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Distortion on TV camera lenses?
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PostPosted: Thu Jul 07, 2022 9:30 am    Post subject: Distortion on TV camera lenses? Reply with quote
Something I have been wondering about for quite a while:

When I look at my television (a perfectly flat panel these days Wink ), I can't help but notice that many TV programs (BBC News, Sky News, Sports, documentaries, you name it) very frequently show images with really quite significant levels of pincushion distortion;

- Wimbledon Tennis: base line at the bottom of the screen bent like a banana. The stands at the top of the screen bent the other way.
- Downing street 10 shot in the news: heavy pincushion distortion in the brickwork wall

These are just two examples, but the list is endless. And it is almost always pincushion distortion, even on more wide-angle shots. Now, we are likely talking some pretty pricy TV camera optics here, so why is the distortion at a level that, compared to photographic lenses, would place them right in the bottom tier??? I mean the levels of pincushion distortion displayed in these TV programs are really pretty horrendous compared to those seen in 1980's budget photographic zooms even...


PostPosted: Thu Jul 07, 2022 12:53 pm    Post subject: Reply with quote
The TV zoom lens may have more distortion than the primes. For the primes, the Taylor Hobson Ortals 1.1/2/3/5 inches have very good distortion control from the samples i see on the web.


PostPosted: Thu Jul 07, 2022 1:02 pm    Post subject: Reply with quote
maybe the lines would straighten on a crt tv (not that anybody uses those anymore)


PostPosted: Thu Jul 07, 2022 2:47 pm    Post subject: Reply with quote
D1N0 wrote:
maybe the lines would straighten on a crt tv (not that anybody uses those anymore)

I wonder if the curvature of the screens in early crt tvs are all the same.


PostPosted: Thu Jul 07, 2022 3:40 pm    Post subject: Reply with quote
I do find telephoto pincushion distortion to be a giveaway of 'old' as much as chromatic aberration, although that wouldn't be as obvious to audiences.

And whilst it looks awkward to stick CA on everything, I am forgiving as you need a visual cue. Everyone must accept/understand in their various hobbies for shortcuts to be made.


PostPosted: Thu Jul 07, 2022 4:02 pm    Post subject: Re: Distortion on TV camera lenses? Reply with quote
RokkorDoctor wrote:
When I look at my television (a perfectly flat panel these days Wink ), I can't help but notice that many TV programs (BBC News, Sky News, Sports, documentaries, you name it) very frequently show images with really quite significant levels of pincushion distortion;


Perhaps you are more sensitive to distortion than the average person! Laughing

Seriously, I think lens makers and television broadcasters don't care about distortion because TV is action, people don't pay much attention to still-picture details.

The lenses used in TV have a large zoom ratio, from 20x to 100x, it is practically impossible to design such a lens with negligible distortion. A typical TV zoom lens usually only covers the telephoto range, so the distortion is almost always pincushion type.

Today, the TV lens market is dominated by just two manufacturers, Canon and Fujifilm. These people are very comfortable with the virtual monopoly of the market. It certainly wouldn't be too difficult to implement distortion correction by software in their lenses. But who cares?

Speaking of high sensitivity to distortion, one thing that intrigues me in photography is how many people are highly annoyed by small amounts of chromatic aberration. Often the background is completely out of focus, but if the eye sees slight colored fringing on an out-of-focus branch, this is enough to condemn a lens.


PostPosted: Thu Jul 07, 2022 4:39 pm    Post subject: Reply with quote
There maybe something to the CRT screen curvature- I recall reading about it somewhere years ago- either Popular Mechanics, or Popular Science.

At one time, T.V. cameras came with a set of primes on a wheel plate- even cameras for location work.
That would be an interesting acquisition.

I watch the goal posts on televised NFL games, just to catch the distortion.
Another place is the grid-iron.

-D.S.


PostPosted: Fri Jul 08, 2022 1:15 am    Post subject: Reply with quote
Yes, there was a real effect of screen curvature on TV screens, and TV cameras of the time were made
to take advantage of that.

I remember reading about the Sony Trinitron TVs, and how they were based on a cylindrical diameter
as opposed to the concave TV screens of similar time. If I'm remembering correctly, this led to
one of the first steps towards pushing the US to begin adopting higher standards for
North American broadcast standards, which somehow specifically state that the broadcast standards
must always coincide with capabilities of advancing technology. I'm not sure how it's implemented,
but it's a regulation which exists.

Now, there's regulations on the books in the US that broadcasters must meet technology to a certain extent,
which is why we've finally adopted HDTV and higher standards while lagging behind the rest of the world.
On the flip-side, we've got streaming services to overtake broadcast.


PostPosted: Fri Jul 08, 2022 8:32 am    Post subject: Re: Distortion on TV camera lenses? Reply with quote
Thanks for all the replies so far! Thank You Dog

Gerald wrote:
Perhaps you are more sensitive to distortion than the average person! Laughing


I am sensitive to it yes in terms of noticing it, but not in terms of minding it too much (if that makes sense Wink )

Gerald wrote:
The lenses used in TV have a large zoom ratio, from 20x to 100x, it is practically impossible to design such a lens with negligible distortion. A typical TV zoom lens usually only covers the telephoto range, so the distortion is almost always pincushion type.


To me this sounds like the most likely explanation. I do sometimes see shots (e.g. Wimbledon tennis) where the camera shows a remarkably good quality
detailed shot of something in central London which I know to be miles away from the camera position, and then they zoom out ... and keep zooming out ... and keep zooming out ..., until we are left with a fairly wide-angle shot of the camera location itself. So yes, these lenses do seem to have quite a large zoom ratio. Perhaps that leaves them with noticeable pincushion distortion throughout most of their zoom range.

Gerald wrote:
Today, the TV lens market is dominated by just two manufacturers, Canon and Fujifilm. These people are very comfortable with the virtual monopoly of the market. It certainly wouldn't be too difficult to implement distortion correction by software in their lenses. But who cares?


Unfortunately you are right; monopolies do stifle some types of innovation (technical mostly, "innovation" in planned obsolescence on the other hand thrives under monopolies Sad ).

Gerald wrote:
Speaking of high sensitivity to distortion, one thing that intrigues me in photography is how many people are highly annoyed by small amounts of chromatic aberration. Often the background is completely out of focus, but if the eye sees slight colored fringing on an out-of-focus branch, this is enough to condemn a lens.


There are many "photographers" who actually first look for the lens' imaging flaws in an image before they notice the quality of the overall image (if they ever get to admiring the image that is, some stop at the lens' flaws...). The majority of lens "flaws" that are highlighted in tests and are obvious when you look for them in an image, have negligible impact on the final artistic quality of the image.

Learn to accept them as the relatively insignificant flaws that they are, and your choice of usable lenses increases by several orders of magnitude! Wink


SkedAddled wrote:
Yes, there was a real effect of screen curvature on TV screens, and TV cameras of the time were made
to take advantage of that.

I remember reading about the Sony Trinitron TVs, and how they were based on a cylindrical diameter
as opposed to the concave TV screens of similar time. If I'm remembering correctly, this led to
one of the first steps towards pushing the US to begin adopting higher standards for
North American broadcast standards, which somehow specifically state that the broadcast standards
must always coincide with capabilities of advancing technology. I'm not sure how it's implemented,
but it's a regulation which exists.

Now, there's regulations on the books in the US that broadcasters must meet technology to a certain extent,
which is why we've finally adopted HDTV and higher standards while lagging behind the rest of the world.
On the flip-side, we've got streaming services to overtake broadcast.


Yes, Trinitron TV's had a different electron gun, mask and screen curvature arrangement which made them, frankly, a bit better.

I am baffled by the popularity of streaming services; all those $10-a-month subscriptions add up! Most of it seems pretty dire content to me with just one "must-have" popular production per provider... So far I am staying clear of streaming services, both with TV and music Wink


PostPosted: Fri Jul 08, 2022 10:51 am    Post subject: Reply with quote
Wide angle pans make me nauseated


PostPosted: Fri Jul 08, 2022 12:31 pm    Post subject: Re: Distortion on TV camera lenses? Reply with quote
Gerald wrote:
RokkorDoctor wrote:
When I look at my television (a perfectly flat panel these days Wink ), I can't help but notice that many TV programs (BBC News, Sky News, Sports, documentaries, you name it) very frequently show images with really quite significant levels of pincushion distortion;




Speaking of high sensitivity to distortion, one thing that intrigues me in photography is how many people are highly annoyed by small amounts of chromatic aberration. Often the background is completely out of focus, but if the eye sees slight colored fringing on an out-of-focus branch, this is enough to condemn a lens.


I am bothered from chromatic aberration since the day that I realised that they give a green cast to the background of the tele shoots, while, for instance, the pictures taken with my old Apo Telyt 180 keep a remarkable neutrality.


PostPosted: Fri Jul 08, 2022 12:33 pm    Post subject: Reply with quote
D1N0 wrote:
maybe the lines would straighten on a crt tv (not that anybody uses those anymore)


Just a little humor about the evolution of televisions and man: Laugh 1



PostPosted: Fri Jul 08, 2022 12:51 pm    Post subject: Reply with quote
I've stopped watching tv except for Formula 1. I haven't noticed any distortion but the zooming they can do is quite spectacular.


PostPosted: Sun Jul 10, 2022 6:49 pm    Post subject: Reply with quote
I was watching wimbledon and noticed that the lines were perfectly straight. I wonder if its your TV


PostPosted: Sun Jul 10, 2022 6:59 pm    Post subject: Reply with quote
IMHO that TV lenses were designed for CRT curvatures is utter nonsense.


PostPosted: Sun Jul 10, 2022 7:11 pm    Post subject: Reply with quote
philslizzy wrote:
I was watching wimbledon and noticed that the lines were perfectly straight. I wonder if its your TV


Well, its a recent flat panel LCD screen so I really doubt it is my TV...
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