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Why do many Nikons have such a low recommended ISO setting to optimize their Dynamic range?


Trippelforge

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I don't know if I explained my question right, but I have been scrolling through this website comparing various optimal ISO settings. The one thing I noticed is that most of the Nikon's listed have extremely low ISO suggestions (100-400). When I scan through the Canon list most are MUCH higher overall (800-1600). 

Can someone explain it to me? My thoughts on this subject are extremely basic. I always thought that ISO values increased the brightness of an image, and that there was a limit on how high of an ISO you could go until you were getting too much noise. So the goal was always to raise the ISO as high as you could before that point. According to the linked article my Nikon D5300 should only be set to ISO 200-400, and my Canon 500D at 1600. 

Hopefully what I am asking makes sense, as I would love a simple explanation as to what it actually means. I know currently if I drop my Canons ISO down to 800 I have to really crank up my exposure time. 

Thanks for the help!

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I'm new to AP so treat my words with caution, but my guess is it's to do with ISO invariance - according to this article (simply the first one that came up in a quick search) some Nikon's are ISO invariant whereas Canon's are not.

If nothing else I'm tempted to experiment and see what shooting with my D5500 at ISO 100 or 200 does for me 😁

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It depends on the sensor used where the ideal range of ISOs is. Sensors usually have a point where increasing ISO decreases full well capacity significantly but no longer reduces read noise as much. At that point its pointless to increase ISO as it will just saturate stars earlier but offer no benefit of significant value.

There is also this misconception that DSLR images should have a specific looking histogram or that the subs themselves should look good and show the target clearly. That is not necessary, the only thing deciding whether a sub is long enough is the amount of electrons in it, not the ADUs or histogram shape and placement. You get a brighter image by increasing ISO past the optimal point but it will still have more or less the same SNR as an exposure of the same length with one setting lower of an ISO.

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38 minutes ago, ONIKKINEN said:

It depends on the sensor used where the ideal range of ISOs is. Sensors usually have a point where increasing ISO decreases full well capacity significantly but no longer reduces read noise as much. At that point its pointless to increase ISO as it will just saturate stars earlier but offer no benefit of significant value.

There is also this misconception that DSLR images should have a specific looking histogram or that the subs themselves should look good and show the target clearly. That is not necessary, the only thing deciding whether a sub is long enough is the amount of electrons in it, not the ADUs or histogram shape and placement. You get a brighter image by increasing ISO past the optimal point but it will still have more or less the same SNR as an exposure of the same length with one setting lower of an ISO.

 

I haven't come across a well size for a DSLR before. Is it due to needing to look up the sensor itself? 

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14 minutes ago, Trippelforge said:

 

I haven't come across a well size for a DSLR before. Is it due to needing to look up the sensor itself? 

All sensors have a maximum capacity of electrons a single pixel can hold, once that limit is reached the pixel is saturated to full white and all further information to that pixel is lost. Increasing ISO will lower full well capacity and read noise. There is a point in which read noise no longer decreases significantly but FWC does, before that point is the right place for the ISO to be (the tables seem to make sense here and yours should probably be used in the recommended range).

Dynamic range is the difference between read noise and FWC by the way. But dynamic range of a single exposure is not very important in AP as we stack hundreds of exposures to increase the effective dynamic range so the 1 sub dynamic range is mostly a pointless stat.

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3 hours ago, imakebeer said:

I'm new to AP so treat my words with caution, but my guess is it's to do with ISO invariance - according to this article (simply the first one that came up in a quick search) some Nikon's are ISO invariant whereas Canon's are not.

If nothing else I'm tempted to experiment and see what shooting with my D5500 at ISO 100 or 200 does for me 😁

Apart from the Canon 80D, drives me mad having to shoot at ISO 100-200 all the time 😀

Alan

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I have a Nikon D5100 and regularly shoot at 1600 iso. Just use lots of dithered subs. I also have an 800E and shoot that at 1250 iso as that seems it's sweet spot (iso wise).

Edited by fwm891
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My D5600 gives much better colour in DSO imaging at ISO 200 to 400. It provides more dynamic range and is ISO invariant. You have to nail the exposure duration as the jpeg preview and histogram are hard up to the left

Whatever the ISO, the sensor captures a fixed amount of photons for a given aperture and exposure.  The optimum ISO depends on the downstream electronics, read noise, and thermal noise

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