Question

crf8 · Jan 5, 2019

My wife got me a tripod for Christmas.
I mounted my Sony 6300 on it and set to auto, scene select, closeup.
As I focused in on the wood object the camera kept changing the shutter speed, lighting was the same. Starting at 1/120 down to 1/80 as I got focused in close. Is this normal?
I prefer a speed of 1/100 or quicker, but with tripod maybe that’s not needed? Any info appreciated!

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Fujidave · Jan 5, 2019

It is because you set it to Auto. When the camera is on the tripod try it in Aperture mode and go from there as it will be on the tripod.

dxqcanada · Jan 5, 2019

You use the term "as I focused in close" ... do you actually mean as you zoomed the lens to a larger focal length to make the image of the car larger in the scene (and/or moving the camera physically closer)? If so, then the light meter is reacting to the change in overall amount light being received, as the car is reflecting more light than the background ... I would expect that in auto mode.

With a tripod you would easily shoot at lower shutter speed as it's purpose is to stabilize the camera/lens.

Overread · Jan 5, 2019

If you get a white sheet of paper and a grey one and set your camera up on tripod and place each sheet before the camera to focus on you will find that, even in the same lighting, the exposure will be different.

The camera meters (reads) light based upon what is reflected off the subject and into the lens (or is direct from the light source if you aim the camera at a light source). Depending on the metering mode the camera will read light from different areas, spot mode would mean that it would read light only from the middle* dot of the camera; whilst many other modes read light from around the scene (centre weighted is often popular as that reads all the light, but has a bias toward the area in the middle*.

So as you focused the camera the scene content might have shifted a little, which means the camera was adjsuting for the variation in light falling on it.

Sometimes the light is also really on a knife edge so even tiny shifts in position or just resampling the scene can result in the camera giving a little variation in the exposure.

These little shifts are often not an issue for the exposure, though they can be annoying at times. If you've got fixed light and a fixed scene and subject then manual mode can be easier to work with. Plus with manual you can move your lighting around and see the effect it has on exposure. It gives you more control over the scene because the camera will take the same exposure each time until you tell it otherwise.

*On some cameras it will be the active AF point not just the middle of the camera.