image size reduction

stan the man

stan the man

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mark
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hi,

i was hoping that someone could tell me how to reduce an image size down to a size that will say,have the longest edge 800 pixels and be 72 DPI?

i will also want to keep the original size.

sorry for the stupid question :bonk:
 
Not a stupid question at all Stan...

This depends on what platform you are using for your OS. If you're on a PC, you might like to try a free application called the GIMP. It's akin to Photoshop, but free, and some say performs almost equally as well as Photoshop. With that application you can resize any image to whatever size you want.

If you're on a Mac, then you can use the supplied 'Preview' app to resize an image to whatever you want.

How's that?
 
:agree: gimps great.
 
In CS3

Image > Image Size > the select your size!

Simple...
 
From the top bar click image then image size it gives you all the options you need
from ins pixels cm DPI

edit b****r too slow
 
Am I not right in thinking you can use the crop tool to resize and alter the DPI at the same time?
 
AndyB said:
Am I not right in thinking you can use the crop tool to resize and alter the DPI at the same time?
Click to expand...

Yup - that's how I'd do it

Oh jeez - are we agreeing AGAIN :eek:

Click on the Crop Tool
Type 800 px into the width
Type 72 into the resolution

And as you crop away the image will always be resized to 800 on the longest side and at 72 dpi - the height you can change as much as you like; but if you want to specify the height as well you can do

It's especially useful for us 'White roomers' as you can crop a shot by adding white space at the same time to either width or height = ace

:thumbs:

DD
 
One easy way is to use File - Automate - Fit Image
If these documents are to be used for the web PPI (Pixels Per Inch) are irrelevant. It is the pixel count that matters.
DPI (Dots Per Inch) refers to the printer not a document.
 
Paul MR said:
One easy way is to use File - Automate - Fit Image
If these documents are to be used for the web PPI (Pixels Per Inch) are irrelevant. It is the pixel count that matters.
DPI (Dots Per Inch) refers to the printer not a document.
Click to expand...
The thing is, if you save a file for printing, with say the dpi at 300, it will be a larger image in KB than an image prepared for display on a monitor - which is 72 dpi.

So, the Save-for-Web function in many image apps, actually saves the image in the correct format for display on the net.
 
theMusicMan, sorry but you haven't grasped the concept.
I did say if it was for the web. If so PPI (not dpi) is irrelevant
Pictures sent the the printer is a totaly different matter.
That is when the pixels per inch (resolution) is relevant to the printer/rip to know what size the picture should be.
Also all monitors do NOT display at 72 PPI in fact mine is 96 PPI
 
Paul MR said:
theMusicMan, sorry but you haven't grasped the concept.
I did say if it was for the web. If so PPI (not dpi) is irrelevant
Pictures sent the the printer is a totaly different matter.
That is when the pixels per inch (resolution) is relevant to the printer/rip to know what size the picture should be.
Also all monitors do NOT display at 72 PPI in fact mine is 96 PPI
Click to expand...
No need to apologise, I have grasped the concept actually.
Regardless of what you say, a file saved at 92dpi (if that is what your monitor displays at) will yield a file size smaller than one for a printer saved at 300 dpi.
 
Guys
the pixels per inch resolution - actually ppi (it's not dpi) of your image matters NOT A JOT when resizing on screen.

An 800 pixel x 600pixel image is a fixed size whether it's 1000ppi or 300ppi or 100ppi..... it's still an 800 x 600px image.

ppi ONLY matters when you come to print the image.

theMusicMan said:
No need to apologise, I have grasped the concept actually.
Regardless of what you say, a file saved at 92dpi (if that is what your monitor displays at) will yield a file size smaller than one for a printer saved at 300 dpi.
Click to expand...

So as above your comment is not Necessarily true!
 
DiddyDave said:
Yup - that's how I'd do it

Oh jeez - are we agreeing AGAIN :eek:

Click on the Crop Tool
Type 800 px into the width
Type 72 into the resolution

And as you crop away the image will always be resized to 800 on the longest side and at 72 dpi - the height you can change as much as you like; but if you want to specify the height as well you can do

It's especially useful for us 'White roomers' as you can crop a shot by adding white space at the same time to either width or height = ace

:thumbs:

DD
Click to expand...

You don't need to enter 72 ppi (not dpi) into the resolution box - see above :)

The ppi only determines the size of the final output (size of the actual print)
 
cheers guys....i've actually managed to do it :thumbs:

what i did was.....

open image in CS3
click on image tab>image size,and reduce longest size to 800(shortest size is automatically adjusted)
change resolution to 72 PPI
then click file tab>save for web..

job done!

does that sound right with you folk?
 
stan the man said:
cheers guys....i've actually managed to do it :thumbs:

what i did was.....

open image in CS3
click on image tab>image size,and reduce longest size to 800(shortest size is automatically adjusted)
change resolution to 72 PPI
then click file tab>save for web..

job done!

does that sound right with you folk?
Click to expand...

Well it works but the addition of the resolution is a step that is not required (72ppi or 1000ppi it's still an 800pixel x ??? image.

Try it. Do the same thing and change the ppi to 300. Now look at the image size..... Exactly the same? :)

the only effect of increasing the resolution is to pack the pixels closer together on an actual printed image (making the print smaller).

At 72ppi the 800 pixel image will print out at over 11" on the longest edge although quality will be poor. Change the res to 300 and the image will print at 2.6667 on the longest edge.

With an 800ppi image I'd be able to print a reasonable 6x4 at around 133ppi hence the reason my images are generally displayed as 600ppi on the longest edge.
 
No bother :) I like to promote the correct use of resolution, print size and pixels.

Understanding this really has been a big help.
 
That FastStone seems pretty cool, think i have solved my thickoness of not being able to resize a image properly.............:D Thanks to the one who posted it :thumbs:

Tony
 
There's many converters. I pretty much only use lightroom and batch convert to a specific size.
 
If you have CS2, CS3 or Elements 5+ then you could use the Script Writer scripts (see my sig). They will shrink and border images to whatever size you like, sharpen, convert to B&W, add graphics, add text, add EXIF data and the batch processor that will be released in the new version in the next few days will convert to bmp, png, jpeg, gif etc shrinking the file size to whatever limit you set. Also all the setup is now using graphical editors rather than text files!
 
I think we are talking about two different things with the DPI/PPI. Of course th eimage is the same size but the file size should be less with a lower res - right?

In which case it makes no sense to have a 300ppi image thats only going to be used on a web page.

If I'm wrong about that then I stand corrected. If it doesn't make a difference why even have an option to reduce DPI/PPI in the program?

**********

OK scrub that. You're right - it makes no difference to the file size. Even so I am presuming there must be a reason why an image is set to 72PPI for web use. Is it to do with the way a screen renders the image and there must be some kind of processing going on to show a 300PPI image at 72PPI
 
AndyB said:
I think we are talking about two different things with the DPI/PPI. Of course th eimage is the same size but the file size should be less with a lower res - right?

In which case it makes no sense to have a 300ppi image thats only going to be used on a web page.

If I'm wrong about that then I stand corrected. If it doesn't make a difference why even have an option to reduce DPI/PPI in the program?

**********

OK scrub that. You're right - it makes no difference to the file size. Even so I am presuming there must be a reason why an image is set to 72PPI for web use. Is it to do with the way a screen renders the image and there must be some kind of processing going on to show a 300PPI image at 72PPI
Click to expand...

When you set the size of an image in pixels the ppi value has no relevance. I use this equation which allows three uses. Lets take an 800 x 600 pixel image and we will change the ppi value from 300 to 72 to see what changes.

Ps = Print Size
Px = Pixels
R = Resolution (ppi)

Ps = Px/R

OK You have your 800x600 image at 72ppi. You know the number of Px and you know the R so what you can do is find out the Ps

800/72 = 11.11"
600/72 - 8.33"

Quite a big print but printing at 72ppi will mean a low quality print.

Now the same image at 300ppi

800/300 = 2.667"
600/300 = 2"

This will give an excellent quality 2.67" x 2" print.

Notice what I'm saying here.....

ppi ONLY AFFECTS THE FINAL PRINT SIZE NOTHING ELSE

What affects image size and quality is the number of pixels in your image and the amount of compression you set when saving it as a jpg a lossy format).

Most people use the term dpi but in reality mean ppi. Digital Images are made up of PIXELS. When you print an image what you do is set the size of the pixels to the print - 72ppi the pixels are much larger than 300ppi so the 300ppi image will produce a much finer quality print.

DPI is actually generally used as a PRINTING (Output) resolution. Take my Epson R2400 for example. It has a top resolution of 5760 x 1440.

So I can print my 300ppi images at 5760 x 1440dpi

Do you see the difference?

I think the effective resolution of printers is actually lower than the manufacturer claims but you get the idea.

If you resize in Photoshop, the key drives for changig (or not) image size is the resample image box. If it is checked, any changes you make to the image size will affect the actual image size. Resamping up or down as the case may be,

If Resample is not ticked, any changes to resolution, or size only affect each other - Up the Print Size you will lower the ppi and up the ppi and you will lower the Ps (and vice versa)

You cannot change the real image size which is always measured in pixels.

Hope that helps.

Regards
Jim
 
AndyB said:
Even so I am presuming there must be a reason why an image is set to 72PPI for web use.
Click to expand...

The image size in pixels makes no difference - it does not need to be set to 72ppi for web use.

ppi ONLY affect Print size ;)

What is important is the image size in pixels.

The reason that is important has a lot to do with the standard monitor resolutions. A few years ago when people used a res of 800x600 image sizes on the web were much smaller so that people didn't need to scroll around looking at images. Displayed on a monitor, an image displayed at 100% is mapped 1:1 (pixel; for pixel)

Nowadays the minimum res seems to be 1024 x 768 so an 800x600 pixel image should fit well on that screen. The ppi value has no meaning at this time.

I prefer to keem my web images around 600ppi on the longest edge as people do print my 800pixel imagesat 6x4 size and get pretty decent quality - this has cost me at one event in particular and I won't make that mistake again.

Hopefully you now see why resolution means nowt tioll you actually come to output your image to the printer.

Regards
Jim
 
AndyB said:
Am I not right in thinking you can use the crop tool to resize and alter the DPI at the same time?
Click to expand...

This is what I do.

If I'm printing small images I usually leave the ppi value blank and print at the image default res for the size of image I have.

If I have a 3000 x 2000 pixel image and I want a 10x8 print (I'd need to crop slightly) but I would be able to use the crop tool at 10x8 (empte resolution) and be able to print at the following

R = Px/Ps

3000/10 = 300ppi
2000/8 = 250ppi

So I would print the image at 250ppi. Perfect resolution for a 10x8 print.

:)
Cheers
Jim
 
I'm also using CS3 and can follow the method recommended but it's laborious to open, resize, sharpen and save each image. I'm looking for a solution to batch process images as I often want to resize lots of images to 1024 x 768 and I want to preserve quality.

My workflow currently is to view my fullsize shots in Adobe Bridge in Review Mode, applying labels to the ones I want to process. My question is: once I have my selected group of photos labelled in Adobe Bridge, what's the easiest way to resize the lot of them into another directory (preserving the original full size files)?
 
Roger Ramjet said:
I'm also using CS3 and can follow the method recommended but it's laborious to open, resize, sharpen and save each image. I'm looking for a solution to batch process images as I often want to resize lots of images to 1024 x 768 and I want to preserve quality.

My workflow currently is to view my fullsize shots in Adobe Bridge in Review Mode, applying labels to the ones I want to process. My question is: once I have my selected group of photos labelled in Adobe Bridge, what's the easiest way to resize the lot of them into another directory (preserving the original full size files)?
Click to expand...

Have you not seen Script Writer ??

It can do everything you say and a great deal more. Version 2.11 is out shortly which takes the batch processor even further. It costs £10 and 20% goes to Talk Photography :)

See my sig......
 
cowasaki said:
Have you not seen Script Writer ??

It can do everything you say and a great deal more. Version 2.11 is out shortly which takes the batch processor even further. It costs £10 and 20% goes to Talk Photography :)

See my sig......
Click to expand...

I hadn't seen it but I have now. No offence but it looks a bit complicated and inaccessible to a beginner. What I'm really looking for is something which can give me a menu option when I right-click my selected files in Adobe Bridge and resize all the pics into a new folder.

Mind you, I suppose the complexity of a script is only the initial setting up of it so I should really give it a try.
 
Roger Ramjet said:
I hadn't seen it but I have now. No offence but it looks a bit complicated and inaccessible to a beginner. What I'm really looking for is something which can give me a menu option when I right-click my selected files in Adobe Bridge and resize all the pics into a new folder.

Mind you, I suppose the complexity of a script is only the initial setting up of it so I should really give it a try.
Click to expand...

It has an installer so you don't have to worry about that.

Basically you run photoshop as normal then goto scripts and browse to the installer which you select.

Then you restart photoshop and all the scripts are installed. You then run "EDITOR - USER DATA" to set your details up which again is automatic.

Then you can just use each script but to edit them you click on EDITOR - EBS SCRIPT and change the values in the boxes! so change 800 horizontal to 1024 etc. Then click save and give it a name. Once you are happy with that script you can call it at any time by clicking on that name from the menu!

If you then want to batch process it you simply click BATCH and select YOUR script, the directory containing your pictures and then the new directory. It will then go ahead and complete all the changes.

The new version which will be out in a few days processes an entire tree of folders rather than just one!

Basically it is scripting without the scripts - You never have to look at any programming !! I have done all that for you :)
 
OK so there is an advantage to reducing PPI to 72 for web use because someone stealing the image to print is going to get a pretty cruddy result. If the web page has an image at 300PPI then the stolen image will produce a better result.

Thanks for the clarification.
 
Thanks for the explanation, I'm trying it now. Some initial thoughts:

When batch processing the EBS resize 800 only script can the file browser windows not remember the last used setting? My photos are buried in lots of sub folders on my E: and browsing to them each time is tiresome. Ideally the source file folder dialog would open to the last used folder as default and the output file folder would use the input folder as a default so you could just click into a subfolder as desired.

Biggest problem for me right now is the quality of the resized pics. They are horrendously over compressed and blocky. File sizes are 10 - 20kb only. Really unuseable. I looked using the EBS editor but I can't find a quality setting in the resize 800 only script. Any ideas?
 
have a look at image resizer free tool by microsoft - just right click on a image pick the size job done or right click on a folder and it resizes all the images in the folder and its free
 
Thanks Dogfish but I already have and use the Windows image resizer, but find it degrades the JPG quality. I'm looking for a solution which will preserve quality and be quick and easy to use.
 
I've been playing around with the automate > batch feature of photoshop and if you simply record an action to resize your pics you can run an automated resize on any number of photos. The quality of the resized pics is great compared to the other methods. :thumbs:
 
Roger Ramjet said:
I'm also using CS3 and can follow the method recommended but it's laborious to open, resize, sharpen and save each image. I'm looking for a solution to batch process images as I often want to resize lots of images to 1024 x 768 and I want to preserve quality.
Click to expand...

Very simple to do. Use an action. Resize on one image and record your action. Then sun a batch action to the required images.
 
AndyB said:
OK so there is an advantage to reducing PPI to 72 for web use because someone stealing the image to print is going to get a pretty cruddy result. If the web page has an image at 300PPI then the stolen image will produce a better result.

Thanks for the clarification.
Click to expand...

THERE IS NO ADVANTAGE.

When you set the image size in pixels, that is an absolute size. Print size of that image is dependant on how the image is set up fr printing.

If I copy your 600x400 image off the web at 72ppi I can change it to 300ppi myself without changing the size of the image (it will remain a 600x400 pixel image).

ppi can also be called PPPI - PIXELS PER PRINTED INCH

PPI HAS NO EFFECT ON WEB IMAGES

Save two files both 800 x 600 pixels in size. Save one at 72ppi and the other at 300ppi (or more if you like)

Save them at the same quality.... What image is bigger?

I'm sure you can work this out and let us know.....
 
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