Originally Posted by AV Science Sales 5
When I let the projector do the vertical stretch for the A-lens the image looked softer, not as sharp as when I used the Lumagen for the vertical stretch. I am only talking about the stretched image through the A-lens.
Yes, I understood that. When most people evaluate an A-lens they are going to compare an unscaled (1:1) zoomed scope image without an A- lens with a cropped and scaled (stretched) image via an A-lens, this introduces two variables, the lens and the digital scaling (stretching) system when the A-lens is in use.
Obviously the scaling system is going to have an effect on the outcome just as the lens will so what we see on screen is due to the combination of both, better scaling = better picture.
What I did differently is pass the video though a similar scaling path for both the A-lens test and the zoomed comparison test thus pretty much eliminating the scaling variable. I've probably got people confused by now so I'll explain, the process is as follows:
For the zoom test I take 1920x1080 scope format Bluray source and upscale it 200% to 3840x2160 with sharpening applied during the upscaling, then downscale to 1920x1080 and output to projector for display.
For the A-lens test I take the same 1920x1080 video, crop the black bars off leaving about 1920x810, then upscale that 200% with sharpening to 3840x1620, then downscale to 1920x1080 for output to the projector. The vertical stretch has now been performed so the projector does not touch the video and simple displays what it is given using all its pixels.
Both test images where displayed the same size on screen and since both the zoomed image and the A-lens image have undergone similar digital processing (double scaling) the comparison is a fair as it can reasonably be.
Double scaling the video as above significantly improved image quality and sharpness but we don't need an A-lens or a 4k projector to get this advantage (something the 4k projector vendors don't want people to know about). I normally use a 300% upscale these days (6k) for all Bluray content.
The lens I evaluated was very good as it had a negligible effect on image sharpness, but I could not see an advantage in using it as I don't use a large enough viewing angle for pixel structure to be an issue. By the time the image is large enough to see the pixels its too soft for my liking, data density is way too low. Using a 4k or sudo 4k projector will not help as no extra data is available from the source.