In bright scenes, the added brightness was readily apparent, as was the increased detail. In dark scenes, we primarily saw better detail in the "shadowed" areas of the image. The Lens Shift image, while VERY good, was definitely not as bright or detailed as the A-lens image.
In answer to the question: "Does the RS-55 need an A-Lens?", I would answer that, no, it does not "need" an A-lens, but it can certainly benefit from an A-lens. If an A-lens fits the budget, it will be an improvement over Lens Shift.
PS. The calibrator is going to come back soon to re-check the calibration with the lens in the path. We'll take some readings with and without the lens. I'll post back then.
PSS. What I'm calling "Lens Shift" is actually called "Lens Memory". Sorry if I caused any confusion.
It's logical that the brighter image will reveal more detail, it will also raise the black level.
To test this correctly(detail) the brightness of both with and without lens need to be equalized.
Run the projector in high lamp without and low lamp with the lens in place. All things being equal, it is impossible for the A-lens to bring out more detail, it's a filter and will reduce detail getting to the screen, what is being observed is increased brightness raising the black floor revealing the hidden detail, the lamp on high without an A-lens will do that too and without adding scaling artifacts , ANSI CR reduction or A-lens introduced distortions.
If a colour correction is required with the lens in place, 2 cal setings will be required one for when the lens in not in the lens path(16:9).....unless one wishes to keep the lens in place all the time and loose 25% of the horizontal rez in 16:9 material.