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03-11-2015, 01:39 PM   #16
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QuoteOriginally posted by VisualDarkness Quote
Building it into the lenses would be a lot more expensive in the bigger lenses and would either be controlled by hand or needing an extra contact to communicate with the body.
Could be... but I am not saying which one is better or not... the OP thinks that it is in the camera G12; whereas the ND filter feature is integrated in the lens which can of course communicate with the camera. However, the challenge in the DSLR would be quite different.


Last edited by aleonx3; 03-11-2015 at 02:32 PM.
03-12-2015, 02:40 AM   #17
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QuoteOriginally posted by VisualDarkness Quote
Building it into the lenses would be a lot more expensive in the bigger lenses and would either be controlled by hand or needing an extra contact to communicate with the body.
This does not have to be as complicated as it sounds. Pentax has made lenses with built-in filters several times in the past.
Most of the Pentax lenses here have built-in filters (or in the case of the large telephotos, drop-in filters - I couldn't figure out how to filter them out from the results, or the Q lenses for that matter). I can't imagine there's any reason that an ND filter wouldn't work in much the same way. They could probably even do a trio of ND filters bult into a lens.

I'd like to see those in any fast (I mean, faster than f/2) lens.

But in the camera body? Probably not possible.
03-12-2015, 03:34 AM   #18
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My physics is probably not up to scratch here, but I have often wondered why the sensitivity of arrays/bands of individual light wells couldn't be manipulated to give the same result as an ND or variable ND filter. I'm thinking that the voltage output of each sensor could be somehow modified to achieve various levels of response to the same light level, or to maybe detect overexposed areas and provide reduced output.

Hopefully someone with a few more functioning little grey cells than me could chip in and explain the error of my thoughts.
03-12-2015, 11:57 AM   #19
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QuoteOriginally posted by wizofoz Quote
My physics is probably not up to scratch here, but I have often wondered why the sensitivity of arrays/bands of individual light wells couldn't be manipulated to give the same result as an ND or variable ND filter. I'm thinking that the voltage output of each sensor could be somehow modified to achieve various levels of response to the same light level, or to maybe detect overexposed areas and provide reduced output.

Hopefully someone with a few more functioning little grey cells than me could chip in and explain the error of my thoughts.
I think you just invented the way cameras control ISO.

03-12-2015, 12:14 PM   #20
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QuoteOriginally posted by Mistlefoot Quote
I am not sure what you are trying to say here other then what we all already know and I commented on in my initial post....

I am asking, if you want to build a physical ND filter inside an SLR would not a better approach to look into ISO 50 or ISO 25. SLR manufacturers tend to offer ISO 25600 or ISO 51200 as a selling feature (use in low light). Why don't the same manufacturers offer ISO 25/50 for the opposite reason (bright light, slow shutter).

Is it a limitation of chips? or just not something that is needed as photographers can overcome bright light with filters, low light, not so much......
A very interesting question. I dont have the absolute answer but some thoughts to share:
- The sensor system is used in its operation region. An example can be seen here , where in picture four a II marks the operation region. To get into this region a bias voltage gets applied.
- If you lower the bias the signal to noise ratio can get worse, like It is mentioned in this abstract ( where the optimal bias is said to be around 100 mV for their setup).
- High ISO values are used for marketing (as you said), thus (industrial) engineering focussing on this direction seems likely. Many customers dont even have a clue what this value means, but bigger must be better
- Lower ISO capabilities might call for new sensors, which could loose on the high ISO side.
- Low ISO could be a unique selling point for the reasons you mentioned. Limitations in the electronics might prevent it, but the market ("advanced" photographers) could also be too small.
Would be interested in more information about this aswell.
03-12-2015, 12:18 PM   #21
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I think the whole "electronic" ND filter is not a real thing. You base iso is what it is. If it is iso 100 and you just expose as though iso 50 was your max, odds are you will get blown out highlights.

As to the whole built in ND filter, the issue is that the lenses are bigger than for these small sensor cameras and I don't really see any way to build it into the camera body itself. Adding a ND filter to a DA 40 would probably increase its size, while it wouldn't be used in the majority of situations. Probably easier to let folks buy their own and use it when they think they need it.
03-12-2015, 12:51 PM   #22
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QuoteOriginally posted by delegopa Quote
Lower ISO capabilities might call for new sensors, which could loose on the high ISO side.
This is an excellent post, I will only add that the physical dimensions of micro-circuitry limit the amount of current that can pass through it, which limits the dynamic range of the sensor. The camera is programmed to vary the sensor's bias voltage according to the light intensity measured by the camera's metering system, but as you mentioned there are noise limits. If you are designing a new digital camera you have to decide which end of the light intensity range you want to improve on and going for better low light capability is a no-brainer, because the user can always reduce sensitivity with filters, but there are no filters that help to increase sensitivity. A 2 stop optical ND filter gives you the equivalent of ISO 25 without compromising the low-light sensitivity of the camera.
03-13-2015, 02:57 AM   #23
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QuoteOriginally posted by narual Quote
I think you just invented the way cameras control ISO.
Thanks for the response, but ISO is dealt with evenly across the sensor, I'm talking about bands of ISO sensitivity to emulate an ND grad filter. In other words varying the voltage output of groups of sensors. Maybe something similar to luminosity masking in Photoshop - but then again, this would require some sort of sensing of light levels.... I'm just speculating here.

Not exactly the same as the the way cameras control ISO, but related.

My question is - is this feasible/ practical? What are the pitfalls and downsides?


Last edited by wizofoz; 03-13-2015 at 03:28 AM.
03-13-2015, 12:49 PM   #24
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QuoteOriginally posted by wizofoz Quote
Thanks for the response, but ISO is dealt with evenly across the sensor, I'm talking about bands of ISO sensitivity to emulate an ND grad filter. In other words varying the voltage output of groups of sensors. Maybe something similar to luminosity masking in Photoshop - but then again, this would require some sort of sensing of light levels.... I'm just speculating here.

Not exactly the same as the the way cameras control ISO, but related.

My question is - is this feasible/ practical? What are the pitfalls and downsides?
Not precisely. It depends on your settings.

Nikon calls it Active D-Lighting and Sony calls it DRO. I'm not sure if Pentax's highlight correction works the same way or not.
The company who owns the technology and licenses it calls it Adaptive Digital ISO:
QuoteQuote:
Adaptive Digital ISO

ISOAD is an advanced shooting mode suitable for D-SLR users. Instead of simply increasing ISO to increase sensitivity when a long exposure is not suitable, ISOAD automatically calculates the optimal ISO value for every pixel in the image, within a predefined range. Using high ISO captures dark details but leads to increase in global noise and blow-out of highlights. Instead of ISO 1600, use ISOAD 1600: the camera calculates the optimal ISO value for each pixel of the image, up to a maximum value of 1600. The result is a dramatic increase in the effective dynamic range of your images.
But yeah, that's not the same as a grad filter. But since the possibility is there for it to adjust iso on a per pixel basis, maybe it could make one.

Wouldn't it be incredibly cool if the DSLR screen had a touchscreen, and you could swipe it with a finger and have it use edge detection to outline a digital grad filter nearly perfectly?
03-13-2015, 02:59 PM   #25
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QuoteOriginally posted by narual Quote
Not precisely. It depends on your settings.

Nikon calls it Active D-Lighting and Sony calls it DRO. I'm not sure if Pentax's highlight correction works the same way or not.
The company who owns the technology and licenses it calls it Adaptive Digital ISO:


But yeah, that's not the same as a grad filter. But since the possibility is there for it to adjust iso on a per pixel basis, maybe it could make one.

Wouldn't it be incredibly cool if the DSLR screen had a touchscreen, and you could swipe it with a finger and have it use edge detection to outline a digital grad filter nearly perfectly?
Thanks for the info about ISOAD, I had no idea it was a proprietary solution that Nikon uses ( and Pentax??)

But, yep, the swipe type idea is closer to what I have in mind, or maybe an in camera setting that would allow a selectable degree of falloff across the screen, in any chosen direction. Maybe it IS possible.
03-13-2015, 08:40 PM   #26
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Would you like to attempt a 'finger swipe' control for graduated ND (or any other blended effect) on a 3" LCD screen in the field in daylight? Or or do it during PP on a 15-22" monitor screen?

Digital filter effects have pretty well eliminated the need for optical filters excepting for POL or ND filters; and the ND filter is mostly useful for controlling shutter time vs. aperture ( 'bokeh'? ) rather than illumination - issues of ISO vs. noise notwithstanding. Digital grad ND effects are far more controllable and versatile than fixed optical filters.

If you haven't explored digital filter effects check out the on-line tutorials for Nik's Vivesa and Color Efex software. Search nik viveza tutorial .
03-15-2015, 02:31 AM   #27
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I think many camera have a 50 iso setting available.

As far as I understand, we use ND filter to allow for wider appertures and longer shutter times, sometime in combination with flash synchro speed.

The thing is even if iso25 was available, and there was not drawback at high iso, this would not be enough really for many case where an ND filter is required.

It is true that you could a long exposure of waterfull at sunset in a shadowed wood without filter. You could get maybe an f/4 or f/5.6 shoot in contra sunny day light.

But there would still needs for ND filters. Just take a look at the range of ND filters we have today: from ND2 to ND1000. ND1000 is 10 stops. Meaning counting you likely already use iso 100 or iso 50 on the camera that can, you would need iso 0.1 or 0.05 sensibility setting.

iso 25 is not going to cut it. And if that come with reduced high iso performance, then that an issue.
03-18-2015, 01:49 PM   #28
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Many thanks for all the wonderful replies to my question. Much more to it than I imagined (or come near to understanding, frankly).
03-21-2015, 07:28 AM   #29
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QuoteOriginally posted by Mistlefoot Quote
I'll ask the same question a different way....

Why is ISO 100 the lowest (highest?) ISO? ISO 50 would offer the same benefit as 1 stop. ISO 25, 2 stops.....
IIRC that's because the sensor has a base ISO, a native iSO. That may be 200, it may be 800, ... it can't get less sensitive than that. What the camera does at lower ISOs is take only a part of the dynamic range of the sensor and throw the rest away. If you go to ISO 25 you'd have a pretty low dynamic range.

For ND filters I don't think there is space in the camera.

They are useful for video though, cause often times you don't want the shutter speed to be too fast, as that leads to a stuttering effect.
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