HDR technique applied to Super 8

[reflex]

I'm guessing that most people around here know what High Dynamic Range photography is. It typically involves taking a burst of a shots with bracketed exposure and then digitally combining them to produce a single image. The effect can be stunning, although it can also make the world look like it's made from plastic. Here are a couple of examples.

A slightly overprocessed view of Parliament in Ottawa. As with many outdoor HDR shots, the light on the stonework looks articifical, as if it's been rendered.


I like the HDR aesthetic more when used indoors, especially under challenging lighting, although it does add a certain gothic sci-fi feel in this case:


The effect is usually achieved using a DSLR with automatic exposure bracketing, but someone recently posted on the HDR Flickr group about achieving an HDR effect from a single film negative. Several people promptly made fun of him, but the technique makes sense because film has much broader latitude than a CCD sensor. An HDR effect can be achieved by using a film scanner to combine multiple passes of the negative with different exposure curves.

I'm wondering what it would look like to do this on a larger scale by regrading a properly Telecined motion picture scene multiple times and then combining each frame to produce an HDR image. The end result could be quite interesting, not to mention bloody time consuming.

[Scotness]

Related discussion earlier:

viewtopic.php?t=14760

[reflex]

Not only that, but I participated in it. :oops:

Now, has anyone seen my car keys??

[christoph]

well, using HDR scanning for a negative doesnt really make sense as the negative itself has a very low contrast range. multi-pass scanning for lower noise is sometimes worth it though, specially with cheaper units.

for telecine of reversal film, HDR is a good idea in principle since the contrast range of a reversal film is higher than most ccds can capture. however, the big problem is to get results that still look natural. i gave up the idea of HDR telecine for my unit after a lot of testing because of that reason.

here's a test i once did with some samples from fred
note that he since has much improved his setup and get much better results by just doing a single capture.
++ christoph ++

[VideoFred]

Now, has anyone seen my car keys??

Under your desk :lol:

Here's an example (HDR Avisynth plugin): 1968, Agfa


Of cource I could have captured that scene more bright, but then the white parts at the left where blowing out.

More examples here:
http://users.pandora.be/ho-slotcars/HDR

Fred.

[christoph]

Here's an example (HDR Avisynth plugin)

if i understand this correctly you're still using a single frame as a source, no?
in that case it would be more precise to call it a "shadow restore plugin" or so, because it's not really higher in dynamic range, just clever recalculationg of existing dynamic range ;)

which brings me to an idea...
photoshops new "shadow/highlights" adjustment should work very similair.

jup, it does:

++ c

[VideoFred]

if i understand this correctly you're still using a single frame as a source, no?
in that case it would be more precise to call it a "shadow restore plugin" or so, because it's not really higher in dynamic range, just clever recalculationg of existing dynamic range ;)

Yes, single frame capturing.
The author calls it HDR, but you are right of cource.
It restores shadows. It is very useful for film transfers.
But it only works if there is something to see in the shadows

Hey! That photoshop plugin does the same indeed. 8)


Fred.

[wado1942]

I use color curves to achieve a similar thing. To stretch details out of the shadows and highlights is fairly easy with curves because the detail is there in the extremes of the exposure, it's just somewhat crushed together. I do that with video too if the camera had a bias light in it but it only works for the shadows.

As for multipass telecine, a friend of mine transferred a 16mm film we shot to video using that method of combining 3 different exposures through a home transfer w/ video camera. I must say that the lattitude in the video is excellent but the clarity is not good. The tiny bits of jitter & gate weave rather ruined the process because it was slightly different on each pass.

[christoph]

I use color curves to achieve a similar thing.

i once thought so as well, but if you take fred's sample and try to get to the same results using curves only you'll see that it's something quite different.

As for multipass telecine, a friend of mine transferred a 16mm film we shot to video using that method of combining 3 different exposures through a home transfer w/ video camera. I must say that the lattitude in the video is excellent but the clarity is not good. The tiny bits of jitter & gate weave rather ruined the process because it was slightly different on each pass.

you really need to do the three different exposures in one pass, ie before the film transports to the next frame. it will imporve things if you use a camera camera that just cant handle a reasonable contrast, but it will never match the results of a transfer on a device with higher dynamic range.

++ christoph ++

[Scotness]

Here's a few interesting links:

Searching around about that photoshop plug in - I came to this interesting discussion which led me to these two products:

Light machine and
an HDR plug in

both are designed to work on single shots, rather than multipass images - but both give pretty amazing results - this is from the Light machine shadow correction gallery





I'm pretty impressed - here's some other plug ins they make too

Scot

[mattias]

My shadow highlight gamma plugin for fcp does something similar. See previous threads as well as my homepage. The beach has totally worn me out, i think i must relax with another skol before i go for some brazilian beef and samba all night. :-) Até lôgo! /matt

[mattias]

dp

[VideoFred]

Is High Dynamic Range possible at all in digital systems?
I mean... 0 is black and 255 is white.

Should we not need a 0-510 scale or something?
Is the dynamic range not limited by the digital system -like it is for now-itself?

However, I did more double capture tests lately.
On some scenes, it is the only way to get all the visible information from the film transfered to digital, without blowing out whites.

The strange thing is, the histogram shrinks horizontal :roll: instead of expanding. It looks like I am pressing all the info into a very narrow range. But pure visible it looks very fine.

Fred.

[Scotness]

Is High Dynamic Range possible at all in digital systems?
I mean... 0 is black and 255 is white.

Should we not need a 0-510 scale or something?
Is the dynamic range not limited by the digital system -like it is for now-itself?

Yes you need a scanner or imaging device that can record at greater than 8 bit colour depth - which quality scanners (especially negative ones) can do.

Scot

[VideoFred]

I see...

Color depth is the most important factor for HDR.
Blown out whites is something different, then.

But then the analog signal must have the most information..
The bottleneck is the A/D converter.

Fred.