Using AV

Discussion in 'Canon EOS Digital SLRs' started by Matt Canon 80D, Feb 3, 2024.

  1. Matt Canon 80D

    Matt Canon 80D New Member

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    Hi everyone. I have been practicing with the AV mode on my EOS 80D. I had it set at F3.2. The ISO was 640, shutter speed was 1/500 for a sequence of shots, then went to 1/1600 and the pics were all clear. However the shutter speed suddenly jumps up to 1/8000 plunging those pics into darkness! Can anyone help with why that happened and how I avoid it in future? I was shooting runners, outside if that helps!
     

  2. Caladina

    Caladina Well-Known Member

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    was the iso manually set / locked in or auto? what type of focus boxes were you using, multi or single box

    possibly the reason yours went to 1/8000 it must have caught a highlight and exposed for that?

    personally i shoot manual rather than either of the semi auto ones, tv or av as i shoot wildlife mostly, also single box so i can point the camera onto the subject i want rather than have multi box think i want the background

    way i see it is if my settings are off for an image (i shoot efv mirrorless so i have simulation on for exposure) then i know where my settings are for look free adjustment, ie the camera hasn't changed anything i dont know about or want
    if shooting semi auto then i may have to look see what the camera changed then change that and the one that i wanted to change
     
  3. johnsey

    johnsey Site Moderator Staff Member Site Supporter

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    Right as noted by Caladina the auto exposure adds variables based on the evaluation of the scene in that given moment of making the photograph. That said if it was the middle of the day I would find that much variation in lighting a bit difficult to expect.

    Since its AV mode we know you locked in the F3.2 which is a very wide aperture letting in a lot of light and making the background nice and soft very quickly. I am not sure about the ISO but i will just assume the 640 was locked in manually, since you said the images got quite dark which means the camera doesnt seem to be adjusting to an iso change.

    Is it possible at all you bumped this into manual mode and the dial was adjusted to the 1/8000, or that you added in exposure compensation using the +/- button and the dial???? Moving from 1/500 to 1/8000 is actually only 4 stops of light. so its not a crazy thing to think it was dialled in on one of the dials by accident.

    upload_2024-2-3_16-51-19.png

    500 to 1600 is about 1.5 stops and you would likely start to notice the underexposure on the LCD but it would be usable...To me it feels like you may have been spun the back dial while shooting and adjusted something manually. If you have strong lighting variance in the scene it is possible the camera exposed drastically different as you pointed at things but that implied you had some strong back or front lighting. (for a good example or two......think silhouette of someone in-front of a sunset, or a blown out background of bight outside scene when a person stands in front of a window but you expose for them indoors where it is much darker in comparison and the outside goes almost white.
     
  4. Matt Canon 80D

    Matt Canon 80D New Member

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    Thank you. I really appreciate your feedback. I had set the ISO manually and I had multi, central focus box set rather than just a single. It may have jumped around as I set up the shot.
    Thanks again.
     
  5. Matt Canon 80D

    Matt Canon 80D New Member

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    Thank you for such a detailed reply. I checked back and did have exposure compensation dialled in so I wonder if that caused the jump? It had quite an effect on the shot!
     
  6. johnsey

    johnsey Site Moderator Staff Member Site Supporter

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    It can impact a fair amount but is a math equation, where it will impact the shot exactly how much was dialed. so if you for example dialed in -2 stops (underexpose), it would double the shutter speed twice from that 1/500 to 1/2000 respectively as an example. I say shutter because you were in aperture priority so that was locked in.
    If you have 2 or 3 stops dialed in, it would definitely be enough to darken or wash out an image depending on which direction it was dialed. If your a bit green to the idea of a stop, each full stop is either cutting in half or doubling light it allows. 1/60 to 1/120 sec or 1/1000 to 1/2000 are 1 stop differemces, as are f2.8 to f4 or f5.6 to f8. So if light is halved or doubled each step it adds up very fast on impact to the image.
     
  7. Caladina

    Caladina Well-Known Member

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    also if your camera allows you to have the histogram in the veiw finder or on screen when shooting (i realize this might not be possible with the optical view finder, but not totally sure) its a very good indicator on exposure

    i wasn't going to add this but someone may be reading with that option, its certainly one of the key features that helped my learning to nail exposure as a beginner and today
    might only be a mirrorless feature for the view finder
     
  8. Matt Canon 80D

    Matt Canon 80D New Member

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    Thanks Johnsey, that's really helpful. I'm gradually learning the ropes and am moving away from full auto so this really useful.
     

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