Loss of quality after resizing - DPChallenge Forums

Nikon AF-S NIKKOR 24-70mm f/2.8G ED

12/14/2007 10:50:20 AM · #1

Before resizing the picture quality is excellent zoomed or unzoomed. After I resize my photo per DPC spec's the quality of the picture decreases, i.e. jagged edges primarily especially noticable when zoomed. I have tried three resizing utilities with the same results. What could cause this or am I doing something wrong?

Here are the before and after specifications.

BEFORE
width 2635 pixels
height 1754 pixels

AFTER
width 640
height 426

What am I missing?

Thanks for your help.

Message edited by author 2007-12-14 11:07:24.

Dirt_Diver

Nikon D3s

12/14/2007 11:20:37 AM · #2

Nothing, that's what happens. To make it somewhat better when you resize make sure the DPI is 300

bassbone

Nikon Z8

Nikon NIKKOR Z 24-120 f/4 S

12/14/2007 11:22:41 AM · #3

This is a repeat of another thread...

HERE

Nikon AF Nikkor 50mm f/1.4D

12/14/2007 11:35:22 AM · #4

Originally posted by bassbone:

This is a repeat of another thread...

HERE

Hi bassbone,

I placeed my question in two subforums for maximum exposure. Whereas...

....when a topic is placed in the Members Discussion subforum the post is limited to input from members only.

....when posted in Photography Discussion subforum the post has the potential to input from members AND nonmembers.

lp

Prof_Fate

12/14/2007 11:46:27 AM · #5

DPI doesn't matter - it's only for printing - dots per inch - and we're talking screen res here.

What software are you using?

In PS you go to Image-Resize and type in the 640 for the longest and go. There are some settings - resample (yes) and various versions of that (bicubic smoother etc). Default should work.

Now when it's resized remember it's MUCH smaller than your screen, so don't view it at anything larger than 100% or it will look as you're describing it - poor quality and jaggy, etc.

When you save it try to keep the quality at 70-80%. Most folks save with "Save for Web" (and devices in CS3) and there you can choose the file size (147k) and let it do it's thing.

rossbilly

Nikon D200

12/14/2007 12:21:55 PM · #6

How about posting an example, and then describing the exact steps taken to resize? That way, we can see where the issue is occurring, rather than letting us imagine what the problem might be...

Not trying to be a smart ass, just pointing out that there MIGHT be something you don't notice, but someone here could easily recognize the problem. The devil's in the details! ;)

Billy

Olympus OM-D E-M5 Mark III

12/14/2007 12:40:39 PM · #7

If the software you're using is causing jagged edges etc. when you resize (and if you don't have Photoshop), then FastStone offers a good alternative.

Using FastStone I thought the 'Bell' and 'Mitchell' algorithms gave the best quality for upsizing, and 'Lanczos3' the best for downsizing. FastStone is freeware for non-commercial use from here

To be honest, I think it's more likely the case that you're zooming in to a 640px image and seeing the blown up pixels.

Yo_Spiff

Olympus 12-100mm f/4.0 M.Zuiko ED IS PRO

12/14/2007 02:13:42 PM · #8

As JHonan said,the resampling algorithm used by your software to downsize it has a huge effect on it. Here is a folder with some examples, showing the different methods of resizing that I can do in PaintShop Pro, and the results:
//www.dpchallenge.com/portfolio_mgr.php?collection_id=25726

"pixel resize" looked pretty nasty. I find I usually get the best results from "bilinear".

Resizing also tends to blur the image. A touch of sharpening after the resize will help there.

Message edited by author 2007-12-14 14:14:39.

12/14/2007 04:11:03 PM · #9

Originally posted by Venom:

--------------------------------------------------------------------------------
The reason the original is clear is because it's size is probably a greater resolution than your monitor settings. Therefore when you zoom in on the original you are still viewing it at less than <-100%. Once you've resized the image your monitor can now handle the whole image at full resolution. Now when you try to enlarge your smaller (640) image you are actually viewing it anywhere from 110% - 150% depending upon the amount of zoom you apply. Does this make sense?

Venom's explanation is the exact reason.

Given:
A. My Samsung Syncmaster 206BW (20") Digital Monitor is 1680x1050 pixels

B. The original photo is 3008x2000 pixels.

C. The resized photo is 640x426 pixels.

Therefore:
The original photo's 3008x2000 resolution is greater than that of the 1680x1050 monitor but when the 3008x2000 photo is resized to 640x426 the 1680x1050 resolution of the monitor is obivously far greater therefore the 640x426 image appears inferior when zoomed or magnified.

There was much good information provided regarding resizing. You all have help me and other better understand the process.

Lp

12/14/2007 06:07:43 PM · #10

RE:
"The original photo's 3008x2000 resolution is greater than that of the 1680x1050 monitor but when the 3008x2000 photo is resized to 640x426 the 1680x1050 resolution of the monitor is obivously far greater therefore the 640x426 image appears inferior when zoomed or magnified."

Here are links to two samples. The first sample shows the clean 3008x2000 while the second shows the jagged 640x426. When you zoom or magnify the images you should be able to see the difference. Unless the resolution of your monitor effects the images.............

(my apologies for using links vs. actual pictures, the insert image and insert thumbnail link buttons do not function with my new Vista based system.)

SMOOTH
//images.dpchallenge.com/images_portfolio/70594/thumb/622373.jpg?0

JAGGED
//images.dpchallenge.com/images_portfolio/70594/thumb/622374.jpg

Message edited by author 2007-12-14 18:09:31.

Canon EF 70-200mm f/2.8L IS USM

12/14/2007 06:09:44 PM · #11

Originally posted by louisp:

(my apologies for using links vs. actual pictures, the insert image and insert thumbnail link buttons do not function with my new Vista based system.)

Just type [thumb] and then the number 622373 and then [/thumb], without spaces.

Photologist

Apple iPhone 16 Pro Max

12/14/2007 06:18:38 PM · #12

I know when using Photoshop, resampling the image is recommended when reducing its size. The recommendation is to sharpen a bit. In PS, that would be "bicubic sharpening" . . .

12/14/2007 06:19:21 PM · #13

[thumb]622374[/thumb]

That's not 640x426. What method did you use to resize it? btw - When resizing for the web IGNORE the dpi settings.

12/14/2007 06:21:14 PM · #14

Originally posted by jhonan:

[thumb]622374[/thumb]

That's not 640x426. What method did you use to resize it? btw - When resizing for the web IGNORE the dpi settings.

The image shown is a cropped section from the 640x426 image.