Digital Photography ISO

Nothing mysterious here, in the old days you controlled the shutter speed and aperture and loaded your camera with the film speed (ISO) you thought you would need. Maybe you could push it or pull it in the darkroom a bit.

With digital you still control the shutter speed, aperture and now you can also change the film speed between shots.

You still have the same issues however. the faster you push the ISO the "grainer", it called noise these days, the picture.

Well Grandpa, some help here then as I seem to have a mystery on my hands. According to you faster (higher) ISO values are going to make my photo "grainier" -- noisy. But that doesn't seem to be happening. I just took these two photos:

compare.jpg


One at ISO 125 and the other at ISO 1600 and the higher ISO photo doesn't look any noisier than the lower ISO photo. In fact if anything the higher ISO photo is maybe a smidge less noisy. What's the deal?

Here's both photos at full res so you can pixel peep them:

ISO 125
ISO 1600

They were both processed with luminous noise filtering turned off so as not to interfere. Why isn't the ISO 1600 photo noisier than the ISO 125 photo?

Joe

As always, good photography requires knowledge of all the effects of the camera's variables. With digital you have many more right at your fingertips.
 
Yogi Bear might have something to say in this thread, should he appear. I miss seeing Yogi. The last time I saw him was back in the ASA 64 Kodachrome era.
 
Yogi Bear might have something to say in this thread, should he appear. I miss seeing Yogi. The last time I saw him was back in the ASA 64 Kodachrome era.

yogi-bear-camera-vintage-1970s.jpg
 
Ysarex in fairness for your test you've kind of got to mention the camera you are using now since its not just a case of exposure methods (eg expose to the right) helping to keep noise down; but also because some brands (eg Nikon and Sony) now have sensors which have tiny amounts of noise even if you recover from underexposure; whilst Canon and some other brands are still using sensors that require correct exposure otherwise any brightening can result in increased noise.
 
Without getting technical, it's my understanding that my K1MII has several thousand tiny little maintenance workers with brooms that run all over the sensor sweeping up the excess noise whenever I go into the mega ISO stage. :biggrin-93:
 
Ysarex in fairness for your test you've kind of got to mention the camera you are using now since its not just a case of exposure methods (eg expose to the right) helping to keep noise down; but also because some brands (eg Nikon and Sony) now have sensors which have tiny amounts of noise even if you recover from underexposure; whilst Canon and some other brands are still using sensors that require correct exposure otherwise any brightening can result in increased noise.

It's all in the EXIF data but sure; Canon G7xii.

Joe

P.S. The move toward ISO invariant sensors is well underway. That Canon G7 I'm using is functionally ISO invariant and you mentioned Canon specifically as a make that in years past was not. And so considering that, what you're acknowledging is what that illustration shows: the source of the noise isn't something that ISO is doing in the camera. In fact quite the opposite; what ISO does internally in the camera elctronics either suppresses noise or is noise neutral. Just trying to help Grandpa Ron get cause and effect straight in this case.
 
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Yeah I'm not surprised Canon is moving in the same direction with the technology - they could hardly not otherwise Nikon and the others would leave them in the dust. The ISO invariant tech is probably going to be one of the biggest (if also oddly quite quietly released) events in the camera world since almost removing the pressure of proper exposure vastly increases creative possibilities for many photographers.


I will be interested in seeing what comes next year from Canon - they've a few lines that are ripe for an update with newer age sensors!
 
Yeah I'm not surprised Canon is moving in the same direction with the technology - they could hardly not otherwise Nikon and the others would leave them in the dust. The ISO invariant tech is probably going to be one of the biggest (if also oddly quite quietly released) events in the camera world since almost removing the pressure of proper exposure vastly increases creative possibilities for many photographers.

It's oddly quiet because all of the camera manufacturers are focused on their camera's JPEG output in which case ISO invariance is irrelevant.

You can think about it as removing pressure for proper exposure but that makes me cringe so I'm going to prefer to think about it as expanding the possibilities for creativity. That's why a correct understanding of what's happening under the hood can matter. I regularly take photos that people who are stuck thinking digital ISO is just like film can't take at all.

Consider this difference between film/ISO and digital/ISO: As you raise film ISO you also typically increase DR capacity -- faster films have an increased ability to record a larger dynamic range. Digital/ISO is the exact opposite. As you increase ISO on a digital camera you're chopping off DR. Nobody seems to learn that. It's not on the exposure triangle -- just ISO = noise (and it doesn't). Now let's put that fact and ISO invariance together and see what happens with a high DR scene. I grabbed a couple baskets and stuck them in front of the window. Again the Canon G7:

dr_compare.jpg


I didn't bother to match the color because what's of concern here is the highlights. I set the camera to expose for the baskets at ISO 3200 and got an exposure of 1/30th sec at f/8. The highlights in the curtain and out the window are nuked in the raw file -- unrecoverable. So I kept the same exposure but dropped the ISO to 125. At ISO 3200 the G7 has a DR capacity of 4.5 stops. At ISO 125 it's DR capacity is 9 stops. That's double! In the photo on the left I used the 9 stops and kept the detail in the curtain but in the photo on the right I didn't have 9 stops. In the ISO 125 camera JPEG there is no bookcase and decorative chair -- just solid black. But at the same exposure it's recorded just as well as it is in the ISO 3200 photo. To keep the highlights in the ISO 3200 photo I'd have to reduce the exposure which is the last thing I want to do for the basket and the room interior -- basically not possible with only 4.5 stops of DR.

Knowing how the machine works lets you use it to full advantage.

Joe

I will be interested in seeing what comes next year from Canon - they've a few lines that are ripe for an update with newer age sensors!
 
This is something I have been struggling with, and after reading this article, I'm still struggling. I "grew up" in film and I understand film ISO. I also understand the basics of electronic sensors. So I should see a digital ISO and know what it is telling me, right? Well, I really don't. I just use it like I was using a film camera as best as I can.

"You probably don't know what ISO means – and that's a problem" Published Aug 6, 2018 | Richard Butler
Hi you grew up with iso I grew up with ASA lol and yes I do the same as you and I tend to play with the camera and the ISO /appature/shutter speed settings to see what changes
 

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