What causes 300ppi photoshop file with type looking pixellated?

[claude72]

Originally Posted by toronar

If you have an unflattened version (where the text is still a text layer in Photoshop), you can save as Photoshop PDF from within Photoshop. This will keep the text as vector and it will be smooth sailing from there on.

Yes, it works... (you can also use EPS with "Keep vector text" option activated)... but I often experienced problems either with PDF or with EPS... fortunately, when one file doesn't work, generaly the second accept to do the job... if you are lucky you'll perhaps use the right one at the first attempt

The sharpness of the text is not the only problem with text in Photoshop: with saving the text as vector, using PDF or EPS, OK you'll get crisp vector text, but you will go on dealing with other problems:

• first, most of the unaware users using text in Photoshop make RVB black text that will become CMYK text, and will stay in CMYK mode in the PDF or EPS file... then you will have risks of misregistration issues...

• second, if fortunately the text is black only or if you convert all the CMYK black text in black only, as Photoshop doesn't handle neither overprinting/knock-out nor trapping, all the black text will knock-out the back colors and picture-s without any trapping: getting a perfect registration on an offset press without trapping is often more difficult than to print a CMYK black!!!
To fix this issue, you'll have to set each text layer in Photoshop in the mode "Produit".
(sorry, I dont know the translation... see the linked screen shot...)

[claude72]

Originally Posted by kyle

Nice examples.

Thanks.

When you save as a PDF from Photoshop
(...)
Instead of the text being directly rendered with a fill color, it is used as a clipping mask to reveal parts of an image.

Yes, I noticed that...

(one of the methods I use to print a vector text from my customers's Photoshop layouts is to "extract" the vector datas from an EPS or a PDF (the first one that accept to work correctly ) with illustrator and re-work it in Illustrator... and I have to first remove all the colored images giving the color to the text, then remove the clipping masks, to finally give the wanted color to the text, and make it overprint... long job, but perfect result, and no problem with offset printing!!!)

If you place black text over a regular image, Photoshop will create an image in a rectangular area that extends past the edges of the text, and all of the pixels will be black. It then uses text in a font as a clipping mask to cut out the image so that only the text is visible. This is interpreted differently than normal text by the trapping process, and I believe it will not be trapped by the Adobe trapping engine no matter the settings.

Yes... I have no information about the Adobe trapping engine, but I have the same feeling than you have...

... because I tried to use PitStop to modify the color of the text in a PDF from Photoshop (mainly to try to change CMYK black) and to make it overprint... but no way!!! when clicking on the text, PitStop shows that the text has no color... and nothing can be changed nor fixed...

... and I guess that this issue with PitStop comes from this particular structure of the text, with clipping masks cutting images, and that it also makes some fonctions of the RIP (like automatic trapping, automatic conversion of CMYK black and automatic black overprinting) being unefficient.


(and sometimes I experienced problems with the placement of the colored image behind the text, with for example the image beeing not high enough to reach the extremities of the ascent of the text... and the upper part of the text seems to be cut... or the accent are missing...)

You said that screen dots cannot be cut to follow the ideal path when the type is rasterized. I assume you mean that the screen dots cannot be cut within the domain of a pixel of the raster image, since they are cut on the edges of them.

I'm not sure to understand exactly your question... sorry, english is not my native language...

But, in fact, pixels can never be cut: each pixel is always a whole square area, even if they try to follow a circle: they will be placed along the curve, but one part of the pixel will always be outside the circle, and the result is always a kind of stair, jumping from a square to another square... and with a quality factor = 1, meaning that you use a 150 ppi picture for a 150 lpi screen, all these "not cut" pixels will be transformed in entire "not cut" screen dots and the size of the screen dot depends only:
- first of the screen ruling,
- and second of the density of the corresponding pixel...

... so if for example a pixel is exactly on the limit of the circle, meaning that half of the pixel is outside the circle and the other half is inside the circle, the corresponding screen dot can be also exactly on the limit of the circle, with one half part inside the circle, and the other half part outside the circle, altering the shape of the circle.

(with a quality factor = 2, meaning that you use a 300 ppi picture for a 150 lpi screen, each screen dot is made with 2x2 pixels... so if for example the 2 left pixels are outside the circle - and then white, and the 2 right pixels are inside the circle - and then black, the corresponding screen dot will be 50% gray, placed exactly on the limit of the circle, with its right half part inside the circle, and its left half part outside the circle, altering the shape of the circle.)


In a vector system, the screen is made "through" a clipping-mask, and the screen is "cut" exactly by the edge of the clipping-mask: so a circle is a clipping-mask, transparent inside and opaque ouside, and only the screen dots and the screen dots parts that are inside the mask are imaged, and the parts of the screen dots that are under the opaque mask are not imaged and suppressed: that's why in a vector system the screen dots are "cut" exactly to follow the shape...

(sorry, it's difficult for me to explain all that in english...)