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. 

[Waddizzle]

Are you “shooting” stills or videos?

What is your shooting mode?  

More than one shooting mode allows you to manually set a shutter speed.  The Tv and Av modes are able to override your setting if shooting conditions warrant it.  When you are using M mode the camera should not be able to override either shutter or aperture.

[mikellherrick]

Always in Manual Mode...that's why I can't figure out why the override is occurring.  And this occurs with still photos...not video.

[Waddizzle]

If you are in M shooting mode, then shutter and aperture should not change on their own.  How is your control ring on the lens programmed?  I keep mine disabled.

[EDIT] If you are using a Custom Shooting mode, then the settings can revert to the custom defaults when the metering timer expires.

[mikellherrick]

It took me a bit to find that in my menu because I've never used it before...and looks like the control ring was set at the default "exposure compensation" ...so I disabled that.  Do you think that was my problem?

[Waddizzle]

---

@mikellherrick wrote:

It took me a bit to find that in my menu because I've never used it before...and looks like the control ring was set at the default "exposure compensation" ...so I disabled that.  Do you think that was my problem?

---

Yes, it is entirely possible.  Turning the control ring will make some change on the exposure settings.  There is a secondary control ring located at the power switch, which can also change exposure settings.

The big one is the lens control ring.  I leave it disabled!

[mikellherrick]

OK...I will see if this makes any difference and hope I don't get those changes to shutter speed.  Thanks. 

[BurnUnit]

Does the R7 have Canon's "Safety Shift" feature? Maybe try disabling it if it is currently enabled. Though I would agree that when shooting in M mode it shouldn't function at all.

[mikellherrick]

I checked...and yes...there is a Safety Shift option in the menu...and it is OFF....so that's not going to help.  It is a mystery to me why the shutter speed changes on its own...and to be clear...this doesn't happen all the time...just once in a while...mostly when shooting in low light I think. 

[p4pictures]

Did you activate same exposure for new aperture in the custom functions. If so there are three options ISO speed, ISO and shutter speed or lastly just shutter speed. 

This function is designed to give you consistent exposures as the aperture value changes. Your 100-500mm changes the widest aperture between f/4.5 at 100mm and f/7.1 at 500mm. Say you set 100mm on the lens and set the shutter speed to 1/400 and fixed the ISO. If you have the custom function set to change the shutter speed, then as you zoom the lens goes to f/5 and the shutter speed reduces 1/3-stop, then f/5.6 and another 1/3-stop of the shutter speed. 

So if it was 1/400th at 100mm and f/4.5, then it would be 1/160th at 500mm when the aperture is f/7.1. Personally I use this function, but have the camera override my ISO choice instead of the shutter speed. I can more readily deal with 1 1/3-stop more ISO than I can a drop of shutter speed.