# Resize without losing  quality



## Rick58 (Oct 1, 2012)

Is there a quick and dirty procedure for reducing the size of an image without losing quality.

I resize by entering to new max pixels then attempt to re-sharpen the photo, but the images always lose a lot of detail.
Maybe I'm asking too much by attempting to resize too drastically. How much can you reduce without seeing a major loss of detail? 
I realize there are many variables that will influence that answer, but for just conversation are we talking quarter, half, more, less the original size?


----------



## 480sparky (Oct 1, 2012)

Are you trying to make the image larger, or smaller?

If you're going big, you can't create data that isn't there.  So the software fudges the process and 'makes it up'.

If you're making 'em smaller, you're giving the go-ahead to throw data away.


----------



## Rick58 (Oct 1, 2012)

Smaller. The Red Barn photo I just posted is a perfect example along with the Bernhart Dam. I don't recall the spec's of the Dam photo, but the Barn original was a tad over 10 megs and TPF wouldn't accept it, so I had to reduce. Both a far inferior to the original.


----------



## Big Mike (Oct 1, 2012)

There are two main ways we reduce the size of a file.  The first one is resizing it...reducing the number of pixels.  This is usually great for uploading to the web because the files from our cameras are several thousand pixels by several thousand pixels....but for displaying on a monitor, you only need about 800-1000 pixels wide.  If you upload a 'full size' image, the software may resize it again, which may be the point at which the quality is affected.

The second way we reduce the file size, is to compress the image/data.  When you save as a JPEG, you have the option to adjust the quality/compression.  With a good photo, you could probably dial it down to less than 50% quality (high compression) and nobody would even notice.  

So what I usually recommend, is that people resize and compress their photos themselves, so that they have a good looking image with a small file size (and small pixel size).  That way it should display in the forum without any interference from the browser/viewer software.  
I'm not really sure how the current software works, or what it's limits are...but the usual culprit is people trying to upload images that are too large, with big file sizes.


----------



## Judobreaker (Oct 1, 2012)

How much are you resizing?
You definitely 'lose' data when resizing because you simply can't put all the data of a large original in a smaller file.
If you're resizing little bits there's nothing to worry about.
If you're resizing a lot there are a few situations in which you need to careful.

There are cases with which resizing can cause weird things to happen.
I'm talking about the moiré effect.
Here's a nice article explaining what it is and how you can avoid it. It's a simple trick but it works wonders.

Photoshop tips &#8211; avoiding moiré when resizing « Neil vN &#8211; tangents


Besides that: There's nothing more to it than just resizing and sharpening. ^^


----------



## Big Mike (Oct 1, 2012)

Also, make sure that your photo is in the sRGB color space.  If you have it in AdobeRGB or something else, it won't be read correctly by web browsers, and thus, it won't look how it should.


----------



## KmH (Oct 1, 2012)

Are you selecting *Resample* in the resize dialog? And if so, what sampleing algorithm are you selecting?

What *Quality* setting are you using when you *Save* the image?


----------



## The_Traveler (Oct 1, 2012)

My guess would be this:

In your original image, either non compressed jpeg or a converted PSD, you were able to see many details including fine grain and tone changes in the wood - even if the adjacent tones were very very close in hue and saturation because each pixel in the original image was kept and represented on the screen.

In the smaller image, this 'detail' went away.

This is because, when making an image smaller and compressing it somewhat to get into the size requirements for the web, the software is looking at adjacent pixels and, if they are relatively close in tone, the software will just average the value and remove the difference. What was a visible difference before will be erased in favor of a smaller file.

The size of 'closeness' threshold is determined by two things: how much you are reducing the image and the desired quality of the resulting image. [Higher quality = less compression and a higher threshold for any averaging]

Thus the more you decrease the dimension and the lower the quality required (the higher the compression) the more that that adjacent pixels of differing tones will be averaged into one shade.


----------



## Rick58 (Oct 1, 2012)

Thanks guys, there's a lot here for me to sift through and I won't know many of the answers until I get home in front of my PC. I now need to do some homework  and experimenting. Thanks for the help and advice. This has been bugging me for awhile and I never took time to look for answers. Thanks


----------



## MLeeK (Oct 1, 2012)

I've found that if I sharpen to SHARP before resizing it's usually super sharp when sized down.
What are the pixel dimensions you are using? And then how large are you viewing it?


----------



## Tee (Oct 1, 2012)

My quick and dirty in CS5: click 'image' then on 'resize'.  For web use I resize to 800 on the long side so which ever has the highest pixel count gets resized to 800. In the same box, click on the drop down box and select 'bicubic sharpener' then click ok and that'll resize the image.  Once that's done, hit magnifying tool and then 'actual image size' and you'll see what it'll look like.  From there I use the 'save for the web' option and continue on. If you use the save for web option make sure you do not select bicubic sharpener again as it will over sharpen.


----------



## Rick58 (Oct 1, 2012)

I *THINK* I found my problem. I'm using Photo Pro 3 and there is an advance save option screen. My problem was with the compression setting. I added a photo to the Red Barn thread using the new settings. Much better IMO


----------

