isco2 or panamorph UH480

[guyan123]

Hi

I have an isco 2 lens which at the moment i have never used as i have just bought a house so waiting to move before installing.
I have been offered a panamorph UH480 for a lot more then i paid for the isco lens and wondered if it would be a worth while upgrade.
I have a Optoma HD87 projector and the lens throw is not great and have been thinking the panamorph would be more better suited then the isco 2.
What do you guys think?

Cheers

 

[KelvinS1965]

Your short throw is going to be more of an issue that which if those two lenses will be better IMHO. A while ago I tried an experiment for another forum member and I moved my projector and Isco II to a short throw position to try it out. The image looked very curved and not as sharp as I'm used to from my regular setup. Even the mighty Isco III (or whatever it's called now) will give you this pincushion effect so it's worth bearing this in mind.

However as you haven't moved yet then perhaps you'll be able to have the longer throw setup? The Isco II is designed to be left in front of the projector all the time and a scaler used for 16:9 losing some resolution. I think the UH480 can be used with a slide, so you can have full res 2.35:1 and 16:9. I have to make a decision before putting a film on whether to set up my lens or if it's 16:9 film, then I have to slightly zoom to make up for the Isco II's 5% magnification effect.

 

[guyan123]

Thanks for the reply
When i move i do plan to have the projector at its longest throw which i hope will help with pin cushion and thought maybe the panamorph would help me in this regard.
Are you saying the isco II will be ok?
I keep thinking i should just get a big 16.9 screen and not worry about a lens but i would not be getting the height with 2.35:1 films which i think would be a problem for me.

Thanks

 

[abone]

The isco lens should be a far better lens cylindrical lenses are far better at achieving vertical and horizontal focus . With prism based lenses you have to change the first element specific to throw to achieve this. We have just installed a prismasonic cylindrical lens and thy are very very good especially for the money

 

[KelvinS1965]

Thanks for the reply
When i move i do plan to have the projector at its longest throw which i hope will help with pin cushion and thought maybe the panamorph would help me in this regard.
Are you saying the isco II will be ok?
I keep thinking i should just get a big 16.9 screen and not worry about a lens but i would not be getting the height with 2.35:1 films which i think would be a problem for me.

Thanks

The Panamorph will not have any more or less pincushion so I'm not sure what you mean regarding this. If you can setup at a long throw then this will minimise pincushion for any lens you use. Mine is so slight that I can still use a flat electric screen as there is maybe no more than 1/2" pincushion across nearly 10' width. This gets hidden by the screen edge (1/4" over in the corners and 1/4" under in the very middle is my preferance as this isn't noticable from my seated position.

The main issue for you is the size of the image where it hits the back of the lens. This will also depend on how much zoom you need to apply at the projector (ideally near minimum) and the size of the image chip(s) to some degree. Hard to really check without being in the room you plan to use, you could check if the minimum zoom would work OK, but that won't tell you too much if you can't see the image on a screen or wall to see if it's vignetting:

Align the Isco in front of the projector with it set to minimum zoom. Put on a signal such as an all white test pattern, BUT DON'T LOOK DIRECTLY INTO THE LENS. If you stand to the side (or below if it's shelf mounted like mine) you'll be able to see if the Isco is clipping the sides of the image. If this is OK, you'll be able to increase the projector zoom to see if there comes a point where the image hits the sides of the Isco (if you can project onto a wall then you might see the edges of the image getting cut off in a vignetting effect).

The good thing with the Isco II is that you can adjust the focus ring to optimism the sharpness for your particular throw rather than having to use a compensating front lens as some prism have. These compensating front lenses are designed to work for specific distances so you need to be able to setup at those throw to maximise the sharpness.

I don't have experience of the '480 but if it is a prism lens then I'd take an educated guess that the Isco II would be better. We're in the minority over here so you're unlikely to find someone using the same combination as yourself...hard enough to find another lens user these days.

 

[abone]

A good tip when looking into the lens to check for clipping is to put a sheet of white paper between the 2 lenses to defuse the light and you can still see the size of the image on the paper. If you are using a fixed screen slightly over scan to remove pincushion but a curved screen is best if you can afford it. Whatever you decide I think it is worth the trouble because a cinema scope image is the ultimate in home cinema.
Regards Andy

 

[guyan123]

Thank you for the informative reply's which has been very useful.
A couple more questions if I can.
Why is lens users rare nowadays?
What is the best way to work out the throw ratio for the lens?
I have thought about curved screens but after looking at the prices I think I will give them a miss plus my projector will be used in my living room so I have been looking at the dnp supernova and their curved screen are way too much money.

Thanks

 

[KelvinS1965]

I guess lenses are rarer these days as you can zoom a 1080p projector and for some the inconvienience of changing the zoom (and some projectors now have lens memory) is an acceptable compromise. Of course there are some that chose zooming over using a lens anyway. After all it's the cheaper option and for many the extra cost isn't justified.

I debated for a long time myself, but really it's one of those things that you just need to see for yourself to decide: I bought mine used for a fair price, so that if I hadn't been impressed with what it could do, then I could have sold it on at little or no loss. I've had it about 2-2.5 years now, so you can see how I feel about it. It's maybe my specific setup but because I'm at minimum zoom (on the end stops literally) I get less brightness from my projector, but also maximum contrast. The lens and screen gain still allow me to reach 12-14fL for scope images, which is generally considered a decent brightness to aim for (some go higher still though). Although I can't see the pixels there is still more density and I feel that the image just looks better for it. When I zoom I get a lift in brightness as the projector comes off it's end stop, but also I get the biggest change in contrast (it's not a linear change). So for my setup a zoomed image can be as bright, but it has maybe 30% less contrast (using Cine4home's contrast measurements as a guide).

Throw ratio is the distance from the projector to screen divided by the 16:9 image width (without the lens in place). So for my setup the figures are:

19' (228") from projector to screen.
16:9 image width 84".

228/84 = 2.7 throw ratio. Generally a TR of greater than 2 minimises pincushion and tends to give a sharper image (less lens area is used and well away from vignetting).

Hope this helps.

 

[Peter Parker]

Expense is usually the main reason, because a good lens can cost more than the projector that most people here would use.

Like Kelvin, after having tried both common methods to achieve CIH, I prefer using a lens, and the ISCO II was better than the prism lens I was using before it. The UH480 has a sweet spot of around 14 to 17 feet IIRC, but will perform better if used with a corrector element (astigmatism). The ISCO has an adjuster for astigmatism so should be sharper.

The advantage of the UH480 is that it has a larger aperture so will support shorter throws. You can calculate the throw by dividing the 16:9 image into the projector placement, so if the pj is 12 feet from an 8 foot wide 2.35 screen, the 16:9 portion is around 6 feet wide, so the throw is 2:1. What size 2.35 screen are you aiming for, and how far back will the pj be? How far will you be sitting from the screen?

Although a curved screen can help to eliminate pincushion, you can also eliminate it by overscanning the image onto the black border of the screen.

EDIT: Looks like Kelvin posted at the same time as me, and just beat me too it

Gary

 

[KelvinS1965]

Nice to see you back on these parts Gary. I see you're more familiar with the UH480, so at least the OP gets all the facts now.