Dragons Den Photography project!

[cosmicma]

you both have a point ( mattuk and jet_kit ) and i would say most filters can be electronically emulated apart from neutral density filters especially something like a 10 stop filter

the problem with lowering iso levels is below a certain threshold the image begins to lose dynamic range hence not seeing many cameras with iso levels below 100 and in Nikon's case 200 iso

i would imagine that when you turn the iso levels or gain down to the levels required to emulate a 10x neutral density filter things would probably be looking pretty poor

[jet_kit]

Originally Posted by cosmicma

you both have a point ( mattuk and jet_kit ) and i would say most filters can be electronically emulated apart from neutral density filters especially something like a 10 stop filter

the problem with lowering iso levels is below a certain threshold the image begins to lose dynamic range hence not seeing many cameras with iso levels below 100 and in Nikon's case 200 iso

i would imagine that when you turn the iso levels or gain down to the levels required to emulate a 10x neutral density filter things would probably be looking pretty poor

Welcome to the big debate.

I remain to be convinced. When you add it all up the pixel (or to give it the proper term 'Photosite') has an electronic cover over it. When you activate the shutter the cover comes off and loads of little photons drop into the pixel's bucket. When the shutter closes the software counts the number of photons in the bucket and that determines the exposure value for that pixel.

Now, if your ISO is set to 400 and your shutter speed is 1/100 you would get the same exposure value than if the ISO was 100 and the shutter speed 1/25. If you think about it the shutter is open for 4 times as long, the aperture hasn't changed so you should get 4 times as many photons in the bucket, but you don't - you get the same amount because, effectively, an electronic 2-stop ND4 filter has been placed in front of the pixel cutting down the number of photons that land in the bucket. If we take this to it's logical conclusion ISO 6,400 (or whatever the top rank is on your camera) could be considered unfiltered, ND2 is generated to give us 3,200, ND4 = 1,600 etc. Until we get to ND64 for ISO100. It isn't actually as simple as that, but the principal is sound. and it works exactly the same way as putting a dark bit of glass in front of the light gathering device (Lenses to you and me).

If the software was capable of doing this for another 10 stops (and it probably isn't -YET) the overall effect would be identical to the use of a Big Stopper. In fact, it would be slightly improved because you will not have added two further glass surfaces to the mix. The main point is that the number of photons left in your bucket is the same. The question of losses in the dynamic range is a physical issue to do with photons bouncing around and landing in the wrong bucket. This is just as likely to happen with a 10-stop filter as with the above scenario because it's related to the amount of time the shutter remains open.

Good fun this, isn't it?

[cosmicma]

what you say makes sense but when were talking about is below the tolerance of the photosite ie below 100 iso
even on a canon 5d mk1 the iso 50 setting is really iso 100 with -1 stop compensation hence the loss of detail in the shadows and highlights
it seems to me that the minimum sensitivity/gain of current photosites is 100 iso ( 200 iso with nikon ) everything to do with lowering this figure is software
maybe there's a gain threshold were the photosites just fail to work properly ???
if a camera was developed so the minimum gain/sensitivity started at say iso 10 then your method would work

ok forget iso manipulation what about multiple shutter releases over time with mirror lock up on the same frame ( single shot ) calculated to emulate the desired effect of an ND filter of choice
rather than a complete redesign of the electronics behind the photosite this would be a basic change in software


do a search for "canon dslr magic lantern" you will see there's quite a bit of this sort of stuff already going on

[Markulous]

Ummm, well my humble little Canon G11 has a 3 stop ND setting and, whilst I have no idea how it works (but assume it turns down the sensitivity of the sensor), it just does work! Here it is in action, together with my ND Fader, in a 3 image blended composite (3 different shutter speeds to maximise detail - avoiding detailess 'silky smooth')



So quite why dSLRs can't have an in-built ND, I've no idea - a grad would be slightly more difficult but within the realms of possibility (after all, it's no different from a software gradient). I guess it's because you wouldn't see the result through the viewfinder but with Live View and EVFs.........

[OldBoy]

Except for the Sigma camera, all others only record images in shades of grey - not colour. It's the Bayer filter on top of the sensor which gives the infomation for the software to workout what the colour value of each photosite is.

[jet_kit]

Originally Posted by OldBoy

Except for the Sigma camera, all others only record images in shades of grey - not colour. It's the Bayer filter on top of the sensor which gives the infomation for the software to workout what the colour value of each photosite is.

You're right. I just didn't want to complicate the issue which is, after all, about sensitivity and whether or not we can artificial recreate a Filter (be it Colour, ND or Grad) in camera. I contend that it's within the scope of the Bayer Demosaicing (yes, it's spelled correctly) Algorithm. However, the two remaining questions are; is this possible within the constraints of the processing power on board and can it be done without introducing moire artifacts?

I have to confess ignorance on these two questions, maybe someone else ...?

[cosmicma]

Originally Posted by Markulous

Ummm, well my humble little Canon G11 has a 3 stop ND setting and, whilst I have no idea how it works

it's a real 3 stop ND Filter that moves between one of the lens elements so no real wizardry going on

it's a great photo by the way

[Cathus]

I think my head hurts

[Markulous]

Originally Posted by cosmicma

it's a real 3 stop ND Filter that moves between one of the lens elements so no real wizardry going on

it's a great photo by the way

Ah, that's how they do it! Thanks!

And thanks!

[GeoffWessex]

I'm not all that technically-minded, so I'm afraid a lot of the above was way over my head..... however, a question.... would it be possible, in the future, for a sensor's 'photo-sites' to, individually, amplify or reduce the amount of photons recorded? (a bit like each photo-site being able to say, "That's enough" or "A little more, please").

This would, if controllable, reduce high-contrast in shots and increase contrast in dull, flat lighting at the moment of exposure, and cut out the chance of completely burnt out highlights or pure black shadows.

(If you shoot Jpegs you can, of course, adjust the Contrast setting, but this is just a form of post-processing - if you're shooting Raw then the true 'original' would hold the information on its own, without having the camera's processor turn it into a Jpeg and make Contrast changes).

Just a thought - perhaps it could be called the 'Ansel Adams Filter'.