Tutorials

A bit about Projection

Observations on Projectors.


The projector is not the only thing that governs what you see when your image is projected.

The Room
We project in a room with a white ceiling, white walls and a shiny floor.
We project on to a white screen specifically to reflect the light.
This means that there is plenty of light flying round which reflects back on to the screen unless the image has no content! In spring we will also have much more light leakage.

The Screen
We have changed from the Avonway wall screen as it was too close to the ceiling and there was a large amount of reflection back on to the screen. This causes a loss of contrast as no projector made can suck light off the screen when it wants black.
The Avonway screens are also not flat which can produce a brightness variation in areas which should be evenly illuminated.

The Black in the Image isn't Black (The Brain)
No sorry it isn't and never will be. All projector technologies, that I know of, let some light through.
Even if the projector was perfect the room is going to dominate and blacks will not be black. That is unless Avonway would permit us to paint floor, ceiling walls, black and completely light seal the windows, remember spring cometh. Taken a bit further we would need to ensure we all wore dark clothing! :-)
So why do some images have good blacks? Well that is due to the fact that you are a human and your eye/brain isn't actually an absolute instrument but it is a very good relative instrument. If the 'black' is adjacent to a white area, it will look black.
An example of this is in a presentation projection in a daylight lit room with a text filled page it will appear that we have very black text against a white background. In absolute terms the black will not be black as it is illuminated by the daylight in the room, in relative terms your eyes should decide the text is very black!
OK so if you have an image with black edges which doesn't fill the screen then the image will drift off into the unlit portion of the screen. A judge recently pointed out that a white pencil line around a dark image would 'hold it in', it will also make the blacks look blacker.
An advantage of the new projector is that it is brighter than the old projector and should be less influenced by stray light.

The colours don't match my monitor (Hard One, technology, Brain?)
There isn't a rule anywhere that says it should and that would also require that every monitor of every member produced identical results. As the owner of two good monitors I can assure you that matching them is not as simple as profiling them the same way. That does not produce an identical match. So if we cannot easily match two adjacent monitors then matching all the monitors in the club will be nigh on impossible and therefore so is the exact match to the club projector.
This is not an excuse for an incorrect profile and the club takes seriously the requirement to profile well.
That said there are particular problems.
With an image where a large proportion of the image is a subtle shade of white then small changes of the white point will affect the 'feel' of the image a lot.
We have to learn about the new projector but we customarily profile to the native white point.

From the X-Rite website
When we profile monitors, photographers usually select “D65? as the white point for the profile. With projectors it’s usually best to select “Native”. We do this for several reasons. First we are not setting up the projector to match print output so the white point setting is less critical. Second a projected image in a darkened room allows our eyes to “correct” any small difference in the native white point of the projector and our normal “D65? viewing environment.  And most importantly, any change in the white point off the “Native” setting will result in a reduction of luminance.  This is generally not desirable and can degrade the overall appearance of the image and reduce the enjoyment of those viewing the image. Rarely is any setting in colour management an absolute so you may find situations where the white point is so far off that setting D65 and the resulting loss of luminance is more desirable than a brighter image at a dramatically skewed white point.  So keep this in mind and use “Native” as a guideline for general use and not an absolute.

I got John to profile his SX60 to D65 and the results were not good, back to Native.
So with a picture without a lot of subtle tones the eye will adjust the white point and the picture will appear correct. An example is if you have two monitors with subtle white point differences then an image on one will appear white after a period. If you drag it on to the other monitor the whites will change depending on the new white point (say blue) slowly your eyes will adjust and the whites will look white. Drag it back and the whites will appear red at first and then change back to white. Your brain has just interfered with your perception of colour. This also gives a problem if the change of images during projection is fast as a tone cast from one image can carry over its compensation to the next image.
Although the eye brain combination is not good at absolute colour there are things that it is good at. Test images for monitors, printers and projectors will include a range of skin tones as we are pretty good at comparing skin tones and seeing if the colours are incorrect. We are also pretty good at recognising greens that are not real!

The colours don't match my memory (Brain)
In an immediate compare the brain eye combination is very good however once memory is involved it is not good.
It is also unlikely that the judge will look at the projected image and remember the colours of your subjects when you took the picture. He will however probably recognise false skin tones or false greens.

What do I do to get the best out of the projector?
If you are unhappy with the results that you achieve then that needs to be looked at. As a club we can arrange to have the projector set up say during a practical evening and allow you to see the results before a competition. That would allow you to decide if the image projected well or needed adjustment. Not all images are best projected, not all best for print and my work flow is different depending on my output. So if you are concerned then solutions exist.
Please note that some members are sending images in for projection using aRGB. This is a concern as the software make an arbitrary change of colour space and therefore results are not necessarily controlled. If you need help on colour management please ask a mentor.
Remember we do our best, we don't always get things right but together we should be able to make things better.

If you think there are factual errors in this tutorial please let me know, point me at the correct information source and I will read, learn and correct.
I know I am not a colour expert.
Rex