# Canon auto ISO



## Stosh (Jun 26, 2010)

I have come to trust and love Canon's auto ISO feature.  I have a 5D II.  When you're outside and the light is changing, you can pick your aperture and it will pick shutter speed and ISO based on it's calculation for how fast of a shutter you'll need depending on the lens you're using.  It's also very handy for macro because the normal surface brightness rules fly out the window at higher magnifications.  From what I can tell, the camera is smart enough to know if you're using an IS lens and allows a slower shutter speed so it can have a lower ISO.  Is there any way to change the "formula" it uses to calculate this required shutter speed?  The speed it chooses is always fine for web resolutions or small prints, but sometimes when you want more detail or a larger enlargement, it doesn't choose a fast enough shutter speed (or I'm not that good at holding the camera still).

Someone is sure to tell me to use full manual or set the ISO myself so the shutter speed will be fast enough.  Duh.  I could also pull out my 20 year old light meter, find my reference exposure chart, use a gray card, focus manually, and then never look at the LCD screen because that would be too technologically advanced.  I'd just wait until my negatives were processed and printed.  That would be a lot of fun.  Obviously if I knew ahead of time that my shot was a potential poster size print, I'd do things manually. I love technology and try to use it when it can help me.


----------



## Stosh (Jun 26, 2010)

erose86 said:


> First of all... LANCASTER!  MAH HOME TOWN!!! WOOOOO!


Well at least you know how to pronounce it correctly then!  Actually, I'm half way between Reading and Lancaster.



erose86 said:


> So why not use Shutter priority mode instead?


Right, but then you don't have control over the aperture which to me is even more important than the shutter speed (unless it's set too slow lol)



erose86 said:


> Or use the exposure compensation button while in AV


Hmmm, what is this?  I always used the large dial for exposure compensation.  The problem with this is that the camera "sees" that you want to alter the exposure slightly, so it still picks what it thinks is the slowest shutter speed you can get by with and adjusts the ISO from there.  If you're already at the lowest ISO (100 in auto), then it will speed up the shutter speed.

What is the exposure compensation button?


----------



## Dwig (Jun 27, 2010)

Stosh said:


> erose86 said:
> 
> 
> > First of all... LANCASTER!  MAH HOME TOWN!!! WOOOOO!
> ...



I come from real Pennsylvania Dutch stock. I haven't lived in that area very much myself, but I have family in the area and a good portion of my family has been there for nearly 300 years.

Back on the topic of Auto ISO: It seems odd at first, but the best way to insure that you get the fastest possible shutter speed in situations with varying light is to use aperture priority (Av in Canon-ese) and set the lens to the widest usable aperture for the situation. Adding Auto ISO to the mix can help further.

When I used my old Nikon CP8400 I avoided Auto ISO. The camera was/is great and could easily compete with 10mp DSLRs with common kit lenses provided I used ISO 50 or 100. Its lens outperforms the common kit lens. Its only realy preformance limitation was elevated ISOs. 

With my current camera (Panny G1), I generally use Auto ISO. The Panny implementation has the advantage that you can set a high ISO limit. By setting this for ISO 800 I'm assured that the auto function won't shift into the 1600-3200 range without me noticing. When I need the higher ISOs and can live with the increased noise and loss of color fidelity I can set them manually.


----------



## Stosh (Jun 27, 2010)

Wow, so many Dutchies across the country!  Can you speak Dutchified?

Yes, limits would be one solution.  I'd love to use auto ISO but be able to set the shutter speed's lower limit at x.  Also using auto ISO with an upper ISO limit like you mentioned would be awesome too.  There are many times when I would take a grainier picture over a blurred picture.  Both limit detail, but in my experience, blur seems to be the larger factor unless you've got hands of steel or a tripod.


----------



## Village Idiot (Jun 28, 2010)

My 5D MKII accidentally was set for auto ISO one day when I was out photographing friends that were wake boarding. Those few shots were incredibly over exposed and complete garbage.


----------



## Overread (Jun 28, 2010)

Stosh said:


> Wow, so many Dutchies across the country!  Can you speak Dutchified?
> 
> Yes, limits would be one solution.  I'd love to use auto ISO but be able to set the shutter speed's lower limit at x.  Also using auto ISO with an upper ISO limit like you mentioned would be awesome too.  There are many times when I would take a grainier picture over a blurred picture.  Both limit detail, but in my experience, blur seems to be the larger factor unless you've got hands of steel or a tripod.



Sounds like a dream come true for me! I'll take underexposure and noise over blur - I can somewhat fix the former two and whilst I might not get a large good shot I might get something that is at least pleasing at a smaller (say web) size. The latter though, blur, I can't deal or remove in editing. 

A lower limit shutter speed would be fantastic as would an upper limit for an auto ISO.

Village Idiot - as I understand it auto ISO should work like the semi auto modes and match the ISO to the other settings to ensure a good exposure - so I'm a little confused why they would blow out your shots unless you were (say) in manual mode an forcing settings whilst auto ISO tried to keep up and got confused somewhere along the way.


----------



## Village Idiot (Jun 28, 2010)

Overread said:


> Stosh said:
> 
> 
> > Wow, so many Dutchies across the country! Can you speak Dutchified?
> ...


 
Probably. I was shooting manual and accidentally kicked it from 100 to auto instead of 50 because of the sun and trying to use a wide aperture.


----------



## Stosh (Jun 28, 2010)

Ah yes.  That would make perfect sense because auto ISO will only go down to 100, not 50.  Doesn't make sense to me why it would be that way, but it is.


----------



## Flash Harry (Jun 28, 2010)

Turn it off and use a flash, just cant be doing with AI messing up macro shots, Flash/ f16 and whatever SS you want up to sync will do the job. H


----------



## Stosh (Jun 29, 2010)

I guess it all depends on one's definition of macro.  When I'm using the MP-E 65mm with 1x to 5x magnification, I'm with you - flash and mostly f/16.  But when I'm using the 100mm macro with IS (where I'm not always shooting at its maximum of 1:1), I mostly prefer natural lighting and varying apertures depending on the situation.  I tire of the flash look.  It has great saturation and contrast, but backgrounds are often black and look too fake.  Ambient light allows the background blur to show colors and textures you just can't get with a flash.  That IS is an awesome lens.


----------



## Overread (Jun 29, 2010)

shhh shhhh I already have 3 macro lenses and everyone is raving about this 100mm IS.. I don't need 4!!


----------



## Garbz (Jun 29, 2010)

I'm not taking the piss, and no pun intended either, but have you considered drinking before you shoot? One quart of wine should do the trick.

That got me through my thesis. I was fuelled through uni by a steady stream of caffeine and my hands shook a lot so every time I did some surface mount soldering with a microscope I drank a glass of wine first. Did wonders for steadying my hands.

Also on the topic of just shooting manual, you do realise that your lightmeter still works in manual right? There should be an indication in your viewfinder of how your current settings compare to the camera meter. Also in manual if you set AutoISO you still have that aspect being done automatically. You could manually dial in your aperture and shutter speed, and exposure compensation if needed and let the camera figure out the required ISO.


----------



## Stosh (Jun 29, 2010)

Garbz said:


> I'm not taking the piss, and no pun intended either, but have you considered drinking before you shoot? One quart of wine should do the trick.
> 
> That got me through my thesis. I was fuelled through uni by a steady stream of caffeine and my hands shook a lot so every time I did some surface mount soldering with a microscope I drank a glass of wine first. Did wonders for steadying my hands.
> 
> Also on the topic of just shooting manual, you do realise that your lightmeter still works in manual right? There should be an indication in your viewfinder of how your current settings compare to the camera meter. Also in manual if you set AutoISO you still have that aspect being done automatically. You could manually dial in your aperture and shutter speed, and exposure compensation if needed and let the camera figure out the required ISO.



Very cool Garbz.  Not only does drinking sound fun, but also scientifically viable - not that it wouldn't be much different from my normal routine anyway lol.

Yeah, I've considered using manual with auto ISO, but spoiled me wants my cake and eat it too.
Canon's formula for shooting aperture priority with auto ISO seemingly goes something like this:
Choose lowest ISO until shutter speed gets to x (where x is calculated using focal length and whether or not it has image stabilizer).  If shutter speed needs to be lower than x, increase ISO to keep shutter speed at x.

I would love some fuzzy logic that says if we're approaching shutter speed x, why not just raise the ISO to 200 or even 400 (both of which have very excellent results) to keep the shutter speed a stop or 2 faster than x.  Then when you start approaching the need for ISO 1600 or above (or maybe 800), then start slowing down the shutter speed to x.
It really wouldn't be that hard to implement.  Since that's not happening, user defined ISO and shutter speed limits would be the next best thing.  Since that's not happening either, your method of manual is probably next best.

It's just frustrating because when you are processing and you find a shot you really love, you start pixel peeping and find that everything is blurred 8 pixels long (probably worst case).  No big deal for web resolution, but speeding up the shutter 2 stops would have cut that 8 pixel blur to a 2 pixel blur.  This would have come at a cost of some noise, but certainly not an 8-pixel blur worth of noise!



Overread said:


> shhh shhhh I already have 3 macro lenses and  everyone is raving about this 100mm IS.. I don't need 4!!


But you DO need 4 macro lenses!  At least the price is *significantly* lower now than when I bought it.


----------



## mishele (Jun 29, 2010)

:thumbup:


----------

