PDA

View Full Version : enlarging distortion


Rogelio
08-25-2002, 04:03 AM
Is there a way in photoshop to enlarge things without any distortion?

vizion
08-25-2002, 05:34 AM
well, no. There will always be some distortion simply because it's a pixel pushin program. ;)

Rogelio
08-25-2002, 08:55 AM
:hmm: so there is no way to enlarge without distortion.
So how do they do multiple resolution wallpaper?

Malameel
08-25-2002, 06:08 PM
Create the large one first and then create smaller ones by just scaling it down.

izzylong
09-10-2002, 08:58 PM
Currently, raster art cannot do reverse-bicubic resampling to kill the up-sampling artifacts.

Your best bet is to print it out, then re-scan it back into PS at a higher res.

Descreen, unsharpMask, and you are good to go:)

Rogelio
09-11-2002, 04:53 AM
Originally posted by ragecgi
Currently, raster art cannot do reverse-bicubic resampling to kill the up-sampling artifacts.

Your best bet is to print it out, then re-scan it back into PS at a higher res.

Descreen, unsharpMask, and you are good to go:)


I didn't understand the first sentence:p

But the rest helps me alot you are a life saver, thanks man!

:thumbsup:

Marcel
09-11-2002, 08:30 AM
> Your best bet is to print it out, then re-scan it back into PS at a > higher res.

Oh yeah, that's a great idea! That way you loose quality twice! Once when printing, and again when scanning.

If it is a photo or image you want to enlarge to poster size, use the following method:

add 3-5 % noise
Fade noise to 'lighten'
Enlarge 30%

repeat until the image is large enough for your needs.

This way you end up with a noise with a 'photographic' feel to it. The 'fade to lighten' step is to keep the noise out of the lighter parts of the image.

izzylong
09-11-2002, 12:10 PM
Originally posted by Marcel
> Your best bet is to print it out, then re-scan it back into PS at a > higher res.
Oh yeah, that's a great idea! That way you loose quality twice! Once when printing, and again when scanning.

Look, I agree with you, but first, you gotta loose the attitude.
He never said what his original image res is set at currently.

If you've got a 720x486 D1 image at 72 dpi, and you just want to make a desktop wallpaper at 1024x768, then yes, use Marcel's tip.
But if you want your image at poster size, and you're worried about detail, the LAST thing you would want to do is ADD more noise.
You'll get some noise from the scanning process, and as long as you don't use a simple flatbed, the noise level is negligable.
A simple descreen, unsharp-mask (or preferably a high-pass layer), and it's fine:)

frog
09-11-2002, 12:42 PM
Erm, there's no doubt that the printing/scanning route is going to degrade quality substantially... And it can't introduce any extra detail or sharpness so to be honest I can't really see the benefits.

The best way is to increase the file in steps, I usually do it 10% at a time in Photoshop until I get to the required size. You are going to lose some sharpness, so you will probably need to use unsharp mask afterwards.

Depending on the type of image you are enlarging you can blow up quite a bit. 3d renders have no noise and are usually very sharp, with the method outlined above you can comfortably enlarge 200% this way and still get acceptable results. Photos however already suffer from grain and can be soft depending on how they were taken and the equipment used, so your mileage will vary a lot more with them, but a sharp photo on fine grained slide film (and scanned well) should be ok to at least 150%.

Digital means are always going to yield better results than introducing anolog equipment such as scanners & printers in the equation. However good a printer/scanner you use you are introducing too many uncontrollable factors.

Per-Anders
09-11-2002, 07:27 PM
for full on posters (advertising billboards) the traditional method isn't to create a photoshop file large enough for the poster... instead it's to get your image, photoshop or not, enlarge it using a projector. this method gets remarkably good results from really not that great footage. not to mention it allows artists to produce funky work without being slowed down by working on a file that would be several gigabytes otherwise.

this is just the way it's done.

so please don't flame me and tell me that this would create too much noise, a blurry image or anything else... it's just what people do, and i think it's worth knowing and bearing in mind if you're producing something at a really high res. it's also pertinent to the printing out and scanning in method. simple put the reason that works ok is that it gives a more organic noise to the image. sure you will always loose information with every single thing you do to an image, but each method may be more or less accepteable to the end user as each method introduces an effect to the image, so try them all out.

another method you can use is to blur the colour channels very slightly and keep the black channel more sharp. which can give you a little leaway and trick the eye sometimes, but again it does give an effect which isn't always desireable.

no matter what way you do it, you will be trying to spread out what information you do have that little bit thinner :(

another filter you may find useful while scalling up is the median filter. good for linework, especially if used in conjunction with a little noise and the tiniest ammount of blurring first you can smooth out lines reasonably well this way.

izzylong
09-11-2002, 08:31 PM
Originally posted by mdme_sadie
each method may be more or less accepteable to the end user as each method introduces an effect to the image, so try them all out.
My point exactly.
I've been using my method, and others, for my roadside billboard clients for 10 years without problems.

I think sadie hit it on the head by saying you have more than one option, try them all and find your comfort zone.

Good luck:)

Marcel
09-12-2002, 08:50 AM
for full on posters (advertising billboards) the traditional method isn't to create a photoshop file large enough for the poster... instead it's to get your image, photoshop or not, enlarge it using a projector. this method gets remarkably good results from really not that great footage. not to mention it allows artists to produce funky work without being slowed down by working on a file that would be several gigabytes otherwise.

That's a somewhat different scenario. First of all, you are using a projector (better quality than printers), secondly you are creating the end result, you are not rescanning it again for further use in Photoshop or on the computer.

Billboards and posters usually do not use images that are of 304 dpi resolution. For a huge billboard you can easily use an image with a resolution of 34 dpi (10%) als long as the linework is vertor based. Allmost always, an A3 image at 304 can be used for any purpose. You never need a file of several gigabytes.
Nobody is gonna see your billboard from 2 metres away (else why would it be so large?) so nobody will notice the lack of detail.

But if you want your image at poster size, and you're worried about detail, the LAST thing you would want to do is ADD more noise.

Of the contrary, you HAVE to add noise else you will have horrifying banding effects in color gradients (like a blue sky). Noise is good, without the noise a photo at 400% will look like an image blowup using Photoshop only, with noise it will look more like a photographicly enlarged image.

it's also pertinent to the printing out and scanning in method. simple put the reason that works ok is that it gives a more organic noise to the image.

Exactly, organic noise. Enlarging in steps and adding some noise between every step will give you exactly the same organic noise you need. If you are lazy you can also buy a filter-plugin that adds such a photographic noise with a single click afterwards (I think it's from Alienbrain).

You'll get some noise from the scanning process, and as long as you don't use a simple flatbed, the noise level is negligable.

Printing it will seriously screw the quality of the image, and it will also screw the color. Same with scanning it again. No printer-scanner combination can be better in enlarging an image than photoshop (I'm not even talking about the time it take to use your method).

My first post might contain a bit too much sarcasm, but that's because in my view your suggested method is utter nonsense. I don't want people who are new to Photoshop believing that they should print out their artwork on their HP colorjet and rescan it with their 40$ flatbed Yoko flatbed scanner, just to enlarge it. They will have much better results pressing CTRL-T.

Since you seem very confident about your method, maybe you can take a little time to prove it works better than the Photoshop method. Here is the original image:

http://members.rott.chello.nl/mvijfwinkel/original.jpg

Here is my result . (plain enlargement, and in steps with noise)

http://members.rott.chello.nl/mvijfwinkel/noise.jpg

The right image looks a bit noisy, but remember when it will be printed it will be 4 times smaller so the noise won't be as distracting (and the printing process will also soften up the noise a bit).

I'm very curious if your method will produce better results.

Edit: I would also like to know what type of equipment (brand and model for example) you use for the printing and scanning process.

halo
09-12-2002, 11:43 AM
ok i just gotta jump in this one...i can't believe what i'm reading here...time to dispel a few myths...and if your wondering how "pros" do it, i've been a profesional digital illustrator for 10 years....anyway with that said here goes...(working backwards)

1) VECTOR SPLINE BASE ART DOES NOT HAVE ANY RESOLUTION - its simply rasterised by the outout device when its printed to the resolution of the output device...if you are using purely spline/vector artwork then forget about resolution (except in certian circumstances when dealing with reduced colour range output and gradients)

2) NOISE (unless desired asthetically) is only necessary for reducing banding when dealing with gradients that lack the colour range of the colour space you are using ie CYMK

3) NEVER EVER PRINT THEN SCAN OR PROJECT TO ENLARGE - keep the image in the program and use the tools of the app like Marcel says...
Dont embed the image in another app (like flash) cos you believe it will blow the image up....its likely it will use less clever methods than photoshop anyway...and nothing can blow up raster images perfectly...even Fractal plugins...Fractals are only sometimes used if the image output show artifacts, but noise methods are also good at removing them

4)IF YOU NEED A LARGE IMAGE - the best route is to start off with creating the image to the correct size in the first place! doh!

- "How do i know how big an image should be?" Rule of thumb for output is to double the Line Screen value (mags are generally 125-175lpi so 250dpi to 350dpi is fine), if the device doesnt have a screen (transparencys, web, lambda) then use the devices highst output resolution (ie for web 72 dpi etc)...you can drop these values down 75% (ie 300 to 225 dpi) and still retain a reasonable quality but if the image contains text or fine detail then keep it to the maximum.

Various printing outputs have different screen values, magazines as i said are between 125-175lpi needing 250-350dpi (the value in photoshop) images....billboards can have screen values as low as 45lpi (go up close to one and the dots are huge) so they can only need 90dpi files...48 sheet billboard files in cymk are about 150mb+, 96 sheet 300mb+....smaller format posters can vary, but if your in doubt then aim for an image 8000 pixels large and this should suffice as this is the common size that 10x8 inch transparencies are made from (which is how it was done before digital artwork)...you can of course always have more resolution than this if necessary, it wont do any harm...
IF you do find yourself short by say 35% of the image size you need then with posters you have to remember no-one will ever be able to view the image closer than a foot away (cos it wont fit in your view) so slight little imperfections will never be seen by the target audience...so if the print insists on a 300dpi image and yours is 225dpi at the target then just blow it up...

-"My machine can't handle large files" Thats why workstations in the industry often carry 100's -1000's of mb's of ram, have huge fast hardrives for when ram runs out, and fast processors - helps with gaming after work ;)

5) RGB or CYMK? - light exposure based outputs (monitors, transparencies, lambdas) use RGB files. Anything printed normally needs CYMK files, NO EXCEPTIONS. Yes the file size is bigger, yes there are less colours but whats the point of a client approving a bright green frog on his email, if the green cant be reproduced on his printed ad? Work in CYMK preview to get a better idea of what your image will look like, TIP - bright RGB colours often look better if they are desaturated before converting to CYMK, they hold more tonal range. Yes you will get banding, but dial in a little noise to help this, values of 2-5% are unnoticable in reprodution.

There are a lot of muppets in the industry who still blow things up 300% (i have had it done to some mag front covers) or use a 72 dpi low res image cos they have lost the high res version....they either dont care about the image or are blind to the effects
take pride with your work....dont be one of them.....

this is not meant to knock anyones nose outta joint, just to inform...hope it does :D

piajartist
09-21-2002, 06:19 AM
i hope you understood the last guys intructions, they are supported though, the main thing that doesnt usually work which depends on the pixel enlargement increase. You can try going to File>Fit Image, but it depends.

CGTalk Moderation
01-13-2006, 02:00 PM
This thread has been automatically closed as it remained inactive for 12 months. If you wish to continue the discussion, please create a new thread in the appropriate forum.