John Francis

[John Francis]

Perhaps someone can help me. I start out with a 20MB image  file and when I go to Export > Save> jpeg 100% quality  the " Calculating file size" typically indicates 10 MB. I haven't cropped the image or applied any destructive editing and  I'm working in Photo Persona. To double check, I opened a 21MB  Raw file,  applied zero editing and when I went to Export > Save, the  " Calculating file size" indicates 

about 10MB.  When I actually save it and examine the file size in Apple's Preview it confirms this reduced size of 10MB. This has only just started occurring. When I had a look at some edited and saved jpegs from a few days ago they are mostly  18MB - 30MB which is what I would  expect.  Would anyone know the possible source of the problem? Thanks.

 

[HVDB Photography]

Was quality set 100% ?

 

 

O, I see, yes it was; Sorry

Edited October 26, 2018 by HVDB Photography
I see, yes it was; Sorry

[stokerg]

Hi John,

Can you upload one of the RAW files so i can do some testing? Also, on the export dialog, if you click on More, what settings are enabled here?

I've just tried this with a RAW file from my camera, which started off as 27.4MB and with zero editing, the exported JPG was 19MB, which is what i would expect.

 

[John Francis]

Thanks for  your comments. As I mentioned, I was saving the images at 100% jpeg with no destructive editing and the "calculating file size" indicated about 9 to 10 MB. When I exported/saved them and looked at them in Apple's Preview it confirmed  file sizes of 9 to 10 MB. I even checked this by putting another image through Affinity Photo and doing NO EDITING to it and then,  - Export - Save - 100% jpeg and it still gave me a "calculating file size" of 10 MB.   Later on I tried the same thing with another RAW file and "calculating file size" indicated the usual 21MB. I only tend to lose half the file size if  I have cropped a photo. I think it might be an intermitent  bug of some kind. If anyone else has had a similar problem please let me know. Thanks alot.

[kaffeeundsalz]

Which is weird because you might reasonably expect that the selected resampling algorithm would only affect the exported image if there's some actual resampling involved. 

[lepr]

.

[R C-R]

On 10/26/2018 at 7:10 PM, John Francis said:

I think it might be an intermitent  bug of some kind.

Why? JPEG files, even at 100% quality, use a lossy compression algorithm specifically designed to reduce file size. If the exported jpegs were not smaller than the originals, that would be a bug!

The details of how lossy JPEG compression works are a bit complicated but this article explains all you need to know about that.