photoshop resizing problem

ajmall · Nov 29, 2004

i've noticed recently that when i reduce the size of my photos (usually by a significant amount around 50%) they actually lose quality and become grainy.

i use the "image size" tool and have altered both pixels and dimensions yet it makes no difference. how can i stop this from happening? or, how can i reduce image file size with only reducing the image size by 20% and without losing quality?

thanks

Mo · Nov 29, 2004

Only change one value and check the "Constrain Proportions" box. Mine never lose quaility.

The "Constrain Proportions" box is at the bottom of the resize window, if you don' already know.

ajmall · Nov 29, 2004

i did that but i still didn't get the desired effect. i need the file size to be small without losing quality

Mo · Nov 29, 2004

I see. I have also experienced something similar: my Coppermine photo gallery creates a 400 pixel, 22Kb intermediate image, while in Photoshop it was 88Kb at JPG 7. Alything below that looked worse than the 22Kb image. I don't fully understand this, either.

How big (in pixels) are your images and what size do you want to resize them to?

ajmall · Nov 29, 2004

well i'm working in cm as the numbers are smaller and easier. the pixel size varies but the most recent i tried was about 1500 by 1900. i reduced the image size and it went really grainy. strange thing is you only expect that when u make an image bigger!

Mo · Nov 29, 2004

Strange.. :?

MarylandMatt · Nov 30, 2004

Are you zooming in at all? Or viewing the image at 100% I know that sometimes on PS7 when I zoom in, it will get pixelated of course. Even at 110% it will look fuzzy.

ferny · Nov 30, 2004

Does it look grainy or are you really seeing jagged lines?
Think about this, get a piece of cloth 6"x6" and lay it flat on a surface. Now push the sides in until it is 3"x3". Not flat is it?
A similar thing happens when you make an image smaller. Except because it's 2d and not 3d the bits of cloth poking up in the air get thrown away. As a result, perfect circles and straight angled lines became jagged. Straight horizontal and vertical lines are fine. So the loss in quality of certain images doesn't always notice. At other times, it can ruin the entire photo.
The more you resize the image, the more that gets thrown away the worse it looks. Photoshop is very good at resizing images.

Nytmair · Nov 30, 2004

also, if you are saving the image for web (i.e. as a jpeg or gif) you are able to change the quality at which you save the photo... i usually do 80% (high quality) but you can go higher or lower.... obviously the highter quality, the higher the filesize as well.

Just another thing to check

BernieSC · Nov 30, 2004

When I resize a photo I always use the smart blur or blur the photo slightly that cleans up pixelation when you reduce the size and if it looks a little blurry after resizing i use the sharpen edges filter.

If you haven't tried the smart blur filter try it. I love that filter it really makes smoothing and adding a great look to the photo really easy.

ajmall · Nov 30, 2004

no im not zoomed in past 100%

thanks for the tips. i'll give blurring a go.

jadin · Nov 30, 2004

Are you using bicubic resizing? If so that's your problem. It might work for upscaling but downscaling makes it look horrid. Try the other options until you find which one looks best.

I'd just tell you which it is, but I use paint shop pro which has a "smart size" and works insanely better than any of the other options.

Digital Matt · Nov 30, 2004

Bicubic resampling does not make a photo look horrid when resizing it smaller. Do any of my pictures look horrid? They are all bicubically resmapled from 3072x2052, to 650x434, and they look fine. Second of all, you definetly don't want to blur an image that you have scaled down. Pictures that are made smaller lose detail and sharpness. They need to be sharpened, not blurred. The fact of it is that photoshop decides what pixels it can do without, and throws some away, hence lost detail.

As for your pictures becoming grainy, I can't say. Does the photo immediatly look bad after resizing, while still in PS, or is it after you've saved it and view it in another program? Can you post an example? It's most likely something you are doing, because I have never heard of photoshop doing this, but it might be a program error as well. I'd love to see an example. If you could upload an uncompressed jpg, quality 12, and just link to it so it doesn't kill us all here, that would be helpful

jadin · Dec 1, 2004

Digital Matt said:
Bicubic resampling does not make a photo look horrid when resizing it smaller. Do any of my pictures look horrid? They are all bicubically resmapled from 3072x2052, to 650x434, and they look fine.

Actually it does. 3000 to 640 is quite simply not a big enough jump in sizes to see it happen. I tried it on one of my photos from 3000x2000 to 640 and it looked fine. I resized from 4000 to 640 and it instantly when to crud. (only command done on these was resize)

Resized using bicubic:

Resized using blinear:

Resized using pixel resize:

Resized using weighted average:

Resized using smart size:

You tell me which ones look good.

ferny · Dec 1, 2004

jadin said:
I'd just tell you which it is, but I use paint shop pro which has a "smart size" and works insanely better than any of the other options.

I use PSP as my main editor to. But I've always found it to be horrible at resizing images. I use Photoshop for that sort of thing instead. Maybe I've missed a button in PSP. :?