EOS Rebel T8i landscape vs. portrait enlargement: portrait comes out darker than landscape

[stevet1]

I ran across a phenomenon yesterday that I hadn't noticed or thought about before.

That is the apparent enlargement of photos taken in landscape or horizontal mode vs. the same picture in portrait or vertical mode. And I'm not sure why that is.

I took two pictures of a flower with a crop sensor, T8i. I was standing about five feet away from the flower and did not change position. I focused on the center of flower in both photos. I removed the possibility of zoom by using a 50mm prime lens for both. I was using a 4:3 aspect ratio for both. I was in Av mode with f9 and an ISO of 100. The horizontal photo came in at a shutter speed of 1/400. The vertical at 1/320.I took them both in jog and in RAW.

I cannot explain why the vertical picture comes out slightly darker at a slower shutter speed than the horizontal at a faster speed. I noticed that yesterday also with a different photo.

The subject (the flower) in the horizonal photo is enlarged compared to the vertical.

I tried posting the pictures here, but the forum software resizes them for its own purposes and they come out the same size, so you'll just have to try it out for yourself to see what I mean.

Steve Thomas

Steve Thomas

[NatalyaP]

Greetings stevet1,

The difference in subject size and exposure you are seeing between your horizontal and vertical shots may come down to how your camera's metering system and image software orientation work, rather than any physical change in the lens optics.

When you rotate your EOS Rebel T8i from landscape to portrait orientation, the camera's Evaluative Metering system recalculates the lighting across a completely different distribution of the scene (such as incorporating more bright sky or darker ground into different parts of the frame). In your case, the vertical orientation metered the overall scene slightly differently, resulting in a 1/320s exposure that rendered darker due to where the light falloff occurred.

Regarding the flower appearing enlarged in the horizontal photo, this is an artifact of how computer monitors and viewing software display images. Standard computer screens are horizontal (16:9 or 16:10 aspect ratio), meaning a horizontal photo can fill the wider screen space, whereas a vertical photo must be scaled down to fit the height of your display. If you crop both images to the exact same pixel dimensions in an editing program, you will find that the 50mm optical magnification of the flower itself is identical in both shots.

[LeeP]

You beat me to it. 🙂

[stevet1]

NatalyaP,

You wrote, "Regarding the flower appearing enlarged in the horizontal photo, this is an artifact of how computer monitors and viewing software display images."

It does that on the camera's LCD screen too, but I imagine the principle's the same.

So, the horizontal shot is "artificially magnified" to, as you put it, "fill the wider screen space"?

I hadn't thought about the evaluative metering gathering light from different parts of the scene based on your orientation, but that makes sense. 

Thanks.

Steve Thomas

[ebiggs1]

Metering mdoe.