Canon R7 wi/RF 100-500 keeps changing shutter speed while in Manual

[mikellherrick]

I've been noticing that while shooting (often in low light) my R7 will automatically change my shutter speed to 1/125 even though I have manually selected 1/400 typically. ISO is always on Auto and aperture at widest allowed for conditions.  Is that normal?  Is it because the camera thinks I can't get a good shot shooting that fast?  If I move my frame around a bit...or reset the manual speed back to 1/400...it will usually allow me to use that speed.  It is annoying because I'm also shooting in continuous mode (mechanical) and find I'm getting overexposed or blurred images when this happens. 

[mikellherrick]

I haven't used custom functions at all...something to check out maybe.  I pretty much always set the ISO to auto since I'm doing wildlife/bird photography for the most part and dealing with quickly changing light situations with moving subjects.  Shutter speed is something I adjust more and I often leave my aperture as wide as possible because I also shoot in low light conditions.  Most of the time my shutter speed is set somewhere between 1/400 and 1/1000 ...so it was just weird to experience the camera changing the speed to 1/125 spontaneously ...I almost never set it that slow.   

[stevet1]

mikellherrick,

Another possibility might be, even though you have ISO set to Auto, have you set a limit on how high your ISO can go?

If you have set a limit, once your camera hits that limit, it has no choice but to adjust your shutter speed.

Just a thought.

Steve Thomas

[mikellherrick]

OH...that's interesting.  My ISO speed settings are:  ISO speed - Auto....ISO speed range - 100-6400....Auto range 100-12800...Min. shutter speed - Auto.  I always use Auto ISO...but should I change the ISO speed range to a higher ISO than 6400?  I think you might be on to something.  I did set this a little lower because I was concerned I might be getting too much noise in low light photos with really high ISO limits...but of course I might just be trying to shoot too fast for the light conditions. 

[stevet1]

mikellherrick,

You might give it a try and see if it helps.

A full stop will take you to 12800. One-third stops will take you from 6400 to 8000 to 10000 to 12800.

Shooting high speeds in dim light is tricky. There's trade-offs. You may have to accept some noise to get the shot rather than winding up with a blurry shot because of too low of a shutter speed.

PS: Newer cameras are handling higher ISO numbers much better then they used to.

Steve Thomas

[mikellherrick]

I was still experiencing this problem of the camera switching my chosen shutter speed to a slower 1/125th no matter that I manually set it faster.  I realized today that it only happens when I am fully zoomed in to 500mm...and that if I back off a little it reverts to the faster speed.  This seemed weird still...so I took a closer look at my lens settings and saw that I had it set at FULL instead of 3m to infinity.  Not sure when it got set to that...but it's been a while since I looked at that setting.  Once I switched from FULL...I found I could zoom in fully and my shutter speed didn't change.  I'm hoping this might have been my problem...not totally sure because this problem was happening only sometimes.  Fingers crossed that this did the trick...and if anyone can explain why this might have been the problem...I'll be happy to know I'm on to something here.

[p4pictures]

Since you are using manual exposure, what aperture do you chose when taking photos?

Secondly I am not sure the focus range switch on the lens would change the aperture reported to the camera. It should only restrict the distance the lens focuses over to between 3m (10-feet) and infinity. Most lenses have fine steps of focus at closer subject distances, so by restraint the focus range your lens avoids having to hunt for the focus in the closer distances. Setting FULL or 3m to infinity should have no restriction on the zoom setting, certainly it didn't when I used the RF 100-500mm lens. Are you also using a 1.4x or 2x extender? These do limit the zoom range of the lens, it can only zoom from 300mm to 500mm when an extender is fitted.

[mikellherrick]

I normally use the widest aperture I can because I'm often shooting in low light conditions and faster speeds ...wildlife...moving subjects...so the widest is f7.1 when I'm fully zoomed to 500mm.  I don't use an extender.  It's just the shutter speed that changes on me.  I can set  1/400th or faster...and sometimes when I'm zoomed in to 500mm...the camera changes my speed to 1/125th while I'm shooting...resulting in an overexposed or blurred shot.  ISO is always on Auto.  I noticed that if I backed up slightly on the zoom...the speed returned to my preset faster speed.  This is still a mystery to me. 

[Waddizzle]

Forum member p4pictures is correct.  Your lens switch setting is unrelated to the exposure settings within the camera.  Check the setting he is describing.

[mikellherrick]

OK...so that's not the solution then....I am hoping that another suggestion to increase my ISO range in the settings to a higher ISO will prevent my camera from decreasing speed when a higher ISO is necessary to get a good exposure.  That makes sense to me...but I'm still not sure because it doesn't happen all the time.  I'm waiting to see if it happens again with a higher ISO limit.

[barrybee]

Have you tried p4pictures suggestion to change "same  expo. for new aperture" - custom function setting item #2 (C.Fn2)- to either "OFF" or "ISO"?