Need help with exposure question

[AlanKlein]

I have no delusions that I'm going to banish stupid from Youtube or escort the ET out behind the barn from whence it will not return. I know what most photographers think they mean when they say "exposure." I however have the official responsibility to be guardian of the truth. I get a paycheck for it. And contrary to what Alan claims understanding the distinction here and knowing how these things actually work does translate into the real world of taking photos.

Joe

Joe, Below is the link for my photos. Where is yours?

 

[Ysarex]

@Ysarex

ack, I was looking at upgrading my gear the past few weeks (which is how I found this forum) and I decided against it for now. The reality, for the pictures I take now (landscape, vacations stuff, family, friends....) my Sigma lenses and Canon 6D are "good enough" (ok, my older kit lenses suck), and I was planning to wait till some point next year when the mirrorless market might start to shake out a bit.

Then I read about the invariant ISO sensors, and look at the image from the Fuji....


Tim

There's a whole new crop of amazing sensors coming on line right now and primarily showing up in Nikon, Fuji and Sony gear. Watch Bill Claff's data. Look at this graph for the new Nikon D500:

Photographic Dynamic Range versus ISO Setting

See that break (dog leg) in the graph at ISO 400. You want to watch for that sensor. Here it is again in the graph that indicates ISO invariance:

Shadow Improvement of Photographic Dynamic Range versus ISO Setting

The straighter that line the more ISO invariant the sensor.

That dog leg is a new feature that Sony bought from Aptina. The sensor is dual impedance. The best way to think of it is it's two sensors in one. At base ISO up to the dog leg channel A is read then at all ISOs above the dog leg channel B is read. In my Fuji the dog leg is at ISO 800. Fuji sets the base ISO at 200 while Nikon sets it at 100.

So to use my Fuji I do have to switch between at least ISO 200 and 800. The second impedance channel is optimized for the higher ISOs and I'm going to tell you I can shoot this camera at ISO 12,800 and you'd be amazed what I can get from it (see below). Now just to make the point I can get the same result as long as I got the ISO above the dog leg.

Joe

 

[n614cd]

Joe, Below is the link for my photos. Where is yours?

Did you mess up the quotes? Are you talking to @Ysarex or me?
I do not have a public page hosting my images anymore.

Tim

 

[Ysarex]

Oh by all means lets visit the real world. I was asked (friends) to take some photos at an event (no flash please just blend in quietly). Here's one of those real world photos:

View attachment 165179

That's the JPEG my camera created. I left the ISO at base (200) and to get a fast enough shutter speed for hand-holding I used the EC adjustment on the camera (Fuji XE-2) and set it to -1.67 (EXIF data is in the photo if you want to check). Now be honest; would you have raised the ISO until you had a better "proper exposure" of the gentlemen at the table?

Joe

Without knowing the aperture and shutter settings, I would have no way of answering your question intelligently.

They're in the EXIF data that's why I mentioned it. 1/140 sec shutter speed f/5.6 using a zoom lens that would be wide open here at f/4 and not a good idea to use at f/4.

Joe

 

[AlanKlein]

Joe, Below is the link for my photos. Where is yours?

Did you mess up the quotes? Are you talking to @Ysarex or me?
I do not have a public page hosting my images anymore.

Tim

How could I assess your knowledge if you don't show me what you got? It's easy to talk a good game. Where's the practical proof you know what you;re talking about?

 

[AlanKlein]

Oh by all means lets visit the real world. I was asked (friends) to take some photos at an event (no flash please just blend in quietly). Here's one of those real world photos:

View attachment 165179

That's the JPEG my camera created. I left the ISO at base (200) and to get a fast enough shutter speed for hand-holding I used the EC adjustment on the camera (Fuji XE-2) and set it to -1.67 (EXIF data is in the photo if you want to check). Now be honest; would you have raised the ISO until you had a better "proper exposure" of the gentlemen at the table?

Joe

Without knowing the aperture and shutter settings, I would have no way of answering your question intelligently.

They're in the EXIF data that's why I mentioned it. 1/140 sec shutter speed f/5.6 using a zoom lens that would be wide open here at f/4 and not a good idea to use at f/4.

Joe

You could lower the EC another stop or so. Maybe it would be better to slow the shutter by one stop or raise the ISO one stop. You could also use the RAW image that would give you more play with the shadow slider. A lot depends on the capability of your camera's DR.

 

[n614cd]

How could I assess your knowledge if you don't show me what you got? It's easy to talk a good game. Where's the practical proof you know what you;re talking about?

Alan,

Hmmm, how to put this since TPF seems like a family forum....
I give up, I do not have a polite way to say it....

I did follow your debate with Joe (@Ysarex ). I could not follow your point(s). As I told him...
As for determining if I know what I am talking about by looking at my images?
Nothing in this discussion deals with my artistic ability (and the definite lack there of) or my ability to apply the knowledge.

Tim

 

[AlanKlein]

If flash is not an option, you could have added more ambient light, possibly the best solution.

 

[n614cd]

There's a whole new crop of amazing sensors coming on line right now and primarily showing up in Nikon, Fuji and Sony gear. Watch Bill Claff's data. Look at this graph for the new Nikon D500:

Photographic Dynamic Range versus ISO Setting

See that break (dog leg) in the graph at ISO 400. You want to watch for that sensor. Here it is again in the graph that indicates ISO invariance:

Shadow Improvement of Photographic Dynamic Range versus ISO Setting

The straighter that line the more ISO invariant the sensor.

Pages bookmarked, I have seen them referenced before but have not dug into them. I guess I have some reading to do....

Tim

 

[AlanKlein]

Alan,

Hmmm, how to put this since TPF seems like a family forum....
I give up, I do not have a polite way to say it....

I did follow your debate with Joe (@Ysarex ). I could not follow your point(s). As I told him...
As for determining if I know what I am talking about by looking at my images?
Nothing in this discussion deals with my artistic ability (and the definite lack there of) or my ability to apply the knowledge.

Tim

Thanks for your honesty.

 

[Ysarex]

You could lower the EC another stop or so. Maybe it would be better to slow the shutter by one stop or raise the ISO one stop. You could also use the RAW image that would give you more play with the shadow slider. A lot depends on the capability of your camera's DR.

If flash is not an option, you could have added more ambient light, possibly the best solution.

That wasn't possible -- all the interior lights were on. I wasn't comfortable with a slower shutter speed. And in that situation you would have raised the camera ISO. That's your exposure triangle methodology. And in the real world raising the ISO would have reduced DR -- that's what it does. You would have ISO clipped the information out the window with the DR reduction that came from raising the ISO.

So here's a real world example of how applying an understanding of the way the camera works allowed me to take a photo that you would have failed to get if you raised the ISO.

Because I didn't raise the ISO I retained the full DR of the sensor and I was able to keep the real world data that you see out the window in my finished photo. And that's a real world example of how you can take a better photo when you understand how the hardware works and can think clearly about it. I got a real world better photo by ignoring the triangle.

Joe

 

[n614cd]

You could lower the EC another stop or so. Maybe it would be better to slow the shutter by one stop or raise the ISO one stop. You could also use the RAW image that would give you more play with the shadow slider. A lot depends on the capability of your camera's DR.

If flash is not an option, you could have added more ambient light, possibly the best solution.

That wasn't possible -- all the interior lights were on. I wasn't comfortable with a slower shutter speed. And in that situation you would have raised the camera ISO. That's your exposure triangle methodology. And in the real world raising the ISO would have reduced DR -- that's what it does. You would have ISO clipped the information out the window with the DR reduction that came from raising the ISO.

So here's a real world example of how applying an understanding of the way the camera works allowed me to take a photo that you would have failed to get if you raised the ISO.

View attachment 165183

Because I didn't raise the ISO I retained the full DR of the sensor and I was able to keep the real world data that you see out the window in my finished photo. And that's a real world example of how you can take a better photo when you understand how the hardware works and can think clearly about it. I got a real world better photo by ignoring the triangle.

Joe

Joe,

This now prompted a thought. I know there is the whole concept of expose to right. As in better to be overexposed by a stop than underexposed.
How does ISO come into play, or does it not?

Tim

Sent from my SM-J737T using Tapatalk

 

[AlanKlein]

Good example Joe. But what do you do with a scene where you don't have the lighter background but just the same lighting throughout? Do you raise the iso? Or, do you keep the iso lower and then adjust the exposure higher in post processing? How do you know which is better, do these examples also depend upon the make of the camera? How do you explain to users of any piece of a camera which is the best way to go?

 

[Ysarex]

Good example Joe. But what do you do with a scene where you don't have the lighter background but just the same lighting throughout? Do you raise the iso?

Normally yes, raise the ISO. It's good to raise the ISO if you need it, just don't clip diffuse highlights. When you raise the ISO you lose dynamic range. Look at this graph:

Photographic Dynamic Range versus ISO Setting

A Nikon D5600 delivers 10 and 1/2 stops of DR at ISO 100. At ISO 3200 half of that is gone. If you have a high DR scene, losing half the sensor's DR capacity can be a show stopper. With low DR scenes there is no penalty to raising the ISO. The Exposure Triangle doesn't talk about ISO and DR. It talks about ISO and noise and ISO doesn't cause noise, but it sure chops off your DR.

Here's another more extreme example that I set up. First look at this camera JPEG:

(For the sake of the illustration we can't fix the lighting and the subject of the photo is the ornamental chair you can't see right now next to the bookcase.) I have the raw file that created that camera JPEG and I set the exposure so that the highlights out the window would be at sensor saturation at base ISO on the camera (125). I took two photos:

I raised the ISO to an appropriate level to get a decent JPEG of the chair using the same exposure that I had calculated at ISO 125 -- photo on left. OK, so nearly 5 stops of ISO increase whacked off about 5 stops of my sensor DR (comes off the top) and even though I processed the raw file the highlights in the curtains and out the window are nuked to h*ll. That's ISO clipping and it clips DR from the top. On the right you see the result of processing the raw file that produced that camera JPEG above. Without ISO clipping I had all the data the sensor could record.

And here's the big critical bottom line: They're both the same exposure, 1/8 sec at f/6.3. The exposure and only the exposure determines the data the sensor records if (BIG IF) the sensor is ISO invariant. Coming in after the exposure, a raised ISO takes data off the top but if there's no penalty for leaving the ISO at base with an ISO invariant sensor I can have all the data.

Some of the advances we're seeing are in fact breathtaking. I think what we're looking at above is breathtaking. I could never have done that with Tim's Canon 6D or my old 5Dmkii and here I am pulling it off with a $500.00 pocket compact ten years later. The sensors in Canon's older DSLR were very much NOT ISO invariant. They relied on the analog gain to help retain image data on the low end that would otherwise swamp out in read noise.

That image above represents a new capability that our newer cameras are making available. We couldn't do that in the past. ISO invariance is becoming normal. When I bought the G7 used to take the photos above I didn't care that it was ISO invariant. I was surprised when I tested it to find out. I'm happy to use the ISO and typically I do, I raise it as needed. But I also know what the camera is capable of.

So real world: I'm out working in the garden with my wife. I always have the G7 with me. It's evening just as the sun is setting and she says, "hey I want to send a picture to my sister, can you take one from here that shows the yellow zinnias." The sun is setting in a hazy sky and the photo she wants has me looking right at that sunset. I was able to move to get it behind the tree but this is backlight. We all know what happens when we shoot a sunset; the foreground goes silhouette. If she had asked me for a close up of the zinnias I would have raised the ISO, but she wanted the whole garden. So I kept the ISO at base and calculated the exposure to put the sky at sensor saturation. Here's that photo with it's camera JPEG above it.

Very high DR, I can do it if I want.

Or, do you keep the iso lower and then adjust the exposure higher in post processing? How do you know which is better, do these examples also depend upon the make of the camera? How do you explain to users of any piece of a camera which is the best way to go?

It really does depend on the hardware -- ISO invariance is new for us and it's required to pull this off. It also depends on what you're willing to do in the way of post processing. I'm accustomed to only shooting raw and processing all my photos. Not everyone is and legitimately so. ISO makes camera JPEGs possible and for many people that's critical. If I went to chimp that garden shot above I'm going to look at that JPEG on the LCD and say, "looks good?" It looks horrible! It's all green and underexposed except for the sky which is overexposed. Most people expect to click the shutter and immediately see a decent looking photo. They have to use the ISO function in the camera to do that and they should. I do that too most of the time.

The point in all this that matters for me is that, because I have a proper understanding of how it all works, when my wife asks me to take an impossible photo to send to her sister I can change gears and say, sure -- no problem. Not realizing any other option existed, most people would have taken that garden shot and nuked the sky to h*ll. I didn't have to.

Joe

 

[zulu42]

That is a great example Joe posted. These discussions have led me to investigate the ISO invariance of the sensor in my D800. Searches led me to this article:
ISO Invariance Explained - Photography Life
which linked me to this page:
Input-referred Read Noise versus ISO Setting

My own real-world example I'm working in my head is a starry sky shot. I like to open the lens all the way and take 30 second exposures - soaking the sensor with as much starlight as possible. So, looking at the chart for my D800, which I almost understand, I'm thinking I should use ISO 1600 which is the highest actual ISO value before "simulated" ISO value... or is it 6400? Or do I just use base ISO of 100?