Wide Dynamic Range Myth

[BobDiaz]

No need 1 pair of pixels (ie 2 pixels) for getting 2 exposures. It's enough the electronic shutter, who can do it. I explained in my previous message. Like I said, these cameras don't have mechanical shutter, as dSLRs, but so-called electronic shutter, which is easier to work with.
The problem would be, in this case, that will require more powerfull processors to combine those different exposed frames, for the final result.

It could never be done with CCD image sensors, but with CMOS image sensors, the electronics can read the pixels like a RAM Memory chip. This would require the code to read all the odd numbered rows first for the short exposure and go back after a while and read the even numbered rows which have a longer exposure. You could have full resolution of the sensor in the mid tones, but both the highlights and dark areas would have 1/2 the vertical resolution. The image would have an odd look, because the dark areas would have an odd motion blur and the mid tones to white areas would look normal. No question that all the extra steps would take more processing power.

 

[jokiin]

Simplest solution would be just use two cameras, have contemplated doing this, one with great day quality and one that's great for night, easy to do but not sure how commercially viable it would be

 

[DashCamMan]

What I still can't get my head around are all the terms related to Dynamic Range. There are the following:

Wide Dynamic Range: Not sure what the dB number this has to be for it to be Wide Dynamic Range

High Dynamic Range: A technique where the camera captures more than one frame, each frame has different dynamic range, and the camera combines the different frames to produce one WDR frame. Not sure if this is related to dB or not.

Perhaps Marketing terms only:
Fuzzy Dynamic Range
Ultra-Wide Dynamic Range
Extended Dynamic Range
Active Dynamic Range
Super Dynamic Range

 

[jokiin]

The last 6 are pure marketing spin to try and rename an existing technology to try and sound like you're doing something different to your competitors

 

[Dashmellow]

Simplest solution would be just use two cameras, have contemplated doing this, one with great day quality and one that's great for night, easy to do but not sure how commercially viable it would be

What you describe sounds similar to one of the surveillance cameras I have on my building which features two lenses and two sensors. At night it switches to a dedicated B&W image and this scheme is quite effective. It is an older camera but in some ways it outperforms more modern cameras I have that have newer sensors and more modern, sophisticated DSPs. A miniaturized version of something like this might be interesting is a dash cam although I imagine it would probably add to the manufacturing costs to build such a camera.

The CCTV camera I'm talking about looks similar to this one.

 

[jokiin]

OK I see you got what I meant, wasn't sure if I explained it clearly or not, a few different ways this could be done, maybe something we'll look at later, if the technology hasn't caught up by then that is

 

[Dashmellow]

Speaking of dual lens dash cams, I stumbled on this oddball unit I've never seen or heard of before.

 

[jokiin]

That's the concept, not how I would do it though

 

[Dashmellow]

That's the concept, not how I would do it though

No. I wouldn't imagine. It looks kind of hideous. The idea this camera employs is interesting though. One lens is wide and the other is of longer focal length to capture more detail.

 

[jokiin]

No. I wouldn't imagine. It looks kind of hideous. The idea this camera employs is interesting though. One lens is wide and the other is of longer focal length to capture more detail.

Yes concept has merit, the execution is unusual to say the least

 

[WJM]

Not sure whether this is the best matching thread on this forum, but since it comes out on top in a Google search on 'dashcam wdr', I'll give it a chance anyway....)

What seems partly missing in this thread, as an indicator/analyzer for what is (multiple-frame) HDR/WDR and what not, is that the frame-rate is split in half (could be more, when/if more frames than two would be used, but I have yet to see that performance in any non-super-high-end camera).
(limited by both sensor/light-sensitivity and processor, I assume)

So instead of having a todays state of the art 60fps (in non-HDR/WDR mode), it would fall back to 30fps effectively (if not, the camera might be technically capable of 120fps....).

This change applies to both the non-dashcam camera's I know having this feature; the previously mentioned EOS 5D-II, plus more interestingly, the Casio range of EX-ZR camera's, starting from ZR200....interesting, because its HDR-video is not ordinary HDR, but HDR-Art, and a very impressive one as well.
(but, not just half the frame rate, but also only 720P, instead of full HD (and all that at 15fps (normal video is 30fps))
(indicating that more than just the frame rate, either sensor read-out or processor capacity is running against its limits too)

PS, apart from this same-era discussion (2013), I don't see any obvious later/current discussions?

https://dashcamtalk.com/forum/threads/patriot-f3-with-shdr-super-high-dynamic-range.1296/

(haven't searched yet; perhaps Google only showed this one for having the most external links, to this forum, on sites/groups elsewhere?)

PPS, while contemplating using a ZR200 as a dashcam, I started wondering how to apply permanent power (from 12/24v) through it's USB->Casio-propriatary cable....as it doesn't allow the camera to be activated when charging....but that might be just for the purpose of data-transfer, not necessarily for charging....so, before hacking this cable, are there any USB-plug adapters that change a data+power cable into power-only?
(never looked into that category)


Btw, in the Casio forum on Dpreview, it was stated that the Casio HDR-Art Movie technology is not from Casio itself, but from an external source/company, and probably for that reason only a rather black box, that hasn't seen any performance changes in the 3 years since the ZR200.
(sadly also excluding the otherwise even more interesting Tryx (EX-TR100 and upwards), with 21mm (equivalent) lens)
(probably different sensor, not suitable for this HDR-Art Movie (although all other HDR-Still modes are equal to the rest of the ZR-Series (3-digit only, AFAIK), including HDR-Art-Still (suggesting that only the Art-Video mode was and is outsourced)

 

[jokiin]

PPS, while contemplating using a ZR200 as a dashcam,

non dashcam products rarely work well for this task, not generally designed for endless hours of running, loop recording, auto start, event recording etc

 

[Street Guardian USA]

+1 if you want dashcam functionality and set-it/forget-it reliability, buy a dashcam.

 

[WJM]

Oh yes, I do see all the limitations, most critical probably that of thermics, both the sensor all by its own, plus solar heat.
Plus a lousy 15fps & 720P.

But unless someone shows me a dashcam wit HDR-*ART*, I won't budge....)

Even as a regular point & shoot, this functionality is still non-existent elsewhere.
(and that 3 years after introduction)
(but the same freezing of time & technology is with this 15fps/720P, just as inexplainable)

Just watch the only a few(!) good amples on Youtube ('casio hdr-art'), especially those in twilight, and/or with artificial lighting....

Oh, also lousy when handholding: no stabilisation....either not possible for the twin-frames, or again proof that the processor runs at its limits.....

(oh well, for (bonejarring or seasickening) offroad, I am pondering about a stabilizing gimbal/pod anyway....)

Watch thos video's, and please notify me when *any* new camera has this feature.....)

Btw, this isn't even about eye-pleasing visual art *only*....overall image contrast is very nicely enhanced, very helpful to spot details/shapes/objects, especially in twilight or just on those dull/rainy/grey day's....
(and you get the white clouds/blue sky without the lightloss of a polarizer....)

PS: for the 21mm HDR-Art-Stills, I will probaly end up with a dashmounted Tryx also, one day....)
(the Sony HDR-Paint shots are way less impressive; only their Illustration mode might be fun, but not in video-mode currently, sadly)

 

[jokiin]

YouTube is the worst place to judge but what I see there so far is not impressive at all, even if it were class leading video it's of little help if it can't perform the functions needed reliably or takes manual intervention each time

 

[russ331]

When I was trying to decide which dashcam to buy, I briefly tried my pocket digital camera (Casio Exilim EX-H5) as a temporary solution.

It was immediately apparent that, without loop-recording mode, the Casio would record for only around 25 minutes. Restarting the camera while driving the car was a dangerous distraction, & I abandoned the experiment after an hour.

There's no substitute for a proper dashcam. Pocket cameras don't have the necessary functionality.

 

[DT MI]

When I was trying to decide which dashcam to buy, I briefly tried my pocket digital camera (Casio Exilim EX-H5) as a temporary solution....

I did the same a few years ago using a Canon S3-IS wedged between the dash and windshield. Interesting as a first experience but nowhere usable as a dash cam.

 

[WJM]

YouTube is the worst place to judge but what I see there so far is not impressive at all, even if it were class leading video it's of little help if it can't perform the functions needed reliably or takes manual intervention each time

Well, the same search words would also work on vimeo or any other better behaving video site of course....)
(but even on Youtube the samples are rather scarce, so smaller sites might not help much, or at least not offer much more samples)

And lacking both loop recording and g-sensor/crash-loop-protection, it could never be a full replacement in security/insurance context of course.
But my wish list in that context even excludes loop-recording, for wanting to have full 100% coverage of any kilometer of road I travel, to counter both vague insurance claims and questional traffic fines (both speed- and behaviour-offenses).
And for this day-in-day-out downloading of full 100% video coverage, after each trip/day, I have not seen any smart/automatic solutions yet (automatic connecting to a file-server at home, be it WIFI or otherwise.


Bottom line however: the regular camera industry does a more interesting job of enhancing contrast/colour (that's the Art in HDR!) than the dashcam sector.
Even though it's just a baffling single manufacturer only, and just as baffling is that neither Casio nor any other regular/P&S camera manufactuer offers ordinary HDR-video....only HDR-Art-Video, and only Casio.
(and none goes beyond the very minimal set of 2 images....by now, 3 years later, one would think that both sensors and processors gained enough to increase that number to 3 images)

PS: that 25/30min limit is bad too of course (legal ****, to distinct between stills- and video-camera (event-regulations, in particular car-racing!)), but just as for that USB-(data-)plug blocking normal operation, some cable-wise hacking might be tempting....)
(none of the Casio ZR-series offers (IR-)remote control AFAIK, so the hack will need hardware skills & more cable....)
(probably hacking into both power-on and button-release)

 

[Nigel]

...What seems partly missing in this thread, as an indicator/analyzer for what is (multiple-frame) HDR/WDR and what not, is that the frame-rate is split in half (could be more, when/if more frames than two would be used, but I have yet to see that performance in any non-super-high-end camera).
(limited by both sensor/light-sensitivity and processor, I assume)

So instead of having a todays state of the art 60fps (in non-HDR/WDR mode), it would fall back to 30fps effectively (if not, the camera might be technically capable of 120fps....).

...

The only reason for the frame rate being "split in half" is that your Casio doesn't have sufficient processing power to maintain full frame rate.

In the case of the mini 0806,

First of all it always uses WDR/HDR, it is not possible to turn it off.

Secondly, assuming it is night time the frame rate will be 30 fps (if you have it set to 60 fps then it actually records 30fps when it is dark to get a brighter exposure), the 30th of a second will contain something like one exposure of a 35th second, one of about a 350th and one of about a 3500th. That almost fills the 30th second and allows correct exposure for everything from the shadows to full headlights (although not quite HID headlights), the 3 exposures are then combined and recorded while the exposures for the next frame are being collected. During daylight the same thing happens, even if using 60fps which is genuine 60fps during daylight.

The result looks natural enough that most people will never realise that it uses WDR which is as it should be, you don't want dashcam footage looking arty, you can always do that in post processing on your computer.

 

[WJM]

The only reason for the frame rate being "split in half" is that your Casio doesn't have sufficient processing power to maintain full frame rate.

In the case of the mini 0806,

First of all it always uses WDR/HDR, it is not possible to turn it off.

Secondly, assuming it is night time the frame rate will be 30 fps (if you have it set to 60 fps then it actually records 30fps when it is dark to get a brighter exposure), the 30th of a second will contain something like one exposure of a 35th second, one of about a 350th and one of about a 3500th. That almost fills the 30th second and allows correct exposure for everything from the shadows to full headlights (although not quite HID headlights), the 3 exposures are then combined and recorded while the exposures for the next frame are being collected. During daylight the same thing happens, even if using 60fps which is genuine 60fps during daylight.

The result looks natural enough that most people will never realise that it uses WDR which is as it should be, you don't want dashcam footage looking arty, you can always do that in post processing on your computer.

Okay, now it starts getting interesting, with more facts than I had at hand....)

First, regular HDR, be it video or stills, shouldn't look artsy all, at least not by itself; the 'Art' factor is based on rather wilful tweaking (color mapping).
(IIRC, without any tweaking at all, the combined images will look dull/flat)


Second, your sequence of 1/35 - 350 - 3500 is a real (possible) sample?

Because also in terms of light stops difference, this seems a bit higher than what I recall from the EOS 5D-II with Magic Lantern software upgrade, more than just the 3 instead of 2 images.
(I first thought it might be surprisingly high, but 10x equals 'just' the 3stop-something that is common in most on-board HDR-processing)
(leaving most photographers wishing for (much) more, at least by having more frames than 3)
(only the high-end EOS camera's like 1D(s) & 1V cover an (auto-bracket) of 9 shots x 3 stops = 18 stop spread, instead of the 6 stop spread above)


Last but not least: you suggest doing the artsy work (color-mapping) as post-processing on PC.
But that requires the full/clean access to each of those 3 individual images, not the combined/sandwiched endresult, as is present in the camera, as video file....sadly....)
(you might still be able to do some tweaking that looks like HDR-Art, but then it's the same 'fake' stuff you can also get from single-shot high-dynamic images)
(of course, storing all 3 images with video increases data volume by a factor 3 also, so it is something every manufacturer should avoid like the plague....)
(data-compression within that set of 3 might seem just as straightforward as the compression between 2 frames with normal video-compression, but for proper post-processing, you want RAW images to begin with, not downgraded JPEG/MPEG/etc....)

Anyway, interesting, thanx; first time I see it mentioned that 3 images are used, instead of 2.
Any insight whether this only applies to Mini 806 and similar sensor/chipsets, and/or which others definitely only do 2 images?

PS: more than 3 stops between each frame seems not to be implemented anywhere, so I guess that might be the practical limit....however, that is also a conclusion/deduction based on current or even older sensors, not having as much single-image dynamic range as modern ones today....and if the single-spread/-coverage is higher, then the gap between them can also be increased, because the 2/3 images keep overlapping anyway (so no image detail is lost between the 2/3 shots).

Thanx!....)