Looking for technical CC

[KmH]

Keith, it does have that little on the side of the mount... I guess I don't really understand what it does either because whenever I push it, it just seems to make the picture darker through the viewfinder...

The picture gets darker because the DOF preview button stops the lens down to the aperture you have chosen, so you can see the DOF that will be rendered in the photo. As endozm pointed out, the camera always focuses and meters with the lens wide open and doesn't set the lens to the selected aperture value until the shutter button is pressed.

I guess you've never wondered what the camera actually does when you press the shutter button all the way. If you don't understand how your tools work, you can not use them effectively. If you do not know what features the camera has, and what they do, you can't use them to help you make better photographs.

If you have an auto focus mode selected, the first thing it does is focus. Do you know how the camera does that? You've seen that mirror in the camera when you change a lens? Did you know it is only 50% reflective, because there is a smaller mirror behind it that deflects the scene the lens sees down to the auto focus module in the bottom of the camera body? That's part of the reason the viewfinder gets so dark when the DOF Preview button is pressed. only 1/2 the light hitting the main mirror gets reflected up to the viewfinder. Before auto focus, the main mirror was 100% reflective, because it didn't have a second smaller mirror behind it.

Assuming focus priority is set in the camera, once focus is achieved the main mirror swings up out of the light path. The mirror bounces a bit so the camera has to wait a short time for it to settle before it can open the shutter. While it's waiting for the mirror to get up and settle the camera sets the lens aperture.

Then the camera releases the front/first shutter curtain. If your camera is set to a shutter speed faster than 1/200 (the flash x-sync speed), the camera releases the rear/second shutter curtain before the front shutter curtain has fully opened meaning the entire image sensor is not exposed to the light from the lens at the same time. The gap between the 2 shutter curtains is just a slit. The faster the shutter speed, the narrower the slit. At shutter speed at or slower than 1/200 the front curtain opens fully before the rear curtain starts to close the shutter.

Now that the exposure has been made, a lot of mechanical action happens concurrently so the camera will be ready to make another exposure:

• both shutter curtains move back to the top of the shutter opening
• the main and secondary mirrors return to their not-making-a-photo position
• the lens aperture returns to wide open

While all the mechanical action is happening the electronics read the voltage recored at each pixel, each voltage gets sent through the appropriate part of the amplifier circuits defined by the ISO setting (a high ISO setting requires amplifying the voltage more than a low ISO setting does).
Then the amplified voltages get sent to the A-D converter converted to be changed to a digital value. If Raw is the capture choice, a JPEG Basic is made and embedded in the Raw file before the Raw image data is then written to the memory card. If JPEG is selected the digital data has to be de-mosaiced, and the file size reduced by making substantial changes to the color data the image sensor captured (up to 80% of the image color data is simply discarded by the expedient of making 64 pixel squares, the Minimum Coded Unit of color in the photo if JPEG Large, Fine is selected.) Camera maker crude and global JPEG edit presets are then applied to the photo before it is written to the memory card. Of course if Raw + JPEG is selected both processes are done.