"Automagic" ISO setting on a DSLR

[taylorkh]

In the old film days I would select my film based on ISO. Perhaps 100 or 200 when I wanted detail - low graininess, 400 for general snapshot sort of pictures and a 800 or higher if I needed to shoot in low light or fast moving subjects. I set the film's ISO on the camera and usually shot in aperture priority mode. With my new D3400 I also tend towards aperture priority and allow the meter to set the shutter speed.

However, on the DSLR I observe that the ISO fluctuates wildly. 100 to 26,500! With film, the ISO represented the sensitivity of the film to light. Higher ISO, more sensitive but larger grains. This was a physical characteristic of the emulsion on the film. I am trying to understand what the ISO means on a DSLR? Obviously I am not changing the number of pixels on the sensor (I don't think). I am looking to learn and get my head around this.

And should I lock down the ISO rather than let it run wild?

TIA,

Ken

 

[Texas]

You are on "iso auto". Turn it off, then pretend you are back in the film days.

Pick and lock in an iso value that you want.

 

[Don Kuykendall_RIP]

And should I lock down the ISO rather than let it run wild?

TIA,

Ken

Auto ISO can be a great tool. You do not say which camera you are shooting since it is not in your profile. You can limit the range of your ISO in Auto. Depending on what I am shooting I set mine to a max of 1200. With my D750 that is still a good look.

 

[taylorkh]

Thanks folks,

The camera is a D3400 - and I was a little dyslexic when typing the max - should have been 25,600 not 26,500 - not that it really matters.

I have been doing some digging in the manual and poking around the menus. I found this statement

(choose lower values to prevent noise (randomly-spaced bright pixels, fog, or lines)

OK but I still cannot relate that to film characteristics.

I also learned a bit about how the auto ISO will vary the ISO if the value I chose (currently 400) will not provide the optimal exposure. I also learned that I can set a maximum auto ISO - just set this to 1600.

With these settings and auto ISO turned on I THINK that the ISO can vary from 100 to 1600 in P, S, or A mode. The manual says M mode as well. I thought that M meant MANUAL EVERYTHING but I guess not.

However, I have not figured out if setting the default ISO value serves any purpose when the camera is in auto ISO mode and will vary the ISO to its liking.

This section of the manual is not very clear.

Thanks again,

Ken

 

[Don Kuykendall_RIP]

The M mode is one of the great things about Auto ISO. I use that when I am shooting birds in flight. I want f8 @ 1/1600 sec so I set that and let Auto ISO give me the correct exposure.


Sent from my iPhone using Tapatalk

 

[Needa]

I have been doing some digging in the manual and poking around the menus. I found this statement OK but I still cannot relate that to film characteristics.

Ken

It isn't the same as film. ISO in a digital camera is an amplification circuit. The sensitivity of the chip does not change. The signal coming from the chip gets get increased. When this happens the noise is also increased. It is similar to film in that by increasing the setting it will allow you to increase the exposure or keep a higher shutter speed or a smaller aperture opening (higher F number) while maintaining the same exposure

 

[BackdoorArts]

The M mode is one of the great things about Auto ISO. I use that when I am shooting birds in flight. I want f8 @ 1/1600 sec so I set that and let Auto ISO give me the correct exposure.


Sent from my iPhone using Tapatalk

This exactly. Though I use Auto ISO in Aperture Priority all the time as well.

ISO in the digital realm is a measure of amplification of light information after the sensor processes it. All current Nikon models have a "Native ISO" of 100, meaning that what you get at ISO 100 is pure from the sensor with no amplification. If you think about amplification in musical terms native ISO is where a guitar amplifier is delivering full, pure tone from the instrument with no distortion (i.e. "noise") of the signal. As you increase the volume (i.e. go to higher ISO values) from that point the signal will begin to distort (i.e. get noisier). How much depends on the amp/camera. Some begin to distort quickly, others may take some time, but at some point they'll all get noisy. I've found most current sensors to be really good through about 6400 depending on the amount of detail in the frame. My first Nikon, a D7000, couldn't go past 1600. My D750 can do 6400 easy. My D500 can get there as well, but for birds I don't like anything above 4000 and prefer to keep it at 3200. I should add that many cameras allow you to go below 100 which is attenuation instead of amplification. Again as with an amplifier you will lose something when you do it, the question is whether you even notice it and whether it can be dealt with in post.

Speaking of which, all this assumes you're shooting RAW, which you should. All the time.

With each camera I have I decide what the maximum acceptable ISO setting is for whatever situation I'm in and then I program the Auto ISO settings so that they do not exceed that while also capping the shutter speed in a way that guarantees I don't accidentally blur the photo by moving while shooting in Aperture. That leaves me to concentrate on the shot instead of the camera.

Does that make me less of a photographer? Don't know, don't care. Are Formula One drivers today lesser drivers than those who pioneered the sport with lesser cars and manual everything? Are golfers today less talented than Jack and Arnie because they have more forgiving equipment? Honestly, who cares.

I think anything that allows an artist of any type to concentrate on the result instead of the tools used to create it is a good thing. Sure using a DSLR is easier, but so is just about anything these days. For film photographers I can see how features like this can make you think less of the skill of the photographers using it, but for me it's all about a tradesman with a tool thing - when you're given a tool you learn how to use it to its fullest.

 

[hark]

Though I use Auto ISO in Aperture Priority all the time as well.

I rarely use Auto ISO only because I was a staunch 35mm film lover. In fact, I can't even wrap my head around how Auto ISO would work in Aperture Priority since the body changes the shutter value to compensate for a correct exposure. I know what I'm gonna look up online. Thanks for your detailed explanation.

 

[pforsell]

With film, the ISO represented the sensitivity of the film to light. Higher ISO, more sensitive but larger grains. This was a physical characteristic of the emulsion on the film.

To be more exact, the ISO of films represent the combination of the emulsion + the developing. Some companies sell/sold the exactly same film emulsion with different speed ratings (Ilford, for one), where the only difference was the recommended developing. (I'm not talking about push/pull processing, but the actual ratings printed on the film box.) One might think the camera ISO as being part of the developing - just like it is with films - and in this sense the digital and analog ISO speeds differ very little.

And should I lock down the ISO rather than let it run wild?

There's situations where one scenario is better than the other. In a wildly changing lighting Auto ISO might be useful. In constant lighting perhaps manual setting is better - I trust my own judgement better than the camera's.

In any case, I think that ISO last is the preferred approach. First determine your DOF requirements and action stopping requirements, and set aperture and shutter speed accordingly. If this leads to low exposure, then adjust ISO upwards as much as you can while taking care to not clip any important highlights in the image. This approach goes by the name ETTR, expose to the right, where the "right" refers to the histogram display of your camera.

 

[taylorkh]

Thank you all for the great information! This is starting to make sense.

As to Jake's comment about Formula 1... F1 is something which does NOT make sense. Given a clean sheet of paper and the rules that the car must have 4 wheels and a driver... any competent F1 designer could easily produce a car which a human being could not drive on the track. Too fast for human reflexes and generating so much G force in braking and cornering that the driver would loose consciousness. To alleviate this the sport has incredibly complex rules which result in very overpriced cars which the lower tier constructors cannot afford and which cannot get close enough to the car they are chasing for any real racing. The results are by and large boring!

So, even though active aerodynamics are banned, DRS was added back. Ground effect skirts are banned so we have wings which are so complex (and ugly) they only work in clean air. The "steering wheel" is a computer console and the driver has to worry about conserving tires. Rubbish. Refueling was banned (for politically correct reasons I guess) but it was a great source of entertainment. The last year of refueling (2010 I thnk?) Ferrari had a remote control "lollipop" to release the driver from the pits. It was controlled by someone in Marinallo I guess. But the remote person really did not have a good handle on things in pit lane. They would routinely send out the car with the fuel can attached, the fuel man attached, run over another team's fuel man etc. Exciting!

Off my soapbox now And thanks again for the great information on DSLR ISO.

Ken

 

[Chucktin]

I always think of (electronic) noise in a DSLR as the equivalent of fog in a film emulsion's "base+fog" dynamic.

The more we push-processed, or the longer we stored a specific brick of still film, the higher the base+fog we observed.

Really noise is a good indicator of Image Quality because it is a resultant of the internal circuitry attached to a sensor chip.

As the cameras matured the noise decreased due to better manufacturing and better design choices by Nikon/Canon/Sony/Fuji, etc. However those decisions cost $ that some manufacturers choose to forgo.

 

[taylorkh]

ThanksChucktin,

I recall some folk saying in the old days that you had to store color film for a certain number of months before it was at its best.

Speaking of fog... there is the classic case of Kodak's fogged sheet film back in the late '50s or early '60s. The Kepner-Tregoe problem solving methodology used that as one of their case studies. I recall taking a K-T course MANY years ago. The instructor described the symptoms - Kodak was receiving complaints about high end sheet film being fogged right out of the package. We the students were supposed to apply the K-T process to solve the problem.

As it turns out there was a chemist and rather remarkable character in the class. He said before we even started "I bet it's the separator paper between the sheets." This of course WAS the cause - residue from some chemical used in bleaching the paper interacted with the film. Blew that example/exercise out of the water. Turns out the chemist was an avid photographer and had been involved in investigating the Kodak paper fiasco.

Ken

 

[Chucktin]

Yes, I have heard both stories. But by that time we were 80/90 percent roll film. The biggest row was the 35mm fans vs the 120 fans with the sheet filmers making up the rest.
Auto ISO is a useful adjunct but I keep mine manually set as low as I can to maximize image quality.

 

[Texas]

I remember when the open air nuke testing in Nevada caused some serious fog problems at the Kodak film factory in NY state.

 

[hark]

This exactly. Though I use Auto ISO in Aperture Priority all the time as well.

ISO in the digital realm is a measure of amplification of light information after the sensor processes it. All current Nikon models have a "Native ISO" of 100, meaning that what you get at ISO 100 is pure from the sensor with no amplification. If you think about amplification in musical terms native ISO is where a guitar amplifier is delivering full, pure tone from the instrument with no distortion (i.e. "noise") of the signal. As you increase the volume (i.e. go to higher ISO values) from that point the signal will begin to distort (i.e. get noisier). How much depends on the amp/camera. Some begin to distort quickly, others may take some time, but at some point they'll all get noisy. I've found most current sensors to be really good through about 6400 depending on the amount of detail in the frame. My first Nikon, a D7000, couldn't go past 1600. My D750 can do 6400 easy. My D500 can get there as well, but for birds I don't like anything above 4000 and prefer to keep it at 3200. I should add that many cameras allow you to go below 100 which is attenuation instead of amplification. Again as with an amplifier you will lose something when you do it, the question is whether you even notice it and whether it can be dealt with in post.

Speaking of which, all this assumes you're shooting RAW, which you should. All the time.

With each camera I have I decide what the maximum acceptable ISO setting is for whatever situation I'm in and then I program the Auto ISO settings so that they do not exceed that while also capping the shutter speed in a way that guarantees I don't accidentally blur the photo by moving while shooting in Aperture. That leaves me to concentrate on the shot instead of the camera.

Does that make me less of a photographer? Don't know, don't care. Are Formula One drivers today lesser drivers than those who pioneered the sport with lesser cars and manual everything? Are golfers today less talented than Jack and Arnie because they have more forgiving equipment? Honestly, who cares.

I think anything that allows an artist of any type to concentrate on the result instead of the tools used to create it is a good thing. Sure using a DSLR is easier, but so is just about anything these days. For film photographers I can see how features like this can make you think less of the skill of the photographers using it, but for me it's all about a tradesman with a tool thing - when you're given a tool you learn how to use it to its fullest.

I realize this is a somewhat old post but have reached the point where I need to use Auto ISO. I just don't understand Jake's comment about using Auto ISO while in Aperture Priority mode. I know how to set it in Manual Mode. How does the shutter get controlled if the camera is using Auto ISO in Aperture Priority?

I keep U1 programmed for BBF in Aperture Priority with a set value for my aperture and my ISO (wasn't using Auto ISO). When I needed it yesterday, I missed the shot since my shutter was too slow (around 1/400" for BIF). U2 is programmed for BBF in Manual Mode. I want to set up both of these to incorporate Auto ISO. I can do the Manual Mode one. But how to I determine my shutter speed while in Aperture Priority? Does anyone know?

 

[hark]

I realize this is a somewhat old post but have reached the point where I need to use Auto ISO. I just don't understand Jake's comment about using Auto ISO while in Aperture Priority mode. I know how to set it in Manual Mode. How does the shutter get controlled if the camera is using Auto ISO in Aperture Priority?

I keep U1 programmed for BBF in Aperture Priority with a set value for my aperture and my ISO (wasn't using Auto ISO). When I needed it yesterday, I missed the shot since my shutter was too slow (around 1/400" for BIF). U2 is programmed for BBF in Manual Mode. I want to set up both of these to incorporate Auto ISO. I can do the Manual Mode one. But how to I determine my shutter speed while in Aperture Priority? Does anyone know?

I did some digging and figured out the settings for Auto ISO in Aperture Priority while setting a minimum shutter speed value. Those settings are saved as U1 and U2. What I don't understand now is why I cannot set Aperture Priority for Auto ISO while Manual Mode is a straight ISO value. If it's set as Auto ISO while in Aperture Priority, it stays in Auto ISO for Manual Mode. Oh well. I turned Auto ISO off for those and only have it set for U1 and U2. That will be fast to change the settings.

 

[Horoscope Fish]

I realize this is a somewhat old post but have reached the point where I need to use Auto ISO. I just don't understand Jake's comment about using Auto ISO while in Aperture Priority mode. I know how to set it in Manual Mode. How does the shutter get controlled if the camera is using Auto ISO in Aperture Priority?

I keep U1 programmed for BBF in Aperture Priority with a set value for my aperture and my ISO (wasn't using Auto ISO). When I needed it yesterday, I missed the shot since my shutter was too slow (around 1/400" for BIF). U2 is programmed for BBF in Manual Mode. I want to set up both of these to incorporate Auto ISO. I can do the Manual Mode one. But how to I determine my shutter speed while in Aperture Priority? Does anyone know?

It gets complicated. You might find this article helpful... Skip down to section 5.1) Aperture Priority with Auto ISO :: What is Auto-ISO

 

[hark]

It gets complicated. You might find this article helpful... Skip down to section 5.1) Aperture Priority with Auto ISO :: What is Auto-ISO

Thanks for this info, Paul. It's interesting as well as informative. I forget about that web site--he supplies excellent information.

I have U1 set for Aperture Priority with Auto ISO and U2 for Manual Mode with Auto ISO. Most likely the latter is the one I will now use. I'm accustomed to working in Manual Mode although not with Auto ISO. It should work well for my shooting style since it's SUPER easy to change aperture AND shutter speed on the fly.

The thing that annoys me is how the Nikon DSLR bodies are set up for changing the ISO. There is a button on the rear that gets pushed along with scrolling the rear wheel. BUT if the image display has not yet turned off, you cannot change the ISO. The rear display simply changes from showing 1 image to showing multiple images. And that's exactly what happened yesterday. As soon as I went to change the ISO, the image display split the screen into multiple images. And I knew I lost my chance at getting a decent shot with better settings.

 

[Michael J.]

I realize this is a somewhat old post but have reached the point where I need to use Auto ISO. I just don't understand Jake's comment about using Auto ISO while in Aperture Priority mode. I know how to set it in Manual Mode. How does the shutter get controlled if the camera is using Auto ISO in Aperture Priority?

I keep U1 programmed for BBF in Aperture Priority with a set value for my aperture and my ISO (wasn't using Auto ISO). When I needed it yesterday, I missed the shot since my shutter was too slow (around 1/400" for BIF). U2 is programmed for BBF in Manual Mode. I want to set up both of these to incorporate Auto ISO. I can do the Manual Mode one. But how to I determine my shutter speed while in Aperture Priority? Does anyone know?

I followed this steps and it works great

 

[hark]

I followed this steps and it works great

Thanks for this, M.J.! That had 2 things in it I hadn't known. [MENTION=13090]Horoscope Fish[/MENTION] - did you know about either of these?

1. With some bodies, there is/was a glitch when setting Auto ISO. Near the end of the video, he went in and turned off Auto ISO, lowered his ISO to 100, then went back in and set Auto ISO. Coincidentally mine was set for ISO 1600 like his, and when I went into the rear screen, it displayed as ISO 1600 even though it should have gone lower.

2. While in Aperture Priority with Auto ISO, he shows an alternative to using the +/- button for exposure compensation. That can be changed to raise/lower with the rear wheel instead of the 2-handed method.

Thanks again, Michael. Good to know this.