amfoto1 Loc: San Jose, Calif. USA

Sorry, but I completely disagree with you.



That's incorrect.

"Real" M (manual) mode means the photographer is setting all three of the exposure parameters themselves: Shutter speed, lens aperture and sensitivity to light (ISO). The camera isn't making any of the settings automatically.

Once Auto ISO is enabled along with M mode, it's no longer manual. Based upon it's meter reading, the camera is "automatically" choosing one of those exposure parameters... ISO.

As a result M with Auto ISO (only possible with digital) is is simply another AE mode, same as:

- Tv or S "Shutter Priority AE" where the photographer sets ISO and shutter speed, but the camera selects the aperture it "thinks" will make a correct exposure.

- Av or A "Aperture Priority AE", where the photographer selects ISO and aperture, while allowing the camera to set a shutter speed it thinks will make a correct exposure.

- and P "Program AE", where the photographer sets the ISO and camera chooses a combination of aperture and shutter speed it hopes will make a correct exposure.

One reason it's important to make the distinction between truly manual exposure and an AE mode is Exposure Compensation, which is a feature that's provided on many camera for use with AE. Granted, not everyone uses it, but E.C. serves to tweak the AE mode for more accurate exposure than the camera can achieve on its own (due to the limitations of reflective metering, which is strongly influenced by subject tonality). There's no E.C. on fully manual exposure mode. You might "bias" your exposure one way or another in manual for various reasons, but that's not the same as overriding and fine tuning AE modes with E.C.

In my opinion, for any AE mode (M with Auto ISO being one of them) to be truly useful, E.C. must be possible (it wasn't on early implementations of Auto ISO on some Canon DSLRs, making Auto ISO largely useless, IMO).



This is true in a literal sense with film. But in the digital world today it will make for a lot of incorrect exposures. That's because...



... is incorrect with digital imaging.

EV charts are based upon a fixed ISO... often ISO 100. With different ISO, a different EV chart is necessary, reflecting the change in ISO. This dates back to the days of film, when you couldn't change ISO from shot to shot and long before anyone dreamed of doing Auto ISO, as is possible on modern digital cameras. Basically, you got an EV chart that related to the speed of the film you were using and could use that. (Note: ISO was most commonly known as ASA or DIN in the latter days of film. ISO combined these two into a single designation, but DIN was ultimately phased out entirely. Yesterday's ASA and today's ISO are the same.)

But you can't do the same with digital, because ISO is variable from shot to shot (you also had to change EV charts if you changed film speed).

For example, say you're taking a shot outside on a sunny day with ISO set to 100, the "Sunny 16" rule tells us for a correct exposure you would need to use f/16 and 1/100 shutter speed... Or with ISO still at 100 you could use f/11 and 1/200, or f/22 and 1/50, or f/8 and 1/400... All these settings will result in exactly the same exposure for "EV 15".

However, if you change ISO to 400 you will definitely need to change the other parameters along with it. On the same sunny day you would use f/16 and 1/400... Or, leaving ISO at 400, could use f/11 and 1/800, or f/22 and 1/200, or f/8 and 1/1600.... All of which also give identical exposure for "EV 15".

Auto ISO is the opposite of a fixed ISO. As a result, you'd need to consult a different EV chart for every change it makes, in order to make correct exposures.



The reason to set a high ISO limit on Auto ISO has little or nothing to do with EV. It's to prevent the camera from using an ISO that's so high that it causes unacceptable levels of digital noise in images. It's not talked about about as much, but higher ISOs also progressively reduces dynamic range in images, along with the resolution that's captured. You can test this yourself.... simply take a series of shots of the same subject in the same light at low, medium and high ISOs... then compare the files sizes. The higher the ISO, the smaller the file will be, indicating both a decrease in resolution and a narrowing of dynamic range.

For these reasons, it makes a ton of sense to set a limit on how high ISO the camera is allowed to use. Exactly what that will be depends upon the user and more. It depends upon what level of image noise and other image degradation they find acceptable... Plus it may depend a lot upon how they plan to use the image, as well as the overall workflow they'll be using to make the image. For example, someone shooting RAW and doing post-processing using advanced noise reduction will probably be able to use a higher ISO than someone shooting JPEGs and relying upon in-camera noise reduction. Also, someone planning to make no larger than a 5x7" print or, perhaps, only sharing image online at Internet resolutions can likely use a much higher ISO than someone planning to make a 24x36" inch print from an image. Someone planning to convert images to black & white might tolerate higher ISO and more noise than someone shooting color images, too.

johnhjacobs

When setting up auto-ISO many cameras will also let you set a minimum shutter speed as well. This can be helpful if you are using Aperture priority with auto-ISO. There are plenty of videos describing this.

kdmorris

Auto “anything” is a choice.
It’s “good” only if and when you get the results that you want...just as with Manual and Aperture Priority

I would suggest that you go out a do some street photography and see what happens.
Consider the exposure triangle when doing so, because you won’t be able to control/adjust the ISO, so practice adjusting your shutter speed on the fly.

I hope this helps.

wdross Loc: Castle Rock, Colorado

I am sure other have cover the subject heavily, but here is my two cents worth. If the shot requires a shutter speed of 150 and an aperture opening of 14, your only choice for a proper exposure is the correct ISO for the shot. If the lighting is not unusual or tricky, your meter pattern and Auto ISO should do great for you. It is really that simple.

BebuLamar

There is no difference with my pictures regardless of which mode I use. The difference is only in ease of use. Sometimes that would mean full manual.

Streets Loc: Euless, TX.

If you tink about it for a while, it could even six you a good photo.

EastWest

Unless I'm doing long exposure, I always use auto ISO and full manual. As I look through the viewfinder I can see the ISO and move the aperture and/or shutter speed up and down (thumb and finger) for the combination I think will be best. I wish the EV was easier to control without losing my sight picture.

Soul Dr. Loc: Beautiful Shenandoah Valley

I have the auto ISO set to a 800 limit in my Fuji cameras. And I can see what I SO the camera is going to to use before I push the shutter button all the way down.

splatbass Loc: Honolulu

I use auto ISO/manual mode a lot for street photography, sports and wildlife, and often just walking around so I can grab a shot quick. It works great (it helps that my D750 has excellent high ISO) and a little noise is acceptable in that kind of photography. I do not use it for landscapes or other styles that require minimum noise. For those I'll set the ISO to 100 and use a tripod if necessary.

Charlie C Loc: North Liberty, IA

There are two values of iso. Base iso and Max value. In M mode it's the floating iso that gives correct exposure up to the maximum set value. Keep the base iso at 100. This is the value used if not using Auto ISO. Maximum iso (depends on camera) but usually from 3200 - 6400. Top end cameras are often up to 12800.

raymondh Loc: Walker, MI

gdbeeler Loc: Redlodge Montana

When I'm wandering around the boonies with my 200-500 either hand held or on a monopod, with a deer on the right, something else on the left, and a bird in the sky, I really like auto iso and manual; doing landscapes with a wider lens, time, and a tripod, I switch to low iso, aperture priority. I guess it just depends on what you are shooting.

Ysarex Loc: St. Louis

ISO is not an exposure parameter -- therein lies your confusion.

From the Ilford Manual of Photography:

Exposure
When a photograph is taken, light from the various areas of the subject falls on corresponding areas of
the film for a set time. The effect produced on the emulsion is, within limits, proportional to the product of the illuminance E and the exposure time t. We express this by the equation H = Et Before international standardization of symbols, the equation was E = It (E was exposure, I was illuminance) and this usage is sometimes still found. The SI unit for illuminance is the lux (lx). Hence the exposure is measured in lux seconds (lx s).

In photography, exposure is the amount of light per unit area (the image plane illuminance times the exposure time) reaching a photographic film or electronic image sensor, as determined by shutter speed, lens aperture and scene luminance. Exposure is measured in lux seconds, and can be computed from exposure value (EV) and scene luminance in a specified region. https://en.wikipedia.org/wiki/Exposure_(photography)

The definition of exposure was codified in our discipline long before you were born and there's been no reason for it to change. And it matters as evidenced by this thread which is handing the OP a pile of bad advice.

A careful examination of the two definitions supplied won't turn up ISO as an exposure determinant. It matters that exposure is the amount of light per unit area that reaches the film or sensor. Exposure determines what the sensor will record and exposure primarily determines noise in the image (SNR).




Below is a photo of an old Hassy lens set for an exposure of 1/250 sec f/5.6. See those red numbers to the right of the shutter speed scale -- those are EV numbers and around the side if you could see it the EV value indicated is 13. ISO is in all ways unrelated. The camera (500 CM) didn't even have a built-in meter and there was no way to set an ISO (DIN or ASA) value. It was however possible to set an exposure and in the photo below it's set for EV 13. Put any ISO film in the camera you want and it will stay at EV 13 unless you manually change it. You can mount that lens to a digital Hassy body and twist the ISO knob to your hearts content and unless you manually change the EV value on the lens it'll stay set to EV 13.

The same is true of a digital Nikon or Canon set to M(manual). Set 1/250 sec. f/5.6 and you've set EV 13. If you don't manually change SS and f/stop they won't change no matter how the ISO is set. And since ISO is not an exposure determinant then the camera's exposure is manually set. Set the ISO to auto and the camera will use it's internal meter to match the ISO to the scene illuminance and the manually set exposure. Regardless of how the ISO is set the exposure is manually set.



I didn't say it did. ?



All the way back to the OP's question. He/she wants to use the camera in M(manual) mode. If the OP is setting the exposure manually (shutter speed + f/stop = exposure = light per unit area reaching the sensor) then with a Canon 60D ISO's relationship to noise in the photo will be to suppress noise.

ISO does not cause noise -- again the source of your confusion and the reason that a correct understanding of exposure matters. My niece would say duuuuh.

In this case we are interested in two types of noise that can be present in the photo. 1. shot noise and 2. read noise. With today's modern cameras the majority of what we see and call noise is shot noise. Shot noise is a function of exposure (light per unit area reaching the sensor). ISO does not cause shot noise. The confusion arises when an exposure that does not fully utilize the sensor's capacity is forced by circumstance (need for hand-held shutter speed) and a higher ISO value is used. The noise caused by the weak exposure correlates with the higher ISO value and the folks who think ISO is an exposure determinant incorrectly blame ISO as the causal agent. It's not, ISO especially in the OP's case suppresses noise.

Read noise derives from the electronics of the camera processing the sensor signal and ISO's amplification role in this instance suppresses read noise. This is camera specific and matter more or less depending on the hardware. With a Canon 60D it matters more.

The OP is establishing the shot noise by manually setting the exposure (SS & f/stop) and ISO is not part of that equation. That will account for most of the noise seen in the photo. But with a 60D it's a really good idea to let the camera set the ISO as high as it wants because that will suppress read noise.



Nonsense.

Joe

srt101fan

Are you the latest incarnation of Bipod?

Ysarex Loc: St. Louis

I am a recent participant -- no idea who Bipod may be.

Joe