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Can I convert to B&W in Lightroom and remove all colour data?

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houghtonphoto

houghtonphoto

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Lightroom Version Number
Lightroom Classic version: 8.4.1
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  1. macOS 10.14 Mojave
I've just released a book on street photography on Amazon Kindle Direct Publishing, but the 140 page 6"x9" book which contains 64 square format B&W images is about 46Mb, even when the PDF is optimised in Adobe Acrobat. This makes it a larger than normal Kindle download according to Amazon, who deduct royalties in proportion to how big the Kindle download is. So, if I can make the book PDF smaller I will presumably reap a bigger slice of the royalties each time the Kindle edition is downloaded.

The images have to be set to 300 dpi, so I've sized them to 1500px (300dpi x 5"). I know that in Photoshop you can save an image and tell it to discard all colour data which reduces the file size by only keeping greyscale data, but I can't see any setting in Lightroom to achieve this?

If I can do it in Lightroom it'll save me having to export all 64 images into PhotoShop and process them - thought someone on the forum might know if this can be done?

Thanks from a sunny Dublin, Ireland

Joe Houghton
www.houghtonphoto/streets-of-dublin
 
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Lightroom is a parametric editor, which means that the original image is not touched and the edits are saved as a kind of 'To do list' in metadata. So no, you cannot discard any data of the image in Lightroom. When you export an image it gets rendered with the edits, but Lightroom will always export an RGB image even if that image is in B&W. Lightroom does not support other color models (not to be confused with color spaces). To make it a true greyscale image you will have to use Photoshop.
 
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Your PDF is neither JPEG or Color images (even if your originals may be) When LR creates the PDF, it exports edited copies of the adjusted mat to a temporary location. It then builds the PDF file. Once the PDF file is created, it discards the files in the temporary location.
AFAIK, the PDF is sized according to the data inside. This link may help you understand the PDF file format and may give you hints on how to reduce the size of the PDF. Understanding the PDF file format - How Are Images Stored
 
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Johan Elzenga said:
Lightroom is a parametric editor, which means that the original image is not touched and the edits are saved as a kind of 'To do list' in metadata. So no, you cannot discard any data of the image in Lightroom. When you export an image it gets rendered with the edits, but Lightroom will always export an RGB image even if that image is in B&W. Lightroom does not support other color models (not to be confused with color spaces). To make it a true greyscale image you will have to use Photoshop.
Click to expand...

Many thanks Cletus - this makes it quite clear. Off to Photoshop so :)
 
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300 dpi is a standard for offset printing. Other environments may require less, for example ink jet printing is OK with 240 dpi.
For PDF / Kindle I have no clue. Did you try with a lower dpi ?
Bernard
 
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Bernard said:
300 dpi is a standard for offset printing. Other environments may require less, for example ink jet printing is OK with 240 dpi.
For PDF / Kindle I have no clue. Did you try with a lower dpi ?
Bernard
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The term 300DPI is probably irrellevent in a PDF. The PDF Is going to use a RGB image of a certain pixel cimensions and fit it into an image box defined to be a certain size on the document page. The RGB image will be resized to fit the box
The PDF is a Vector file and does not have a resolution. You could print the PDF on a standard letter page or a sheet that is 17”X22”. The display software will scale the PDF.
Likewise the number of pixels in the RGB image that gets stored in the PDF file might be constrained by the PDF software and resized before being created or retained as full pixel dimensions and resized only at the time the Vector file is rendered

http://ipdfdev.com/2016/07/06/what-resolution-pdf-files/
 
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