Seeing colour in a B&W film..

[Harry Bloomfield]

I have been watching an occasional old film on 81 (Talking Pictures).

This morning there was a short BFI B&W kids film on (The Christmas Tree), from 1966, with kids involved in journey taking a Christmas tree to London. Rather oddly and despite it being a B&W film, the tree's foliage showed up quite faintly as green. None of the grass, nor the other trees showed as even slightly green. All rather puzzling, but I remember a TV experiment from way back, where they tested B&W TV's to hint at showing some colour. Anyone remember it?

I like watching some of these older low budget films, for the quiet roads and vehicles from the early days of my motoring career.

[Dave Plowman (News)]

A B&W TV can't show colour - other than that of its phosphor. Assuming you are talking old CRT sets - not sure I've ever seen a B&W LDC, other than tiny ones.

It might be possible to confuse the eye into thinking a part of the picture is in colour by using some sort of pattern. But that isn't the set producing colour.

[The Other John]

Yes, it was shown that certain flicker rates caused the brain to 'see' colour. An OXO commercial was shown and some people saw the gravy as brown and some as purple. It didn't catch on.

[Harry Bloomfield]

Dave Plowman (News) pretended :

The BBC conducted some experiments in the 1960's, I think Tomorrow's World might have been involved. Then of course all TV's were CRT, but I did see a slight hint of colour, on a B&W CRT. Some saw nothing as I remember.

[charles]

Tomorrows World showed something like that in the late '60s. Sadly, the film was American and intended to be shown at 24fps. In the UK showing it

25fps gave completely different results to the script

[tabbypurr]

Early CRT TVs were known to produce a pink picture when the EHT partially shorted, causing the current limiting red lamp to light behind the CRT.

NT

[michael adams]

I sometimes experience lemon tinted whites when watching B&W films on a modern TV, say when a character is wearing a white shirt - while all the other whites show up ok. Also sometimes the sky has a distinct lemon or mauve tinge.

There's a way around it by altering the settings although offhand I can't remember what it is. ISTR it may also be affected by the viewing angle.

michael adams

...

[Dave Plowman (News)]

Quite. Fooling the brain into thinking there is colour is an interesting trick. But unless consistent for everyone, a bit pointless.

[Chris Hogg]

also

[Dave Plowman (News)]

How early are you talking about? I've never heard of that one.

[Dave W]

Yes indeed. It used different mark/space ratios of flashing to make the effect. As a boy I made a spinning disc optical illusion which has four circular tracks with different ratios. There is a youtube demo of it here:

(fast forward to midway to skip the prologue).

[Nick Odell]

Others have talked about the psychological experiments with B&W TV but it crosses my mind that there could be lots of reasons why a solid-state colour TV has difficulty interpreting black, white and only greyscale in between, ranging from the set, the method of transmission and even down to the transfer from celluloid to digital in the first place.

Going back even further, the original B&W film stock may not have been true black on a clear-as-water celluloid base and different chemical processes can give different results. Guess who was given a copy of "The Book of Alternative Photographic Processes (Third Edition)" for Christmas?

Nick

[damduck-egg]

I think I remember it, I couldn't see any effect but there always some like my mum who reckoned they could. Did it involve in strobing the image at certain rate? There was a craze for looking at hidden images amongst a load of squiggles printed on paper about 20-30 years ago, I could never see those either but others found them quickly, OTOH as the printed pattern looked a bit like the ones sometimes printed on paper surrounding sensitive information such as a salary slip and we convinced a colleague that the within the pattern the company trade mark could be seen and he then announced he could see it I've been a bit skeptical as to how many were genuine.

BBC 4 returned to the subject in more recent times.

G.Harman

[Graham.]

On Sun, 31 Dec 2017 13:46:52 +0000 (GMT), "Dave Plowman (News)" coalesced the vapors of human experience into a viable and meaningful comprehension...

Not too sure myself, but on balance he is probably referring to a so-called "Barretter"

[James Wilkinson Sword]

Those were called surds or stereograms. No idea how you were supposed to see them, I just got vague instructions like "don't focus on it". I never saw anything but dots. I also never found any reason as to why an image should have appeared from random dots.

[NY]

I don't remember seeing it when it was originally broadcast. but I've seen a Youtube video of that item on the programme (it showed a drinks can with different "colours" on different parts of the can) and I saw a pattern, but no hint of colour whatsoever. It's possible that modern technology was hiding the effect: a) LCD screen rather than CRT, b) progressive scan rather than interlaced, c) it may have been a film recording of the CRT screen, rather than videotape, which would have destroyed the interlaced scan and altered the gamma of the image.

[NY]

I can't seen any hint of colour in the four different circles. They are different shades of grey, dependent on the differing mark:space ratios, and there is a quarter-circle sector that rotates (beating between rotational rate and video scanning rate), but no colour whatsoever.

Evidently I'm one of the people who can't see the effect. :-(

[NY]

That's a totally different effect: the eye sees colours (they are a negative of the correct colours) and the eye/brain tires of seeing those colours so when a black and white image is seen, the colour sensitivity of the eye varies for different parts of the image so the eye sees a hint of the correct colours.

The one that TW demonstrated used strobing or patterning to tire some of the cones more than others in the eye, so as to achieve that same goal of varying colour sensitivity of the eye.

[NY]

Another variable throw into the mix: not all black and white films on TV are the same shade. The film base may develop a slight colour tint as it ages, which leads to greys that may be very pale mauve or very pale green. You'd think that when B&W films were transmitted on TV, they would set R=G=B so as to achieve pure, untinted B&W irrespective of the colour of the original film.

[Brian Gaff]

Well so many issues here. I suspect if you had been watching it on a film projector you would not see any colour. What this may show is shortcomings in the digital technology or the way the three pixels of rGB affect ones individual eye and whether persistence of vision is greater on one of them for you, or indeed the actual pixel is on for longer. Back in the old days of analogue when I could see a bit I could get all sorts of strange effects due to inaccuracies in both the eye and the shadow mask of the tube and the registration of the colours.

If its derived from film there is that added issue of the frame speed vs the scanning speed and frame rate that it ends in and when it was converted and how. Many say that some old films are too contrasty, ie soot and whitewash effect blurring out detail in highlights or lowlights, all of which can upset colour balance of the eye. So I'm not surprised that some see such things but I don't think in these cases its deliberate. Of course it has been all the rage in and around the 90s to artificially colour black and white films by doing several frames in a sequence and then using 'tweening' software to interpret the rest of the shot to make it supposedly look real. Most who have seen these say that cartoons are OK but live action can take on the dream like look as the hues are subtly incorrect at times and of course if anything appears in a shot that has not been given a colour or cannot be tracked all sorts of odd things used to occur!

Brian