For black and white images in technical manuals, which format do you prefer?

[FernandoRocker]

So, I'm new at this company, and the person who is training me uses the EMF format for the images on the manuals.

Do you think a PNG file would be a better option for illustrations?

[Bob_Niland]

What platform (OS)?
What Frame version?

What illustration tools (Adobe Illustrator, for example)?

By B&W do you mean bit-tone (only pure white or black elements), or grayscale?

Do the images originate as raster or vector?

What is the delivery format (paper, PDF, HTML, ebook)?

[FieryPantone]

Sensible questions have already been raised; my first comment would be, not .emf  My general preference has always been for a vector format such as .eps or .svg for line-drawings; for example, neat drawing of product to be adorned with call-outs. For screenshots, which almost always have to be tweaked, I use .png – don't know whether your reference to b/w means original illustrations in b/w or full-colour illustrations published in b/w.  You'll probably get more detailed answers once you've filled us in on the context of your question.

[FernandoRocker]

Sorry about the lack of info.

We do technical manuals for the equipment we sell. 90% of the manuals are digital (burned into a CD) and 10% are printed in grayscale.

We are using FrameMaker for the writing and layout and Illustrator to draw some of the techical illustrations (vectors, using only black and white lines and shapes). We then proceed to export the illustrations to EMF and then we import them into FrameMaker.

For raster images, they use JPG.

But I think both formats (EMF and JPG) are not optimized at all for the process.

What do you think?

PS:

OS: Windows 7

FrameMaker: 11

[Bob_Niland · Accepted solution]

> ... 90% of the manuals are digital (burned into a CD)

Presumably as PDFs, which the ends users then either view on line or print locally?

> ... and 10% are printed in grayscale.

On what type of press?

You probably want the images optimized for on-line viewing.

In the case of line art, this means staying in vector form, so that it scales cleanly, and using a stroke weight that is optimized for typical resolutions and convenience printing.

In the case of raster art, this means having enough resolution to maintain detail at reasonable zoom, and on convenience printers.

For vector, we normalize stroke weights to about 0.2 point, save as EPS and import the EPS. On Frame versions later than 7.x, PDF import might also be stable, and preserves vector as vector. SVG I haven't tested.

For raster contone (grayscale or color), avoid JPEG in the workflow. It is lossy and introduces artifacts. Never use it for screen shots or scans. Even if your camera image is JPG, convert it to an uncompressed form during edit and post-processing, such as PSD. Our target delivery resolution for contone is 200 dpi. This is slightly more than our press can resolve, but provides a bit of zoom for PDF viewing. We save the final images as EPS, and import those. TIF is also OK for this application (uncompressed). We select the compression level during PDF generation.

For bitmap images, again avoid JPG. We optimize these for 600 dpi (our press resolution), save and import them as TIF (EPS is really clumsy for bitmap).

EPS is a bit annoying to work with in Frame, as what you see during edit is a thumbnail or preview (72 dpi), but what renders to Ps or PDF is original vector or full raster. But EPS is fast, rock solid, and (if you need it) can preserve original CMYK color into the Ps or PDF.

[FernandoRocker]

Thanks!

Your response was perfect. Now I have to write an e-mail to my boss explaining all that to him!

[FernandoRocker]

Yes. We save the files in PDF.

The printing is done in a laser printer.

[Bob_Niland]

Another matter to consider is the transfer characteristic (grayscale tracking) for contone images, to avoid washed-out or muddy images.

We use sRGB color space for color images, which has a sort-of 2.2 gamma (it's discontinous near black), so we also elect Gray Gamma 2.2 for grayscale.

Frame has no color management to speak of, so we elect "Tag All Images for Color Management" during PDF render, specifying sRGB for color and GG2.2 for gray..

You need to test some PDFs, on representative printers, to ensure that what you and your users print roughly matches what's seen on screen.

[Bob_Niland]

> ... EPS is a bit annoying to work with in Frame, as what you see during edit is a thumbnail or preview (72 dpi) ...

And grainy or blocky indexed color as well.

This probably applies to PDF import also.

There are a couple of tricks that can be used to deal with the "coarse preview" annoyance.

One is to render multiple formats of the original art, such as EPS and TIFF. Import the TIFF for precise work (like callout placement), then replace the image with the EPS when done.

Another is to scale the EPS in the image editor (such as Illustrator), to, say, 400% or more (scaling strokes and effects). When importing into Frame, scale it to the reciprocal (25% or less) after import. In the case of 400% / 25% this makes the preview 4x sharper.

There are some caveats with this scaling hack:

1. There are size limits on both the image import into Frame, and creation of the Preview/Thumbnail in the EPS itself. You normally run into the preview limit first, but rarely at 400%.
2. PDF size: You will want to be subsampling raster contone images during PDF render, and at least LZH/ZIP compressing bitmaps (if you use EPS for those), otherwise your 400% EPS raster images will have 4x the res they need, at the expense of file size.
3. Meta-clutter: Preview and thumbnail images are metadata in the EPS, which Frame unfortunately preserves into the Ps or PDF output. They can represent a LOT of MBytes, particularly if you're using the 400% trick. You need to redact Metadata* in Acrobat Pro (Examine Document tool). This, alas, also redacts your PDFinfo, but you can paste that back in.

________

* Your camera EXIF info is also metadata, which can also easily survive into the PDF, especially if you import JPG. It's not much data, but it can advertise to the world: your camera model and serial number, photo data, photo GPS location, etc.

[Arnis_Gubins]

@Error,

FYI, the preview image in an EPS file can be any resolution. The 72dpi is typically a default setting in many applications, but some apps allow you to specify a resolution or add your own version of the preview image. Saving PDFs as EPS provide much higher resolution preview images (in 8-bit colour too), which are more optimal to work with in FM (since FM has to do an internal conversion of PDFs to EPS anyway).

[Bob_Niland]

> ... the preview image in an EPS file can be any resolution.

Thanks, I didn't know that, having never seen anything else.

> ... some apps allow you to specify a resolution or add your own version of the preview image.

Would Illustrator (CS5 here) be one of them?

I don't see anything in the Edit > Preferences

or File > Save As > EPS

perhaps buried in a .ini file that I can't find?

[Arnis_Gubins]

Unfortunately AI only allows you to specify B&W or 8-bit colour (transparent or opaque; use opaque for FM, the transparency choked earlier versions of FM - haven't tried it in FM11).

Older tools such as Quite's PSAlter or TechPool's Transverter Pro allowed the saving/merging of custom previews.

Corel Draw has a much nicer interface for saving as EPS. It allows setting of the dpi and many other options that AI doesn't. I've always preferred Draw to AI.