100MB+ Resize to 1MB

[Zack871024]

I have multiple 100 MB+ psd and tiff files in CMYK. I would like to resize them into 1 MB, 300 ppi and around 10-15 cm in width.

I tried doing it through image size and re-sampling. But the smallest file size I could get is around 3.9 MB.

Strangely, if I put the exported 3.9 MB jpg onto a new canvas, and do the export again, the file size could be lowed to around 900KB.

Is there any quicker way of doing this kind of resizing? Or this is the only way?

Thanks

[c.pfaffenbichler]

What is the »end-game« here?

Why CMYK and which Colour Space exactly?

What file format do you save to?

Is there significant Ancestor metadata involved?

Have you tried using File > Export > Save for Web (Legacy) to resize, convert to sRGB and remove metadata in one go?

[Zack871024]

The reason I specify CMYK is because if you save it for web the color space will be converted to RGB. I need these file to be used in print, that is why I need it in CMYK and with 300 ppi. The file format I have to save to is JPG.

[c.pfaffenbichler]

Is there significant Ancestor metadata involved?

[Zack871024]

Nope there are not. I checked it with XMP in photoshop.

[c.pfaffenbichler]

Can you provide one of the files?

[Zack871024]

I am really sorry, I wish I could that would be a lot easier. Unfortunately, I can not send out my client's files.

The image was taken by a Phase One IQ180 at 6179x5672 @ 1355.73 Pixel/Inch btw.

[G_Hoffmann]

An embedded CMYK profile would consume 1.5...2.5 MByte,

e.g. 1.74 MByte for ISOCoated-v2-eci.

The embedded profile will be part of the image file (PSD, TIFF,

JPEG), it is not added as Metadata by XMP.

The JPEG compression for RGB images is based on splitting

RGB into YCbCr, where Y is the Lightness and Cb,Cr are residual

colors (comparable to a and b in Lab).

The numerical compression loss for Y is low, but very high for Cb,Cr.

One reason is the so-called subsampling, where Cb (and Cr) for

each group of 4 pixels is considered as one value. This CbCr com-

pression doesn't affect the visual quality very much.

But CMYK cannot be split into Y and residual colors, because this

would destroy the black generation. Therefore each channel has

to be treated as a Grayscale image, applying the same low-loss

strategy as for Y.

Therefore the filesize of a CMYK JPEG is not only larger by factor

4/3 compared to RGB, but in fact much larger for the same visual

quality.

Best regards

--Gernot Hoffmann

[Mylenium]

Well, are you actually sure you are using the same settings and procedures every time? To me it sounds like you don't and that you are merely experiencing color profiles and other metadata being dropped when you re-import your files in a standard document with no custom color settings and the like. If that works, then logically all you would need to do is strip that information from your other files just as well, possibly by ways of using an action to switch the color settings around and using Save for Web/ Save as Copy or whatever.

Mylenium

[Zack871024]

Yes indeed, I use the exact same settings every time I import the jpg I exported in the first step. The new canvas I created in also 300 ppi, in CMYK.