ISO question.

[powerslave16v]

A quick question about ISO speeds.When i had my 100-400 mk1 lens i always used AV mode set at f8,this was to get the best out of the lens.
The iso would usually be left at 125,resulting in some lowish shutter speeds for fast jets (mind you thats prob because of the f8 aperture).
Anyway since i got the mk 2 100-400 lens i shoot at f5.6 resulting in a faster shutter speed,so still keep the aperture set at 125.
The question is when i trawl through flickr and the like i see shots taken in bright light at various iso ranges from 100 upto 400-500.
Would you say this is becasuse the camera is set at auto iso,i know increasing the iso in the old days would increase noise (not so much now with moden dslr's though).
I always try to keep the iso down,not sure if putting the 70D in auto iso would make much difference when i have a shutter speed off 1/1000th since i shoot at f5.6 with the mk 2 lens.
Would welcome any comments on this please.

Ian

[harvo266]

Hi,
It depends on the light conditions, but in a nutshell all camera's work the same i.e. if you were to copy my settings then we'd have the same shot, same lighting etc. You need to think about what you want from the photo (Sharp picture guaranteed - High shutter speed, the whole photo clear - wide aperture, or a clear picture - low ISO) but if you are knowledgeable on the settings then all 3 work together. I shoot in manual mode and only tend to use two settings in fairly good conditions - 1/2000, f5.6, ISO320 (most aircraft) or 1/160, f12, ISO 125 for prop aircraft. Then i just alter them very slightly according to conditions

A general rule of thumb I go by is don't go higher than around ISO800, lower than 1/125 (handheld) so that the photo is clear and sharp.

Hope this is of some help

[powerslave]

Thanks,just wondering why you use Iso 320 when you are getting 1/2000.
I've been getting 1/2000 at 5.6 on iso 125 and they are pin sharp.
So what would the difference be between my iso 125 shot and your iso 320 one?
Ian

[Nighthawke]

Unless I'm missing the point, quite simply a difference in available light.

[harvo266]

Yeah exactly Nighthawk - you probably had better lighting meaning you can tone the darkness down a little bit and also adding quality (lowering ISO)

[powerslave]

Yeah exactly Nighthawk - you probably had better lighting meaning you can tone the darkness down a little bit and also adding quality (lowering ISO)

Okay thanks,even in bright conditions I suppose some of my images are slightly dark even though I'm shooting with a highish shutter speed and iOS 125.,but I was using f8 with my old Mk 1 lens.
So using AV 5.6 would you think I would be better using auto Iso than setting it to iso125?
Would this give my shot a better exposed picture ie a bit brighter.

Ian

[davem]

Although not many will agree, I'm a fan of 'P' Mode as this will allow instant control of shutter speed by changing aperture using the selected 'wheel' control depending on which model of camera you've got. Easy for changing between shooting jets and then props / helis when you want to achieve blur.
All you've got to remember is to keep an eye on the viewfinder display (which I am guilty of not doing) but I've ruined that many photos by leaving the camera on either Av or Tv and forgetting I've done it that it's been 'P' for me for a while now.
If you can't then achieve a decent shutter speed by changing aperture then it's time to up your ISO.