Originally Posted by noah katz
You can't validly make general statements like yours w/o quantifying everything, i.e you don't know how far his row of people are from what size screen, pj throw ratio, screen height, etc.
Of course you are right Noah.
I wasn't being super specific. It was a sort of generalized response to others who have made generalizations about the HP, e.g. that on axis the HP will be
high gain, but off axis it will be neutral gain so if you were planning on a neutral gain screen it's a win-win situation. It's not because, as per meticulous measurement supplied by Don Stewart (and used by Tryg in his HP thread) the HP goes below neutral gain (.95) by 20 degrees off axis and continues down to .57 gain by 60 degrees off axis. This coincides pretty much perfectly with what I see with my HP screen, including when I tape various screen samples (e.g. Carada at 1.1 gain) against it and walk off axis.
When I said that 3 people side by side can not see the same image/gain on the HP that's pretty much an objective statement, as per the gains measured by Don Stewart for the HP, in which the HP drops from 3.08 gain to 2.47 at a mere 5 degrees off axis and to 2.05 at a mere 10 degrees off axis. Those are visible drops and I can see exactly that as I move from the center seat to the next seat beside when watching the screen. In fact, simply shifting in my seat from leaning on one arm to the other arm...I can see the image luminance shift.
So while all 3 people will see a nice bright image, they won't see the same gain.
Originally Posted by noah katz
"And the other is that as you move off-axis you don't just lose gain, the image changes in other appreciable ways: you lose shadow detail, apparent contrast, color detail sticks out less, you lose apparent image sharpness
A screen is a passive device; from an objective standpoint, truly the only thing lost is gain.
Absent ambient light, all the other losses you describe are subjective and a function of the dimmer image and the way our eyes respond to it.
Precisely. That is what I'm getting at.
The claims made on behalf of the HP by people who own it are largely correct: increasing the brightness with an HP screen, even if you aren't actually increasing the contrast ratio, does have an impact on the image to our eyes
. I find, along with others, that in many scenes contrast does
appear more intense, I perceive
greater sharpness, more color detail and more shadow detail. It's all just easier to see in a brighter image. It's great stuff!
But when you move off axis and the gain lowers you start losing those perceptual gifts.
Some people have argued "well so what, all you are seeing off-axis is what you'd get with a lower gain screen anyway. So it's not like using a lower gain screen would be better in that regard
But as I'm trying to point out, that isn't exactly the case. Because due to how our eyes perceive images re brightness
a different screen gain is going to require a different projector calibration to maintain overall image quality. You are going to calibrate your projector differently with a lower gain screen.
For instance, using the HP material vs my wall (my wall being about neutral gain). On the HP screen I have the projector calibrated to look good from the sweet spot seats. In my case that has the projector in low bulb mode - high bulb is too much - with contrast/brightness/sharpness/color settings that make for an even looking image. Shadow detail is pretty much effortless to get on the HP.
When I move off axis to my side seats (anywhere between 25 degrees to 45 degrees or so off axis, as I remember), the gain goes down along with perception of image contrast, sharpness, and especially shadow detail. Like I pointed out in my Toy Story example: In the night time gas station scene, off axis seats lose almost all shadow detail (perceptually) and even all the stars in the night sky virtually disappear! The calibration just isn't right for those off-axis seats. But if I calibrated the projector to look right in the off-axis seats, it would require a different
calibration than I would want to use for the on-axis seats.
When I take the HP screen down and project on my wall, which seems to have an unlimited viewing angle, I bump the projector into high lamp mode to get closer to the HP vibe. Then I calibrate to get nice contrast/shadow detail etc for a nice, dimensional, even looking image.
Now the image looks exactly the same
no matter where I sit. In the front seats of course it isn't as bright as with the HP, but it still looks excellent and from the side seats it looks far better
than the HP does. It looks punchier, better contrast, depth, detail, shadow detail, the stars remain perfectly visible...you name it.
And that is the issue I'm high-lighting: that with the HP screen you can't do this as you can with a lower gain screen that has wide viewing angles. Because it drops gain appreciably off axis and because of how a dimmer image affects our perception of contrast/shadow detail/sharpness/color detail etc....you can't optimize the image calibration for all seats in most realistic seating arrangements. Because of this issue it's not the case, as some have asserted, that the HP will provide a similar image off-axis as if you'd simply gone with a lower gain screen.
That's all I was trying to get across.
I understand that lots of HP owners are fine with these issues. I think I may envy them in that regard.
I'm just pointing them out and as it happens it's something I really notice and would prefer not to put up with.
Joe Kane has championed this issue of wide viewing angles for quite a while too. The more I experience with projection screens, the more I can see why.