JPEG Question

[Brian Robison]

I have some one sending me HUGE jpeg files to laser but they are at 300 dpi. These pictures are 15077 x 19139 and 8582 kb. Is there a way to reduce the picture size and get a better than 300dpi resolution?

Thanks

[Joe Pelonio]

Is your question based on the download time, or time to send from the computer to the laser? A jpg file loses resolution every time it's saved.
If you want a truly high resolution file then a tif is much better. The problem
is that tifs are even larger files.

Not as often with laser work but more so with large format digital printing, I'll require that either the customer send me an original photo that I can scan, or the file on CD or DVD. For most of my laser work 300 dpi scans are satisfactory, and come from graphic designers who have the software (like photoshop) that will allow them to size it at the actual size to be engraved at the same resolution at less than 1MB.

[Brian Robison]

Hi Joe, thanks for your responce. I need something really good for the laser. Lots of greyscale in these photos. I'd love to have them in a vector format but he already has around 100,000 of these jpegs and he's not going to change them. Shame really, they were all drawn Photshop and could have been saved in a vector format.
I guess I just resize them when I get them and go from there.

[Bill Cunningham]

Once you work on them, remember to 'never' re-save them as a .jpg
use .tif

[Tom Henry]

hmmm.. As someone who worked in photoshop on a daily basis it is known that if you reduce the amount of pixels you lose quality. I used to deal with everything from billboards to very high end magazines. Tell me what you need and I will tell you if you can achieve it.

As far as jpeg goes... we NEVER saved out as jpeg. If you want to save a file and want to compress it which you really shouldn't do if you are concerned with quality, we used to use the .eps format and in the compression section choose which one you want. Even then you lose quality.

You can PM me and I can help you out if you would like.

[Lee DeRaud]

Doesn't PNG have a lossless compression option?

[Brian Robison]

This potential customer has around 100,000 jpegs already saved and of course he's not going to redraw them. I'm only going to get the large jpegs. They should work just fine for the laser I guess. I just tend to be a little picky when it comes to quality. I need to take these huge jegs and save them as something more usable. If I import them directly into Corel the files will be so large that it will take several minutes to process. So, size and type of files to use would be helpful. Something that works well with Corel 12.

[Bill Cunningham]

I would assume that you will not be using them in the huge size provided (15077 x 19139 pixels= 50" x 60" @ 300ppi) Unless you are reproducing photographic posters, I would resample them to the size you require for the final work, and save them as a greyscale .tif file.. , a smaller physical size = smaller file.. If you use .tif compression, it will not compromise the quality of the file, because it compresses using an alogorythm.. .jpg's reduce file size by actually 'removing' parts of the file, never to be recovered..

[Aaron Koehl]

I've had great luck with .PNGs

[Brian Robison]

How do you know what size to make it? I'd like it 18" x 12"

[Tom Henry]

What resolution are you trying to achieve?

[Bill Cunningham]

How do you know what size to make it? I'd like it 18" x 12"

If your working in corel draw, from the bar at the top, select Bitmaps, resample, and you will see where you can enter the size you would like it to be, and below is the current dpi. don't change the dpi, and make sure you have a check mark beside 'maintain aspect ratio' and then click OK You may not get exactly 18 x 12 because you 'have' to maintain that aspect ratio, or things will get weird..

In photopaint, click image on the top bar, click resample, and you get the same little box to enter your changes...

[Brian Robison]

I think that aswers my question. It now says my dpi is almost 1800! Sorry I had such a hard time explaining it.
I should be able to import the 300 dpi huge jpeg and shrink it down. Change the dpi to around 600 and be happy! Thanks.

That took my file size down from 51 mb to 7, yipee!

[Rodne Gold]

All you have to to is resize the file , FORGET dpi , think PIXELS . To get the size you need resize the file to the size it's gonna be engraved at 300 pixels per inch , anything more is a total waste and even that is overkill for a laser , you can get away with 200 Pixels per inch. The laser cannot resolve more than 100 pixels per inch anyway.
Saving as a JPEG is fine for lasering , there is almost zilch quality loss and even if there is , your output device is a gross printer at best. No one barring pro stock agancies or the top of the range mags etc , want stuff like tiffs - unwieldy unmanegable files.
I don't possibly know what your customer was thinking or how he got those files or what he can possibly do with them , my Canon 5d Camera is a 12 mpix (3000 pixels x 4000 pixels) camera and its good enough for any pro to shoot with and even the top medium format digital pictures are 40 mpix , round 6000 x 6000 pixels and even with my 12 mpix cam , I can print the pic as big as I want up to ANY billboard size.(I have large format printers and do so regularily)

[Bill Cunningham]

I don't know if X3 renders files differently than 12, but you can 'think' in pixels all you want, corel resampler only specifies dpi even if your page is set-up as ppi. so unfortunately, your are 'forced' to think the way your software works or at least depicts the changes.. .jpg's are web files! Saving working files in a substandard format like .jpg makes no sense other than for use on the web.. Memory is cheap, the average dvd will hold hundreds of 7 meg files, the average h.d will hold thousands, and the processor speeds today, make the loading time of a large file pretty well insignificant.. If you are etching or engraving from a .jpg (or any other greyscale for that matter) you are going to get halftones, even the areas which look solid black are going to have 'fuzz' around the edges. For a proper job, they must be true black and white (there is no such thing as a line art or black and white .jpg) and in most cases they must be converted and dithered, or use photograv, to render your greyscale files. If your using photograv you must use bmp's which are considerably larger than .tif and converting from a saved .jpg to a bmp eliminates any storage memory savings you gain by using the substandard format.. .jpgs should only be used where they belong, on the web..