Does reducing brightness reduce lumens output?...

[Houldey]

It's a simple question, really. Let's say I bought a bright (1800 lumens) projector and I had a blacked out room. If I thought, wow, these 1800 lumnes are just too bright, would lowering the brightness setting on the PJ effectively be the same as owning a PJ with a lower lumen rating? If not, I'm confused why not.

It just seems odd to me that PJs would be made to output a specific amount of light, with no control over it, as it makes it even more hard to decide what PJ to get. It could be the case that for 6 months you want/need lots of lumens, then you need less. I know I'm speaking of lumens as though they are individual objects, but you know.

Anyway, if anyone has any idea about this feel free to reply.

Cheers,

H

[andy1249]

It just seems odd to me that PJs would be made to output a specific amount of light, with no control over it,

This might explain it a bit better ,

Lumen (unit) - Wikipedia, the free encyclopedia

Note the paragraph specifically on projectors ( ANSI lumens )

Quote:
ANSI lumens

The light output of projectors (including video projectors) is typically measured in lumens. A standardized procedure for testing projectors has been established by the American National Standards Institute, which involves averaging together several measurements taken at different positions.[5] For marketing purposes, the luminous flux of projectors that have been tested according to this procedure may be quoted in "ANSI lumens", to distinguish them from those tested by other methods. ANSI lumen measurements are in general more accurate than the other measurement techniques used in the projector industry.[6] This allows projectors to be more easily compared on the basis of their brightness specifications.[7]

The method for measuring ANSI lumens is defined in the IT7.215 document which was created in 1992. First the projector is set up to display an image in a room at a temperature of 25 degrees celsius. The brightness and contrast of the projector are adjusted so that on a full white field, it is possible to distinguish between a 5% screen area block of 95% percent peak white, and two identically sized 100% and 90% peak white boxes at the center of the white field. The light output is then measured on a full white field at nine specific locations around the screen and averaged. This average is then multiplied by the screen area to give the brightness of the projector in "ANSI lumens".[8]

Note the part in bold. This is where the figure is coming from.

[custard10]

Originally Posted by Houldey

It's a simple question, really. Let's say I bought a bright (1800 lumens) projector and I had a blacked out room. If I thought, wow, these 1800 lumnes are just too bright, would lowering the brightness setting on the PJ effectively be the same as owning a PJ with a lower lumen rating? If not, I'm confused why not.

you can't reduce the actual lumen rating but you can dim the projected picture if it is too bright.

this can be done by reducing the contrast which reduces the brightness of the brightest whites (peak luminance).

the brightness setting affects the darker portion of the image.

one of the the first steps in calibration is to achieve the optimal peak luminance (white level) for your room setting. so if it is too bright it is reduced via the contrast setting.

[KelvinS1965]

You will be throwing away the contrast ratio of the projector by reducing the contrast control to limit the brightness of the image. Far better to choose a projector that has a manual iris that can be used to reduce the lumens to match your requirements.

Another option is to use a Neutral Density filter (eg an ND2 will half the brightness), but you should buy a good quality coated filter otherwise it will reflect light back into the PJ which will reduce the ANSI contrast.

If you haven't got a screen, then try the PJ on a plain white wall first if possible: If you find it far too bright, you could buy a grey screen which will dim the image like an ND filter, it will also help give better blacks if the room has light coloured walls (reflection back to the screen washes out the image). If you have a total BatCave then a grey screen shouldn't be neccessary (or an overly bright PJ for that matter).

[custard10]

Kelvin - very true. there are other methods available to reduce brightness without affecting picture quality. the contrast setting should only be used for fine tuning the setup.

[kbfern]

Other methods of reducing brightness would be to wear sunglasses

[anibap]

Originally Posted by kbfern

other methods of reducing brightness would be to wear sunglasses

+1