Chromatic Correction and Inexpensive A-Lenses - AVS Forum

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2.35:1 Constant Image Height Chat

blastermaster's Avatar blastermaster
02:50 PM Liked: 140
post #1 of 6
04-02-2013 | Posts: 1,037
Joined: May 2005
So, I've been reading up on the new Cinevista lens and the Chromatic Correction that comes with certain projectors. I've mentioned a few times in this forum that I have a HTB lens with the correction element. The element works to a degree, but I definitely still notice CA at the edges of my screen. Am I right that apart from noticing purple fringing on text that it also contributes to the loss of focus at the edges? I would love to get a new fancy lens, but it's just not in the cards right now (damn the home renos!). If this correction will work on the new Cinevista lens it should also work for any lens that has chromatic aberration, should it not? I'd eventually like to get the U480 or some similar variant but again I don't have the funds for that right now. I'm thinking that if a lot of the newer projectors come out with this CC feature it may eventually trickle down into more budget projectors. Here's hoping.
John Schuermann's Avatar John Schuermann
08:14 PM Liked: 68
post #2 of 6
04-02-2013 | Posts: 2,347
Joined: Apr 2003
Focus and chromatic aberration are two different things. With aberration, all three color images are sharp but misaligned. That shouldn’t be confused with focus error even though misalignment might be perceived as blurring.

Yes, the chromatic correction built into certain projectors will correct for aberration in other lenses as well. However, it is my understanding that the HTB lens does not have astigmatism correction, which is a focus issue. Chromatic correction will do nothing to correct for focus.

Keep in mind that I have never seen an HTB lens in action, so I could be wrong about whether or not is has astigmatism correction.
CAVX's Avatar CAVX
04:14 AM Liked: 48
post #3 of 6
04-03-2013 | Posts: 8,391
Joined: Aug 2005
Quote:
Originally Posted by John Schuermann View Post

However, it is my understanding that the HTB lens does not have astigmatism correction, which is a focus issue. Chromatic correction will do nothing to correct for focus.
AFAIK, they started out as Home Theatre Brothers with trophy prisms and then moved onto a proper optical finish surface and when they changed their name. These new prisms were made from BK7 only, so not CA Corrected. They then made a prototype set of CA corrected prisms which they claimed were designed with Zemax by san optical designer. Photos of the prisms were posted on their blog, but there was no screen caps that I remember seeing. They never took them into production either. They did however produce something they called UACE (Universal Astigmatism Correction Element). Hope I got the name right and that seems to be as far as their "Anamorphic Research" took them rolleyes.gif
blastermaster's Avatar blastermaster
07:59 AM Liked: 140
post #4 of 6
04-03-2013 | Posts: 1,037
Joined: May 2005
Thanks, CAVX. It's lookin' like I'm just going to have to ante up and get a good lens, although I'm not giving up hope on finding a good used one.
Kelvin1965S's Avatar Kelvin1965S
01:18 PM Liked: 48
post #5 of 6
04-03-2013 | Posts: 3,255
Joined: Apr 2007
If you're lucky and have a suitable throw then I'd recommend the Isco II if you find one for sale. Has all the corrections you need (Chromic and astigmatism) and no worries about having a projector with the pixel shifting feature, so you're more flexible in your projector choice. I use mine with a JVC X35 as per the pictures thread you saw.

Fingers crossed you come across one. smile.gif
blastermaster's Avatar blastermaster
12:03 PM Liked: 140
post #6 of 6
04-06-2013 | Posts: 1,037
Joined: May 2005
Thanks, Kelvin. Gonna keep my eyes out for that one and perhaps the UH380. I've seen B stock ones go for a price that I can live with (read: wife approval). wink.gif
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