Live data from Hacker News

Unbounded High Dynamic Range Photography Using a Modulo Camera

media.mit.edu

31–40 of 98 posts

Re: Unbounded High Dynamic Range Photography Using a Modulo Camera

#31
post #16

I had an idea similar to this that solved the oversaturation issue. Use 2 cameras. Have them at right angles to the shutter point, separated a few inches. At the T junction where the camera pointing would cross with the shutter area, put a prism there. The prism would give each camera 1/2 of the available photons. Now use any standard HDR processing technique.

prism = less than half signal at each end

Re: Unbounded High Dynamic Range Photography Using a Modulo Camera

#32
post #26

> No more will photographers or even ordinary people have to fumble with aperture size and exposure length. This is a "computer scientists" understanding of photography, and this phrase alone can even be seen as "dangerous" by photographers. There's more to aperture size and exposure length than "how much light reaches the sensor", like focus, depth of field, motion blur and bokeh, to name a few, that is not aknowled…

The Foveon sensor is different - the claimed benefit there has to do with stacked silicon and lack of debayering, and the benefit is having better resolving power with the same pixel count. Sony is now researching similar stacked chips so we'll probably see this idea return. The innovation with the tech in the article is in the dynamic range, current CMOS sensors have a fairly limited maximum dynamic range because of…

Indeed, I know what you've written and I agree with it -- writing it all in the first place would've resulted in a wall of text! I'm still unsure if there's a real benefit in this technology, or if the same result can be obtained by increasing the bit precison in the ADC stage of a "normal" sensor.

Even if there were, I pointed at the Foveon X3 as an example of a very good technology that was regardarded as a breakthrough but didn't really make it commercially. Another "revolutionary" idea that was marketed as something that "would change the way we take photographs" were the Lytro cameras, with their unique focus technology, that works by taking the picture in a different way than a classic camera, wich allows to change the focus of the picture working with the "raw" file. Even though that technology is also very interesting, it has remained in a niche market and only offered by one company -- more novelty than "mainstream" photography.

Re: Unbounded High Dynamic Range Photography Using a Modulo Camera

#34

The title here is terrible because over-saturation is an effect of poor tone mapping, which is inevitable if you want to display an HDR image in a low dynamic range display. An accurate title would be the end of over- exposed images, but why not just keep the original?

They're talking about the pixel brightness values getting saturated (255), not colour saturation.

But I've never heard over-saturation being used to refer to brightness saturation - brightness is either saturated or not.

Re: Unbounded High Dynamic Range Photography Using a Modulo Camera

#36
As a photographer who at times needed to deal with HDR this is great news. In the past, I had often wondered why some scheme like this wasn't possible. However, the title of this post is horrible. I understand they were trying to market it in a way it was accessible to most readers. That said, photography has become quiet popular and most people now understand HDR. So they could have just presented as true HDR with only a single frame image.

Re: Unbounded High Dynamic Range Photography Using a Modulo Camera

#37
post #27
post #25

Earlier quoted context omitted.

> there's simply no way to expand the camera sensor dynamic range without taking multiple exposures That's the point of this paper†. They expand dynamic range by having the detectors wrap around (discarding high bits) and then recover the high bits computationally. † here http://web.media.mit.edu/~hangzhao/modulo.html (linked by putterson in another comment)

I know, I just don't see how it solves this issue. You couldn't solve the issue before "fumbling with aperture size and exposure length" The only thing I would consider that solves "fumble with aperture size and exposure length" would be huge ISO range (both ways) without any noise. > No more will photographers or even ordinary people have to fumble with aperture size and exposure length.

> No mater how much you fumble with aperture and shutter speed there's simply no way to expand the camera sensor dynamic range without taking multiple exposures.

> I just don't see how it solves this issue.

http://rationalwiki.org/wiki/Argument_from_incredulity

Re: Unbounded High Dynamic Range Photography Using a Modulo Camera

#38
post #16

I had an idea similar to this that solved the oversaturation issue. Use 2 cameras. Have them at right angles to the shutter point, separated a few inches. At the T junction where the camera pointing would cross with the shutter area, put a prism there. The prism would give each camera 1/2 of the available photons. Now use any standard HDR processing technique.

Interestingly enough that's how Technicolor used to work. Three separate exposures from a single lens, split off by pellicle mirrors.

The downside is that like any pellicle you are dividing your light between multiple exposures, meaning you some mixture of a longer exposure, a faster lens, or more lighting. Technicolor required special high-intensity arc lighting. Also, the pellicles must be kept spotless because dust shows up on the final image.

Next-gen sensors will actually implement this physically - some receptor sites will be larger than others.

Re: Unbounded High Dynamic Range Photography Using a Modulo Camera

#39
post #20
post #11

Earlier quoted context omitted.

Sure, photographs will still control aperture and exposure time — this just removes a constraint at one end: if you want shallow depth of field and motion blur, you could use this method (and get extra bits) rather than an ND filter.

That's just really a completely misguided statement. No mater how much you fumble with aperture and shutter speed there's simply no way to expand the camera sensor dynamic range without taking multiple exposures. Besides I have never seen "ordinary people" fumble with aperture size and exposure length so that's a solved problem. Sometimes it gives "wrong" results, like exposing for the highlights rather than the shad…

Some DSLRs and MILCs (and I think some semi-pro compacts too) have a wide enough dynamic range that they can work and HDR image from a single RAW file. Catch is, you have to shoot RAW and then process it with specific software. When it's done in-camera, it always is through multiple exposures. Even without specific software, you can work the effect from a single RAW file to get "multiple exposures" from it and then combine them into an HDR image.

Re: Unbounded High Dynamic Range Photography Using a Modulo Camera

#40
post #24

> No more will photographers or even ordinary people have to fumble with aperture size and exposure length. This is a "computer scientists" understanding of photography, and this phrase alone can even be seen as "dangerous" by photographers. There's more to aperture size and exposure length than "how much light reaches the sensor", like focus, depth of field, motion blur and bokeh, to name a few, that is not aknowled…

It sounds from the implementation summary that it's equivalent to a higher bit-depth ADC, but that the higher-value bits are inferred by software somehow. I don't think it would properly recover an image with a dark field with the exception of a single pixel with a value of 10^7 above the dark noise. What would truly solve the dynamic-range problem is a logarithmic readout CCD. (Thanks for the Foveon pointer; it's an…

It's actually inferred by hardware - the paper handwaves it because they wanted to focus on the software, but basically they're talking about implementing a low-accuracy micro-ADC at every site that automatically wipes the charge when it hits a trigger voltage and counts every time it does so. Number of counts = site signal level.

Not quite sure that's practical or how you'd implement it on a destructive-readout sensor, though. Right now the sensors with enough accuracy and sensitivity are all destructive.

Post reply on HN