Export image - changed file size

[dianah9718856]

Hi. I am not an experienced user of Photoshop but I learn every day. I run Adobe Photoshop 2017.

I try to finish my small on-line shop and I am in process of loading products. I take pictures with a NIKON DSLR in RAW format. I process them in Lightroom then I size image and export as JPG.

My Prestashop theme needs 270x270 px/inch for image size. I export as MEDIUM quality and optimized, sRGB...resolution 72, thinking a 4 kb file size (as Photoshop show in the export window) is OK for my shop.

If I load this image into my prestashop i got this surprize: the file size changes. 12-20 kb. Sometimes even 25 kb.

If I go to my shop front and save the images by "save image as" to my desktop then I check the size of the file and is 12-20 kb.

Also in the folder where I export them in my computer the images are loading at 4 Kb but after I export them, if I try to exit the Photoshop I need to save them. When I do this the size of the file is 20-25kb.

Why is that? Why I cannot keep them at the size Photoshop stated in the Export window. Why is keep changing. This is heavily affecting my shop speed.

Thank you and sorry for my English.

[Derek Cross · Accepted solution]

Crop your images as square then open them in Image > Image size and set the size to 270 x 270 px and save as a JPG and select the compression that gives you the smallest file size with the least image degradation (you judge this visually). The resolution is irrelevant in this context.

[dianah9718856]

Hi. Thank you so much for your answer. I open Image, Image size:

What I see is this:

Image size 213.6 Kb

Dimensions 270 px x 270 px

Fit to original size

Width 3,75 inch

Height 3,75 inch

Rezolution 72 pixles/inch

Resample: checked Automatic

The image is cropped square before it is exported. 270x270px with 72 resolution. Now I checked again. If I just export the image the size of the file remain OK in the computer folder. But if I try to close the Photoshop I see 2 successive windows:

1-Save changes to Adobe Photoshop ...Image before closing? I click Yes.

2-JEPG Options: Quality 10, Maximum, Format options - Baseline.

After this the saved file is going up from 4 kb t0 20 kb.

You say I must move slider left to smaller file size until from visual point of view the image looks acceptable?

Why I did not see this before? My fault.

I do have a question: Why I see in this window 213,6 Kb when I exported as 4 kb? Just as quriosity.

You help me so much. God bless you.