01 April 2021

Taking advantage of Auto ISO - Official Canon Article

Taking advantage of Auto ISO is an official Canon Learning document. 

Using Auto ISO 500 with Canon EOS 7D Mark II - Image: Vernon Chalmers Photography
Using Auto ISO 500 with Canon EOS 7D Mark II - View Gallery

Using Auto-ISO for Birds in Flight Photography
Many of my Canon EOS photography clients / students uses the Canon EOS-1D X II, Canon EOS 5D Mark III/ IV and Canon EOS 6D / II and high-end APS-C / Crop bodies (EOS 7D Mark II / EOS 90D / EOS 80D / EOS 70D amongst others). This article is an excellent resource to inform them of the official Canon motivation on using Auto ISO.

I only use Auto ISO for my birds in flight photography and for many new birds in flight photographers this is quite a departure from pre-set ISO's

I have used Auto ISO since 2013 for serious birds in flight starting with the Canon EOS 70D and rarely had noise issues up to ISO 1200 (with some noise reduction applied in post-processing).

Taking advantage of Auto ISO
Canon’s EOS-1D X, EOS 5D Mark III and EOS 6D possess a host of new features and improvements, including a significant refinement of Auto ISO, that makes the feature an even more practical option to working photographers and serious enthusiasts. Aside from the cameras’ outstanding high ISO image quality and significantly increased ISO range, the following features answer the requests of many serious shooters:
  • User can manually pre-set a minimum and maximum ISO range
  • For Auto ISO, the shooter can pre-set the minimum and maximum available ISO range (this is separate from the range for manually-adjusted ISO)
  • For the first time with an EOS SLR, the shooter can set a minimum shutter speed used with Auto ISO. If the shutter speed drops below this user-set value, the Auto ISO will automatically be raised

Auto ISO has become a feature many experienced SLR users are considering in certain shooting situations. This article will cover in detail these new settings and offer some possible scenarios where they might prove very useful.

Auto ISO
The EOS-1D X, EOS 5D Mark III and EOS 6D allow Auto ISO to be used in all shooting modes, including Manual mode, and all the ISO speed options are accessed from a single screen. But for many experienced shooters, the first question may be, “Why would I want to have the camera automatically set the ISO for me?”

One example is when lighting may change radically during shooting. Theater and concert photography, where stage lighting may change rapidly, are really good examples. Wedding ceremonies in churches are another example. With available light in the church, the photographer would have to speedily adjust when the doors open and the couple exits. Without missing a moment, Auto ISO would let the photographer work at higher ISOs indoors and seamlessly switch to lower ISOs outside.

Sports events that occur in the early morning or late afternoon, where half the field may be in direct sunlight and the other side in deep shade, are also challenging. Professional sports photographers used to have a few choices to deal with this situation, such as pre-setting exposure settings for only one side of the field. Another possibility would have been carrying two cameras, each pre-set to different settings and film speeds, and switching between fields. I doubt many photographers miss doing that.

A wildlife photographer suggested this challenging scenario: he or she is following a running animal, which means that the shutter and aperture can’t be easily changed. The animal might hide under the shade for a moment before suddenly running into bright sunlight. Adventure photographers, like rock climbers, might face the same challenge with dramatically different lighting situations when facing up or down from the same spot.

If a photographer shoots in Av or Tv mode, they may anticipate needing or wanting to make major changes in aperture or shutter speed, respectively. Auto ISO can save time by preserving a reasonable hand-held shutter speed (in Av) or usable lens aperture (in Tv), which possibly eliminates the need to follow-up with a big Av or Tv change with a manual adjustment of ISO.

In Manual exposure mode, a pre-set shutter speed and lens aperture can be continually maintained, even if the light changes. This allows the photographer to have full control over stopping motion and depth-of-field, while still allow the camera to react to any changes in light (this could be ideal in remote-controlled or intervalometer shooting). A very handy, yet underutilized, feature is the ability to apply AE Lock when working with Auto ISO in Manual mode. The viewfinder will show the difference between the locked value and the current metered value. It is important to know that the camera won't let you use the “ealxtended” ISO settings (equivalent to ISO 50, 51200 and 102400 on the EOS 5D Mark III and EOS 6D) in Auto ISO.

Shutter Speed
Until now, one problem that kept many pros away from Auto ISO was that there was no meaningful control over how slow a shutter speed might be selected in low-light conditions. But with Canon’s recently introduced SLRs, the photographer can tailor Auto ISO to give exactly this type of control. A separate menu entry, Minimum shutter speed, provides the following settings:

  • Auto: Camera will continue to try to maintain a shutter speed of at least 1 over the lens focal length, changing ISO to maintain this as long as possible. The camera will tend to pick lower ISOs and slower speeds when using standard or wide-angle lenses.
  • User-defined shutter speed: Photographer can pick a speed from 1 second to 1/250 of a second and the camera will only go below this shutter speed after it has raised its ISO to the highest available setting, based on Maximum ISO set by the user under Auto ISO range.

Some users are often hesitant to delegate such an important setting to the camera’s brain. But after getting used to this new feature, the results speak for themselves.

Image Quality
Thankfully, Canon thought about image quality at great length and came up with very elegant solutions. Users can specify the slowest shutter speed before the ISO is raised automatically and they can set a limit to the highest ISO the camera will use, which enables them to retain the lighting and look that they desire for a scene. They can also specify the ISO range the camera can use to ensure proper image quality.

The overall image quality at higher ISOs on Canon’s latest full-frame digital SLRs is superior to any Canon EOS models which have come before them — making shots at higher ISOs a legitimate and practical option, even for critical shooters. Just a few years ago, ISO 400 or 800 provided image quality that was borderline acceptable. With current systems, one can now push the ISO to 3200 and higher and get vastly cleaner files. This point certainly means Auto ISO is here to stay.

Flash and Auto ISO
When using a flash on the EOS 6D, 5D Mark III or 1D X, photographers need to be aware of these settings:

  • Auto ISO normally is locked at ISO 400 when an EOS speedlite is attached and turned on
  • Auto ISO can be lowered down as far as 100, if over-exposure would occur in fill-flash situations in bright outdoor lighting
  • If an EX-series speedlite is swiveled for bounce, Auto ISO can extend from 400 or up to 1600 (depending on level of ambient lighting in the scene) and allow for an extra measure of E-TTL exposure when flash is scattered by bouncing

Even though one can’t set maximum and minimum ISO or shutter speed when shooting video, video shooting with EOS SLRs does permit use of Auto ISO. When recording video with an EOS SLR in any Auto mode (P, Tv, or Av), ISO is always set automatically by the camera.

When shooting in Manual Mode, users can set a specific ISO (from 100 to 12800; up to 25600 on the EOS-1D X) or let the camera automatically adjust the ISO on the fly. The beauty of this is that the photographer’s choice of shutter speed and lens aperture, often critical when recording HD video, can be pre-set and locked in. Yet, if lighting changes as the camera or subject moves, the camera can adjust exposure by only varying ISO. Again, when shooting video and the camera is set to Program (P), Aperture Priority (Av) or Shutter Priority (Tv), the only option users have is to let the ISO be automatically set by the camera.

If you are shooting from a moving vehicle — for example, a car or a train — you may be going through a whole range of scenes from bright to dim light. Another situation when Auto ISO is very helpful is when shooting one continuous shot with a Steadicam. Auto ISO comes in handy when going from a very dark scene (an underground Subway platform) to a very bright scene (a street at midday) when one does not have easy access to the camera settings while recording.

As you can see, Auto ISO is a very useful setting when the light is changing rapidly and either the shutter speed and/or aperture need to be pre-set to match a specific effect – like freezing action for sports or wildlife, or when changing settings is not easy. It can enable very quickly and make major changes to speeds or apertures, thus allowing the user to shoot again without having to make a follow-up adjustment to ISO.

When working in situations with rapid and extreme changes in lighting, consider using Auto ISO more often, especially when capturing the moment is absolutely critical.

An In-depth Discussion of M + Auto-ISO for Canon SLRs View

Source: Canon USA

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