Does increasing the zoom decrease PQ?

[Anthony P]

Originally Posted by Flatnate

OK, back to brightness, first, this two to one range of brightness isn't true for all projectors. The huge shift in brightness occurs with projectors that are exceptionally flexible in placement, by virtue of wide range zoom lenses.

When a projector's lens is in full wide angle mode (largest image from a given distance), more lumens make it out the lens. In full telephoto, less lumens.

Many projectors for the home, (mostly 3LCD and LCoS types) now offer 2:1 zoom lenses. That is a placment range from closest to furthest, of 2 to 1. Perhaps, for a 100" diagonal 16:9 screen, that might be from 10.5 feet to 21 feet away.

don't you find it odd that lumens would be directly related to zoom in magnitude no matter the lenses involved (and so projectors with less zoom will automatically have less discrepancy?

that is what I pointed out. If the guy is measuring at the lens (which is almost a given at this point) his numbers would make sense but they don't show what he (and you) are saying.

To put it simply, (and I will use metric to make it easier since there is no conversion involved) If I have a source that is X Candela and it is spread on Y meters square I get X/Y C/m2 of brightness if on the other hand the area is doubled it will be X/2Y and image brightness will be ½ as bright but the light output (X) will be the same.

The issue is that a photometer has a given area, so it will measure how much light hits that area, it then uses that to tell you how many lumens/candela it is receiving. You can't check image size with your eyes at the lens ( way too bright and there can be damage to your eye, but you can cheat a bit), if you have manual zoom, WHILE THE PROJECTOR IS OFF, look through the lens and see in both wide and tight (or vice versa). What happens on tight the black hole looks bigger and wide it looks smaller. The same will happen with the image (bigger image for tight and smaller for wide). And so the photometer captures less of the tight image and more of the wide one and so it sais the tight is less bright while wide is brighter. BUT if you put your projector at one end or the other or the middle of zoom so that the image size on your screen is the same then the tight image will grow less and the wide more and so everything will equal out again.

[Anthony P]

Originally Posted by v_squared123

Optical zoom would be me twisting the lens cap to make the image bigger or smaller and digital zoom would be using the zoom-in function of the projector where the black bars of a cine scope movie would be removed and i can also change the scope of format from 4:3 to wide,etc. Is that the difference? And if so, according the earlier post above using the digital zoom function of the projector would mean you would lose pq clarity as opposed to using the optical zoom of the projector by twisting the lens. Is that correct as well?

yes, more or less. High end projectors might have power optical zoom and no twisty lens cap, and there was a time when projectors had very little resolution and were not too bright and so digital zoom could be used for more than just eliminating black bar.

[Anthony P]

Originally Posted by Flatnate

The calculator at Projector Central says that for the VPL-VW15 has a 1.6x manual zoom lens (what you twist by the lens cap). The lens throw calculator on the site states that you have a placement range between 12 feet 1 inch and 18 feet 4 inches to produce a 120 inch diagonal picture. So positioning the projector at 12 feet 1 inch would produce the brightest possible image for that projector.

I can't be bothered to do the calc and I am guessing you did it right. But my recommendation is to never go to either end. Just because if things are a bit off it can be more than a bit annoying. So if it is between 12.1 and 18.4 I would say go somewhere in between (and if he wants to believe such nonsense as the brightness will be eaten at the zoom when can always stay close to the 12.1 while not being there). The issue is that peoples measurements are not always exact and manufacturers stuff are not always exact so it is a shame when you screw things up because of a few inches.

[Flatnate]

Originally Posted by Anthony P

I can't be bothered to do the calc and I am guessing you did it right. But my recommendation is to never go to either end. Just because if things are a bit off it can be more than a bit annoying. So if it is between 12.1 and 18.4 I would say go somewhere in between (and if he wants to believe such nonsense as the brightness will be eaten at the zoom when can always stay close to the 12.1 while not being there). The issue is that peoples measurements are not always exact and manufacturers stuff are not always exact so it is a shame when you screw things up because of a few inches.

Agreed, and with a 1.6x zoom lens on the Sony, the range from closest possible position to the furthest is even less than other projectors; and any light loss from the optics would be even less than other models as well. Its not worth chancing for something like 5% of your brightness in this case.

[v_squared123]

Guys I've been doing a lot of reading on anamorphic lenses and motorized zoom lenses and I'm curious to know something. Since its possible to use an anamorphic lens to fit a 2.35 scope screen without zooming in, is it possible to use an anamorphic lens to fit a 2.35 scope film on a 16:9 screen by horizontally compression and use the lens to vertically stretch it thereby filling the 16:9 screen? And im asking about that method since you cant vertically stretch a 2.35 image and then use the lens to horizontally stretch it without going off the 16:9 screen. Just trying to figure out if there is a way to use a 16:9 screen for both; formats anamorphics lens or zoom lens. Also, do ppl use anamorphic lenses bc their projectors do not have zoom available? Why else would you use one? Isn't it true that using the zoom method on ur projector doesn't cause any loss of resolution and that you lose some amount of brightness? What's the point of spending thousands? Panasonic made a wonderful product that automatically zooms in for you when set!

[v_squared123]

Anyone?

[v_squared123]

If there is a sticky for this already just let me know!

[kurtis21]

You can't use an anamorphic lens on a 16:9 screen. It defeats the purpose...you will still have black bars on top & bottom...or if you streach the image vertically...everyone will appear tall & skinny on your 16:9 screen. You need a 2.35.1 or 2.40.1 screen for an anamorphic lens to work prpoerly...or use the zoom feature as you said. I personally use the zoom feature on my screen and don't see any loss of resolution or brightness. My projector has 5 save settings for this feature for all of the different screen sizes...and works quite well IMO!!

[Flatnate]

A sticky that shows how a vertical compression or a horizontal stretch anamorphic lens works would make a great sticky. I don't think I saw one up there. Maybe I can work on that.