Issues w/ T7i auto ISO--help pls

[ehammarlund]

I just switched from Nikon D200.  I'm looking for a setting which will allow me to shoot aperture priority but which will maintain the shutter speed at a set minimum by adjusting the ISO as needed (auto ISO.)  I can see the ISO automatically increasing so there seems to be some sort of auto ISO.  But it doesn't start until shutter speed is too long, which makes it entirely useless.

It was my goto setting on my D200; I can learn to live without it if I must but am I just missing it somewhere?  How can I tweak minimum speed?

[kvbarkley]

You can't. Canon only lets you set the maximum ISO.  This is where Nikon is better than Canon.

[jrhoffman75]

Actually it’s a function of camera level. 1D X let’s you set Auto ISO range (min and max). I don’t know if it goes to intermediate models.

The T7i is an entry level model. Analogous to Nikon Dxxx models. The D200 would be more like Canon XD models.

[ehammarlund]

Oh well, what a bummer. That was always the perfect line between manual and automatic control; it's always a pity when companies delierately screw up something so simple just to make their price points different enough.

[ehammarlund]

thanks, though, for letting me know the bad news 😉

[Waddizzle]

---

@ehammarlund wrote:

thanks, though, for letting me know the bad news 😉

---

I suggest that you check your camera menus, and read the instrution manual.  I have a Rebel T5, and I can set a maximum setting for Auto ISO mode, which means I can set a range from ISO 100 to a maximum value.  I have no doubt that your T7i can at least set a ceiling for the ISO Auto mode.  

[kvbarkley]

We know you can set a max ISO, he wants to set a minimum to increase shutter speed.

[Waddizzle]

---

@kvbarkley wrote:

We know you can set a max ISO, he wants to set a minimum to increase shutter speed.

---

Dial it in manually.  Personally, I think the OP has an issue, and is trying to solve it in one specific way, perhaps the wrong way.  The actual issue is not with ISO, but with the automatically selected shutter speed in Av mode. 

The camera algorithms have known “bias” to adjust settings in a certain way when you allow it to adjust two, or more, legs of the exposure triangle.  If you do not like that “mindset”, then adjust the settings manually.  Personally, I never let the camera adjust more than one leg at the same time for that very reason.

I say put the camera into manual mode with ISO Auto, and manually adjust shutter speed.  Problem solved.

[ehammarlund]

I say put the camera into manual mode with ISO Auto, and manually adjust shutter speed.  Problem solved.

---

So if I'm at 1.8/250 and auto ISO, it will adjust the ISO to keep the exposure correct even though I'm in manual mode? It never occured to me it would do that--I thought manual mode required you to set everything.

i'll give it a try; thanks--that will work in many situations.

That said, there's a good reason I am trying to make this work, maybe I can explain it better: When AUTO ISO is implemented properly, the "bias" is the point. 

Auto ISO works best in aperture priority mode.  It is supposed to simply use the lowest possible ISO, for the aperture selected, while keeping the shutter speed above a set minimum.  If the sun comes out from behind a cloud, and you have "extra" light, it'll simply shorten the shutter speed to account for the increased exposure (after all you're still in aperture mode) and if the clouds get thicker it'll simply raise the ISO (without dropping shutter speed above minimum.)

The solution you propose sounds like it will properly accommodate for a decrease in light (by raising ISO) but I'll have to manually adjust shutter speed if the ISO is low and the light increases. 

This whole thing is only an issue because I only have one adjustment wheel.  I used to have two wheels; one for aperture and one for ISO / Shutter (as needed) and I'm trying to work around it.

[Waddizzle]

“That said, there's a good reason I am trying to make this work, maybe I can explain it better: When AUTO ISO is implemented properly, the "bias" is the point.”

No, that is not how or why Auto ISO is implemented.  The “bias” I spoke of doesn’t kick in until you allow the camera to automatically adjust two or more legs of the exposure triangle, and it does not matter which two.  Auto ISO has nothing to do with it.  ISO is just another leg on the exposure triangle.

“Auto ISO works best in aperture priority mode. It is supposed to simply use the lowest possible ISO, for the aperture selected, while keeping the shutter speed above a set minimum. If the sun comes out from behind a cloud, and you have "extra" light, it'll simply shorten the shutter speed to account for the increased exposure (after all you're still in aperture mode) and if the clouds get thicker it'll simply raise the ISO (without dropping shutter speed above minimum.)”

Auto ISO works the same way in any Creative mode.  It is adjusted to correct for proper exposure.  This is done after the camera has set aperture and shutter speed, not before, as you seem to suggest.  I suggest only allowing the camera to automatically control only one leg of the exposure triangle.  This gives you greater control over the end result. 

“The solution you propose sounds like it will properly accommodate for a decrease in light (by raising ISO) but I'll have to manually adjust shutter speed if the ISO is low and the light increases.”

No, depending upon the current exposure settings, and the amount of change in light, either could happen, for either case.  If ambient light increases, you may or may not have to adjust shutter speed.  Likewise, if ambient light decreases, you may or may not have to adjust shutter speed.

“This whole thing is only an issue because I only have one adjustment wheel. I used to have two wheels; one for aperture and one for ISO / Shutter (as needed) and I'm trying to work around it.”

All that you really need is one adjustment wheel.  The camera has two buttons, one for aperture and one for ISO, which temporarily repurpose the main wheel to adjust aperture or ISO.  You just need to practice using the camera.