Adobe Photoshop

**joyforlife36** · 12-31-2005, 03:58 PM

Hi, I have been designing web sites and working with Photoshop for 4-5 years and am pretty good at it, but with no formal training in graphic design, I am still weak in some areas. I still do not have a full understanding of the whole "resolution vs size" thing with photos and graphics.

Right now I have a jpg photo sent by my client that is about 120x220. Resolution is 300. What I need it to be is about 240x440 with a resolution of 72.

Is this possible? If so, HOW? Thanks in advance!

**0beron** · 12-31-2005, 09:43 PM

Size is how many pixels there are, resolution is how far apart they are. Just resize the image to 240*440 pixels, then if you want a resolution of 72 dots per inch, print it out so that it is 3.3 * 6.1 inches.

The two are often confused since we refer to pixels on screen as 'screen-resolution'. In the days of CRTs this was true as changing resolution actually put more dots in the same space - with an LCD panel there are fixed pixels.

**joyforlife36** · 01-01-2006, 09:54 AM

Thanks for the reply. I did try to resize it as you said, but it comes out blurry and grainy. I am hoping to keep it crisp. Is there some trick to maintaining the quality?

I use Photoshop 6. I tried several different ways. I went into Image>Image Size and then fooled around in there with different settings. Nothing worked. Then I tried the Help>Resize Image to no avail.

So, sorry to say, I need you to talk to me like I'm an idiot. :-)

**Miki** · 01-01-2006, 04:14 PM

You could always use Photoshop CS2's Smart Object feature.

If you dont have CS2, feel free to PM me and I will happyly resize the image for you (for free of course).

I think you can use jpg's as smart objects to resize without it getting to blurry or grainy, not 100% sure though.

**vangogh** · 01-01-2006, 05:28 PM

I'm not a Photoshop expert, but I think you're going to have some blurriness and graininess to your new image the way you want to resize it. No matter what you do you only have so many pixels in the orignal image and your resize needs more pixels to display crisply with your new image size and resolution. If it doesn't have those pixels Photoshop has to guess at what color each should be and while it does a good job there's no way for it to be perfect.

Unfortunately the only way to get those pixels is to get a better original image.

I hope I'm wrong, but I don't think I am. Someone with more Photoshop knowledge can probably give you some techniques to help, but I'm pretty sure your resized image is going to have a hard time looking as crisp as the original.

**joyforlife36** · 01-01-2006, 10:48 PM

Thanks for your offer, Miki. I may take you up on it since I do not have CS2 yet. Unfortunately the forums will not allow me to PM you right now since I have not made 5 posts yet !

vangogh - I knew it was hard to upsize an image and maintain quality, but I was hoping since I only needed 72 dpi and this was 300 dpi, somehow that would make the difference.

but, thanks for all your help.

**vangogh** · 01-02-2006, 01:42 AM

Liz, I may be wrong. I have some skill in Photoshop, but I'm far from an expert and there's much I need to learn with the program. That's just been my experience. I can never remember all that pixel and resolution stuff and the specific math in the resizing.

So I tried a small experiment before posting earlier. I took a 120x220 image (just a white background i created new) and changed the resolution from 300 to 72. The image droped in size to something like 37x67 (I don't remember the exact numbers) That's the equivalent size image to Photoshop after the resolution change so it's hard for me to see it being crisp when taken back up to 240x440.

I do hope I'm wrong and if anyone knows a way to get this to work please post how. I've had the same issue before when clients didn't have original images for me and all I had to work with was a smaller image than I wanted.

**jackski** · 01-02-2006, 04:39 AM

Please follow this link to another forum where they are talking about this subject. sometimes resizing and changing resolution are spoken of as the same thing. Many questions will be answered from the link below
http://forums.dpreview.com/forums/re...hread=13405719

**jackski** · 01-02-2006, 04:46 AM

This is another interesting link about DPI and it's effects on images.

http://forums.dpreview.com/forums/re...5&changemode=1

**0beron** · 01-02-2006, 04:57 PM

Here's how I see it: Resolution and size are independent of one another - you can change either one without affecting the other. Attached is a picture to try and show this - On the left is an original image. Making the size bigger means there are more pixels to fill than you had originally, so you have to interpolate. I show one with no interpolation (nearest neighbour) in which each pixel in the original becomes 4 in the new one. The other one is the same size in pixels, but with the pixels interpolated to smooth out the square edges on the blocks of four pixels - this causes the blurring.

Below this I show a resolution decrease (i can only show a x2 decrease since anything in between wouldn't match up with the pixels on the screen. Printers can print at a variety of dpi settings so they can produce some or all of the intermediate values).

The size in pixels is the same as the original, they are just further apart. (Yes I know it looks twice as big, but I had to do something to show the increase).

Decreasing the resolution and keeping the size in pixels fixed, means the size in inches when you print it will be larger.

For your image, just resize with whatever interpolation setting you want to avoid blurring. The resolution can be controlled later when it needs to be printed.

**joyforlife36** · 01-02-2006, 10:16 PM

Thanks very much for your reply. I do not want to print this photo, however, it is for web design, hence my desire for 72dpi. What I am realizing is that I cannot do what I really want to do.

I appreciate all the help that was given.

**jackski** · 01-02-2006, 10:28 PM

Quote:

Originally Posted by joyforlife36

Thanks very much for your reply. I do not want to print this photo, however, it is for web design, hence my desire for 72dpi. What I am realizing is that I cannot do what I really want to do.

I appreciate all the help that was given.

Yes you can, all you do is resize to 240x440 and then change to 72dpi without altering the size. as a matter of fact you can do it easier in a free program called IRFANVIEW.

**joyforlife36** · 01-02-2006, 10:58 PM

Jackski - How do I "resize" without "changing the size"? I'm sorry I am not getting this. I guess I need someone to just walk me through it step by step.
I have tried a lot of things that people have suggested, but it always looks blurry. And I have no idea what interpolation is or how to control it.

**jackski** · 02:56 AM

Hi, This is a copy from one of the links I sent you. I believe it explains the procedure that will give you the result you are looking for.

The first thing you will see is there is three section.

The Top section is the file size lets you see how many pixels you have. The number of pixels determine the file size.
The middle section is the Document Print size. More on this later.

The bottom section is the control section. This is where you control how the image is resized. The first thing you want to do here is to un-check resample. Resample is the main control. When this is un-checked the file size will not change. This means that photoshop will not get rid of any pixels or add any interpolated pixels. With resample un-checked the top part will be grayed out un changeable.

Return now to the middle part the Document Print size. If in the bottom section Constrain is checked all you need do is change one value in the document print size and photoshop will change the other two. Lets say you want to print an 8x10. Change the longest side height or width to 10 Photoshop will change the other side to the size it should be to keep the same proportions. It will also show you what dpi the image will print at. If the dpi is low below 200 it time to use resample. Now check resample and change the dpi(resolution) to 300 the width and height will stay the same but Photoshop will add pixels to increase the dpi to 300. The top section will show the new file size the number of pixels will change.

The other time you want to change the file size is when you want to make the file size smaller so it will load faster in a web page or you want to create wallpaper for you display. I normally use the top part of the Image size to reduce the file size. I open the Image size dialog check constrain and resample and change the top section like width to 1600 to resize the image for my 1600x1200 display.

**0beron** · 01-03-2006, 07:46 PM

If it's for web design or viewing on-screen then resolution in dots per inch is irrelevant. People who view your website are looking at an array of pixels in fixed positions - you control the colour of some of those pixels with your image. If you want to cover a bigger area you have to inflate the image with some possible distortion or blurring, or get a bigger original. If people view your image an a CRT monitor and then change their screen resolution, your image will appear larger or smaller on screen.

I'm confused about what exactly happens when you change the 'resolution' of an image in a graphics app such as photoshop. Say your image is 50 dpi, and you increase to 100 dpi - does this add pixels to the image so that when printed at the same physical size in inches, the image is at 100 dpi, ie four times as many pixels? This is just another way to increase the size if that is the case...?

**jackski** · 01-03-2006, 09:59 PM

Quote:

Originally Posted by joyforlife36

Jackski - How do I "resize" without "changing the size"? I'm sorry I am not getting this. I guess I need someone to just walk me through it step by step.
I have tried a lot of things that people have suggested, but it always looks blurry. And I have no idea what interpolation is or how to control it.

Hi, first of all you need to do this...The first thing you want to do here is to un-check resample. Resample is the main control. When this is un-checked the file size will not change. This means that photoshop will not get rid of any pixels or add any interpolated pixels. With resample un-checked the top part will be grayed out un changeable. You then size your image.I have done this many times and have never got blurry images. In your case you may need to crop first to get the format correct, as your photo is not standard ie 8x10, 7x5.
Then you check resample and change the dpi to 72, the size will not change.

**vangogh** · 10:49 PM

Thanks jackski, I realize the original question wasn't mine, but I've been learning a lot here about better ways to resize the images I work with. I'm far from a Photoshop expert, but I can certainly get around well enough in the program to handle the work I have to do with the program.

Starting tomorrow though I'll be a little better. I always wondered what resample did and now I know.

Oberon, if I'm not mistaken when you increase the resolution in Photoshop from say 72ppi to 300ppi Photoshop adds in the extra pixels you need and uses interpolation to decide what color the new pixels should be. It does a very good job, but obviously can't be perfect which is why adding those pixels tends to make things a little blurrier or fuzzier.

**0beron** · 01-04-2006, 02:49 PM

I thought so. Thanks for clarifying. As long as the image is on your screen or in memory, it has no 'resolution' at all - its just a pixel array. When you print it, that is when resolution is important.

**westykid** · 01-17-2006, 08:34 PM

Blimey - some confusion over this one:

Image size is inversely proportional to image resolution - that is for an image with the same number of actual pixels - if you double the resolution, the image will be half the size (a quarter of the area) at the new resolution and vice-versa.

Your original image is 120x220 pixels - that's the file size - the resolution is irrelevant - You want an image 240x440 pixels - that is exactly double the width and double the height. This means Photoshop must interpolate (guess) how to make 4 pixels from every 1 you have in your image - a tall order. - In the image resize dialogue set the resolution to 72dpi. Then put the width and height values in the PIXEL DIMENSIONS fields and make sure 'Resample Image' is set to 'Bicubic Sharper' or 'Bicubic Smoother' depending on whether your image has hard lines (like a graphic) or smooth tones (like a photo of a face) in it. Just try it out and see which works best - The resampling will make the image blurry - you can correct this to some affect by using filter->sharpen->unsharp mask. I suggest a setting of around radius=1.0, threshold=0, and amount between 110 and 130%. Just have a play and see what is acceptable - This can be a great quick fix for a blurry image but if it is too harsh will introduce artifacts and hard edges.

PS. If you've got text in the original - it's going to look crap anyway - see if you can isolate it and then redo it in the larger image.

**westykid** · 01-17-2006, 08:36 PM

Just had a thought - since your desired image size (in pixels) is exactly double the original's - you should try using 'nearest neighbour' as the resampling method instead of bicubic - it might give a better result.