Reducing image size and resampling makes image objectively darker

[#1]

Sometimes, when I reduce the size of an image in PS, it gets darker - both visibly and confirmed by the data in the Info Window.

Here is an example:

The first image is 16 x 40 inches at 240 ppi      (3840x9600 px).

I wanted to make a smaller print at a higher resolution so I reduced it using Image Size. Resampling was on and I chose Bicubic Sharper (Reduction) as the resampling method.

I set the new size at 8x20 at 360 ppi (which gave me a smaller image that is 2880x7200 px). 

The cursor is on the same point of the very front of the canoe in both images, but the Info Window shows different values ... and the image looks much darker on screen.

I have repeated this multiple times, restarted PS, etc with the same result.

Does this make any sense to anybody? 

Thanks for any help. 

First image (before reduction):

[#2]

Sometimes, when I reduce the size of an image in PS, it gets darker - both visibly and confirmed by the data in the Info Window.

Here is an example:

The first image is 16 x 40 inches at 240 ppi      (3840x9600 px).

I wanted to make a smaller print at a higher resolution so I reduced it using Image Size. Resampling was on and I chose Bicubic Sharper (Reduction) as the resampling method.

I set the new size at 8x20 at 360 ppi (which gave me a smaller image that is 2880x7200 px). 

The cursor is on the same point of the very front of the canoe in both images, but the Info Window shows different values ... and the image looks much darker on screen.

I have repeated this multiple times, restarted PS, etc with the same result.

Does this make any sense to anybody? 

Thanks for any help. 

First image (before reduction):

[#3]

That should not  happen try resetting your preferences. If It still works like that.  Do not resample just set the Print resolution to 480 or the with to 8"  with Resample not checked. Not a single pixel will change. The image ant image file will remain the same size. Only the print size will change from 16X40 to 8x20 You printer should have no problem printing  480PPI pixels.

[#4]

Probably a combination of color sampler precision (point sample, 3x3, 5x5...), image noise, and resampling.

On screen zoom ratio probably plays a part as well. I would assume that the color sampler works on the screen-sized cached image, just like adjustment and blending previews.

[#5]

Its all of that a resample image is a new image. All new pixels its a different image  with a different number of pixels.  The connets of the two images look simular.  They do not share any pixels and the smaller imags has less image detail.  I only resample for the web where resolutiom is meaningless all that counts is the number of Pixels.

[#6]

I wondered about that too - whether the two sample points I chose were exactly the same. But the image LOOKS visibly darker overall as well. I have been trying to get my printer to match what I see on the screen. I just finished calibrating with Syder5 Pro, and am looking into a custom ICC profile for my papers. But this adds a whole other variable. Now I'm not sure which "version" of the screen image to use for soft-proofing and printing. 

Just to confirm - both of you are saying this should not happen. Some pixels should be "thrown out" when down-sampling but the overall values/colors, etc are not supposed to change - correct? 

[#7]

Yes and no. If there is a fair bit of noise in the original image, resampling could change the overall tonality. Just think of finely hatched engravings - downsampling can easily block it up and kill the "air". Or a starry night.

Ultimately I couldn't say without having the full image in front of me.

Generally, to make reliable judgements about this you have to view at 100% - one image pixel represented by exactly one screen pixel.

[#8]

Pixels are not thrown out detail is.  Some interpolation algorithms generating a new image from the current images pixels.  The image do not have pixel in common they are different size images. With fewer pixels you have few details.  Like you have less details is a Classic comic then you  have in the Classic novel. However the story are the same. Resizing Image is similar like that they are different interpretation renderings of a scene.

The detail you sample in the large image may not even exist in the resized image.