ronh
06-17-2008, 10:41 AM
I am getting ready to prepare a photobook and am confused on three issues. I have several hundred images that were shot at 16 megapixels in RAW format, uploaded into Photoshop as ProPhoto RGB 16-bit 300 PPI (note, Photoshop is device independent and does not work in DPI, but only PPI). I have sharpened them using unsharp mask, color corrected them using levels, white-point, black-point, neutral gray-point, curves, etc. In other words they are exactly as I want them and I just have to flatten them, covert them the JPG and size them. This is there the confusion comes into play.
I've been a graphic designer for 20 years, worked in pre-press departments and teach electronic pre-press. All presses have two ratings, their DPI and LPI. The DPI (dots per inch) is the half-tone dot rating for printing fonts, vector images and one bit line art. In general presses have a DPI rating between 1200 and 2540. The photoshop formula is PPI (pixels per inch) = DPI (max 1200). Therefore, your statement of a 175 DPI is frightening because would result in extreme low resolution of the text in the book. Is 175 the true DPI of your press? You keep switching references between DPI and LPI and they're not interchangeable.
Raster images (photos) use the LPI (lines per inch) or line screen rating of the press. The photoshop formula for this is PPI = 2 time LPI. In other words a 175 LPI press prints its highest resolution when the images are 350 PPI. Yet again you state that the LPI of your press is 175 but we should only use about 200 PPI for our images. This means the true LPI of your press is only about 100 LPI or just barely above newspaper printing. I have spent several thousand dollars in taking and preparing the photos for the book and want the highest quality print. Please clarify your press LPI and DPI as well as the PPI required.
The next question has to do with the RGB color gamut. sRGB has the smallest ICC color profile range and is generally used only for newspapers and lower quality image printing. Up until a few years ago, Adobe RGB 1998 was the standard because of its greater ICC color profile range. However in the past few years, most Pro Photographers have switched to Pro Photo RGB which has a much greater ICC color profile range than Adobe RGB 1998. I really don't want to have to save my images out as Adobe RGB if I can avoid it as the loss of color would be great. My question is what CMYK ICC profile do you use? I'm hoping it's SWOP and you have the CIE L*A*B conversions from Pro Photo RBG to your output gamut.
My last confusion/concern has to do with image adjustment procedures. My greatest concern is that you are adjusting images that are already exactly as I want them. One of the most important rules in color correction is to never correct on more than one color channel at a time and you state "All adjustments are based on composite pixel values and are applied globally to all color channels, and not to specific colors". I'm hoping you can say that you can turn the image adjustment procedure off or that your process won't change the color of my images.
I really like the formats and flexibility of your books and would like to use your services, so I'm hoping you can help me with my concerns.
Thanks,
Ron
I've been a graphic designer for 20 years, worked in pre-press departments and teach electronic pre-press. All presses have two ratings, their DPI and LPI. The DPI (dots per inch) is the half-tone dot rating for printing fonts, vector images and one bit line art. In general presses have a DPI rating between 1200 and 2540. The photoshop formula is PPI (pixels per inch) = DPI (max 1200). Therefore, your statement of a 175 DPI is frightening because would result in extreme low resolution of the text in the book. Is 175 the true DPI of your press? You keep switching references between DPI and LPI and they're not interchangeable.
Raster images (photos) use the LPI (lines per inch) or line screen rating of the press. The photoshop formula for this is PPI = 2 time LPI. In other words a 175 LPI press prints its highest resolution when the images are 350 PPI. Yet again you state that the LPI of your press is 175 but we should only use about 200 PPI for our images. This means the true LPI of your press is only about 100 LPI or just barely above newspaper printing. I have spent several thousand dollars in taking and preparing the photos for the book and want the highest quality print. Please clarify your press LPI and DPI as well as the PPI required.
The next question has to do with the RGB color gamut. sRGB has the smallest ICC color profile range and is generally used only for newspapers and lower quality image printing. Up until a few years ago, Adobe RGB 1998 was the standard because of its greater ICC color profile range. However in the past few years, most Pro Photographers have switched to Pro Photo RGB which has a much greater ICC color profile range than Adobe RGB 1998. I really don't want to have to save my images out as Adobe RGB if I can avoid it as the loss of color would be great. My question is what CMYK ICC profile do you use? I'm hoping it's SWOP and you have the CIE L*A*B conversions from Pro Photo RBG to your output gamut.
My last confusion/concern has to do with image adjustment procedures. My greatest concern is that you are adjusting images that are already exactly as I want them. One of the most important rules in color correction is to never correct on more than one color channel at a time and you state "All adjustments are based on composite pixel values and are applied globally to all color channels, and not to specific colors". I'm hoping you can say that you can turn the image adjustment procedure off or that your process won't change the color of my images.
I really like the formats and flexibility of your books and would like to use your services, so I'm hoping you can help me with my concerns.
Thanks,
Ron