File Size Discrepency from Photoshop to Lightroom

[Gabrielle Madsen]

Hi Everyone,

Yesterday I discovered that my file sizes were unable to upload from Lightroom as PNG to Adobe Stock.  (I do a lot of digital work for game engine so I just typically save for web in PNG and became a habit).  However, I also discovered that the file sizes were in the kb's rather than at least 4 MP as minimum size for Adobe Stock.  So I have since resized and resaved to JPG.  But the odd thing I discovered this morning is that after saving files as JPG they were still too small despite what appeared to be adequate sizes.  Is there a technical understanding I am missing?  Example Images Attached.

[Per Berntsen · Accepted solution]

MP (megapixels) is not file size, but the pixel count of an image.

So 4 MP means 4 million pixels. An image measuring 2000 by 2000 pixels will be exactly 4 megapixels.

The image you have at 1200 x 1800 pixels is 2.16 megapixels, and therefore smaller than what is required.

So you have to resize to pixel dimension that when multipied are over 4 million, like for instance 2000 x 3000.

[Gabrielle Madsen]

Thank you thank you!   And yes, of course

So minimum should be 2000 pixels on either side! 

Apologies for such a novice question but truly appreciated

[dj_paige]

Well, I don't really think the minimum has to be 2000 pixels on either side.

2000x2000 is indeed 4MP, but so is 1000x4000 and so is 2667*1500, and many other combinations.

[Gabrielle Madsen]

Gotcha, yes that makes sense mathematically as well.  Curiously I was confused by the image size reading 6.18 M (as this is what I believed indicated that the file was indeed over 4 M.

[Per Berntsen]

For some reason, the image size dialog in Photoshop uses M for megabytes instead of the commonly used MB, which can be confusing.

So MB = megabytes (file size), and MP = megapixels (pixel count).

[Gabrielle Madsen]

Perfect, now that makes sense! 

[Abambo]

...and just to add some stock knowledge:

files that get up-scaled are at risk of being refused just because of that reason.