EOS RP - General Usage Questions

[DHenry]

Hello    I have a question about my EOS RP camera.  i received this camera for Christmas last year.  I actually have two questions.

1)  When I put this in manual mode and use my zoom lens (lens that came with it, RF 24-105 mm) it does not hold my settings when zooming in and out.  Example if I set my F-stop to 4.0 and zoom in on my subject my F-stop will change to 7.1, my ISO and Shutter will stay the same.  Why is that.  My old camera (80D) always stayed where I put my settings in manual mode.  

2)  I have an adaptor to put on it so that I can use one of my EF Lenses to use with is.  When I add this to my RP camara it wants to continually try to focus.  Why is this?  

I have been discouraged with this and 9 times out of 10 just put it back on the shelf and use my 80D.  Any help or suggestions would be greatly appreciated.  Thank you.

[deebatman316]

The RF 24-105mm F/4-7.1 IS STM lens is a variable aperture lens. The more you zoom in the less light enters the camera. Your lens and camera are working correctly. The lens you're using on your EOS 80D is a constant aperture lens. Meaning it maintains the same wide open aperture throughout the entire zoom range. For instance F/4 is wide open for lens. I don't know what lens you're using on that camera. I'm just using an example in my post. Mirrorless cameras track all the time so the AF motor is always active the same goes for IS (Image Stabilization) if the lens has it. Note using EF-S or RF-S lenses will result in the camera recording a lower megapixel image. This is due to the lens projecting an image circle smaller than the sensor. This results in the camera providing 10 megapixel images instead of 26 megapixels.

[DHenry]

So even if I have it in manual mode and set it to a certain aperture to maintain, it is supposed to change on the RP camera?  I thought the purpose of manual mode was to be able to set the settings you want and for them to not change?  I am still learning... 

My 80 D camera I tend to use my 70 - 300 ef  ultrasonic lens with image stabilizer.  When I use the adaptor to add this to the RP it continuously zooms in and out and make it hard to use.  But that is normal as well?  I'm a little confused.  Again, still learning.  

[deebatman316]

All lenses act this way on mirrorless will constantly focus and IS will always be active. All variable aperture lenses change apertures when zoomed in or out. Unless you set to something smaller than what wide open is. All versions of the 70-300mm are variable aperture and work this way too. You probably haven't noticed.

[DHenry]

Thank you.