1. omens

    omens

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    I was at my extended family's party this weekend. Posed group photos so nothing fancy. Indoors. I metered off my brother-in-law's face (who has a dark complexion as it is) and started taking photos. External flash (in hotshoe) was in ETTL mode. The initial exposures were 1-2 stops underexposed. I was in Av mode so added +1 EC. Exposure was a bit better. Ended up with +2 EC which was slightly overexposed but I started getting that wraparound effect on peoples' heads from the light from the window behind them.

    ISO was in auto but never went above 400 for some reason. Instead the camera started dropping shutter speed down (going down to 1/6 for some shots) which meant some shots were blurred. Using 18-135mm lens and generally at 50mm so f/5 aperture.

    In hindsight, I should have just stuck the camera in manual mode, dialled in the exposure I wanted and taken the photos. But everything started happening very quickly, so I didn't have time for test shots.

    Is there any reason why my 70D didn't bump up the ISO higher than 400?
     
  2. Bythesea

    Bythesea

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    Brian
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    I don't know the 70D, but auto ISO often has an upper limit that can be set. It may be that yours is currently set not to go higher than 400 but this should be changeable in the settings.
     
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  3. KIPAX

    KIPAX Waldorf

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    I know in the canon bodies i use Auto ISO doesnt usualy go above 400 when using flash in any auto or semi auto mode... so its not somehting wrong with camera or settings....
     
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  4. troutfisher

    troutfisher

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    I seem to recall from my Canon days that in AV mode when you attach the flash the camera defaults to ISO 400.
    Indoors put the camera to manual, aperture to suit, shutter at or below sync speed, iso 400 ish , flash to ETTL , ignore the meter and adjust FEC on the flash.
    In AV mode the flash is acting as a fill light, in manual it is acting as the main light.
     
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  5. omens

    omens

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    Thanks all. It does look like ISO is limited to 400 with flash attached. I imagine that's why shutter speed had to drop.

    I was using bounced flash as fill primarily hence left in Av.
     
  6. KIPAX

    KIPAX Waldorf

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    if iso cant go up then shutter will drop as you already set the aperture.. if in sv mode then the aperture would ahve changed and shutter would have stayed same..... Am guessing if one or the other maxed out then the iso would change...
     
  7. omens

    omens

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    It was a f/3.5-5.6 lens so even if I set the aperture at 3.5 when the lens was zoomed out at 18mm, at 50mm aperture would have dropped to f/5 and I couldn't open it any wider.
     
  8. Mr Badger

    Mr Badger

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    :agree:
     
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  9. Bythesea

    Bythesea

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    If you don't have the manual, you can download it from here. As stated above when a flash is attached it is set at 400, though on pages 122-123 it tells you what settings are used for auto ISO in other modes, and how you can adjust them.
     
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  10. Phil V

    Phil V

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    As @troutfisher says,

    I’d go as far as to advise never using auto iso with flash, never use AV mode when flash is your primary light source.

    Use M, set an exposure to underexpose your ambient by a comfortable amount, let ETTL do all the heavy lifting, it’s simple and works brilliantly.

    If you want to fry your brain there’s a guide to the algorithms used for flash with Canons auto modes, reading it may lead you to choose never to try using them again. In a nutshell, the camera will try to decide whether to favour the ambient and use flash as fill, or that the ambient is so low it should use the flash as main, but as you’ve found, it drops shutter speeds to favour the ambient forbfar too long.
     
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  11. omens

    omens

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    This was indoors so indoor lighting (with some light coming from a window that had the blinds closed (to hide some of the mess in the garden)). I reckon if I hadn't bothered with flash, the auto-iso would have happily boosted up to 800+ so the shutter speed wasn't so slow. I wanted some fill flash, since more light was coming from behind the family.
     
  12. Phil V

    Phil V

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    My advice stands, I avoid using Canon auto modes with flash, it’s simply not predictable (as you found)
     
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  13. holty

    holty

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    reset camera to factory settings and the try manual mode
     
  14. Mr Badger

    Mr Badger

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    Why reset to factory settings, the camera seems to be behaving exactly as its supposed to? :confused:
     
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  15. holty

    holty

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    just incase the op has disabled or enabled a setting that stopping camera from letting iso go up
     
  16. Phil V

    Phil V

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    The cameras designed to fix the iso when the flash is switched on. It’s not something that’s been set in a menu, it’s doing exactly what I’d expect it to.
     
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  17. omens

    omens

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    This.

    I did an trial just now. Stick flash on camera, switch both on and meter some shots in a reasonably dim room. ISO is fixed at 400. Switch flash off and do nothing else, repeat. ISO jumped up to 1000. Stick flash on and it went back down to 400.

    What bothers me more than anything is that normally, if I'm using my external flash, I will set up everything for manual. I will set the aperture, shutter speed, iso and (usually) flash all manually to get the exposure I want. Especially in a situation like this where the room light wasn't going to change and it was essentially group poses in the same location.

    I'm going through the photos in lightroom today and hopefully it won't be too much of a disaster.
     
  18. HoppyUK

    HoppyUK

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    But as so often happens, only after you've read the handbook ;)

    No disrespect to the OP here, it is a slightly counter-intuitive feature, but after a few years on photo forums I'd say RTFM would solve around 90% of the 'my camera's broken' questions.
     
  19. swanseamale47

    swanseamale47

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    wayne clarke
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    Canons usually have the option in custom functions (for AV mode) to set either a fixed 1/250 sec, 1/60 -1/250 variable sec or a third option which I cant remember offhand) AV probably isn't the best option if your using flash as a main light IMHO.
     
  20. omens

    omens

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    Bit harder to do when you're out shooting and the manual's at home.The stupidest thing is that I could overridden the ISO manually, gone for a higher ISO which would have reduced shutter speed. As it stands about a quarter of the photos were taken at 1/30 or less and these were handheld images of people in a group (and won't stand perfectly still as a statue).
     
  21. HoppyUK

    HoppyUK

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    You can download the handbook as a PDF file and put it on a smartphone.
     

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