# Confused about photo editing



## dalemcginnis (Sep 17, 2007)

Trying to understand how my photo editing software (Corel Photo House) sizes pictures and determines file size and am totally lost.

Took three pictures of the same pen with the same camera settings, only difference is distance between camera and pen. After croping the picture I came up with the following sizes:
408 x 877 361Kb
450 x 951 251Kb
394 x 951 434Kb
All too big to upload.  After playing around with the image properties I finally got the follwing results:
418 x 882 1107.8Kb(corel) 183Kb(windows)
340 x 680 693.6Kb (corel) 236Kb(windows)
388 x 834 970.8Kb (corel) 234Kb (windows)
I can't see any correlation between the frame size of the picture and the file size.  Also why does corel have a file size so different from what windows says the saved file is?
For reference here are the three photos:


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## Dario (Sep 17, 2007)

Dale,

First I am also lost but the way I understood it is there are 2 factors to consider.  One is the picture size and the other is the resolution (pixel/inch).

Resolution is like density and a small picture that is very dense can be bigger filesize wise than a bigger picture of lower resolution.  Certain colors use more space too.

I try to keep my pictures at 72 pixels/inch and 8" x 10"  up to 9" x 12" size.  Different software does their compression differently...some loose a lot during the compression and obliterate the picture.


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## dalemcginnis (Sep 17, 2007)

Dario:
Thanks for the info, but that makes my software even screwier.  All three pictures are at 72 pixels and were the whole time, I never adjusted the pixel size.  I just checked their dimensions and they are:
5.81 x 12.25 inches
4.72 x 9.44 inches
5.39 x 11.5 inches

So according to that, the bigger my picture is the smaller the file size?[?]


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## gerryr (Sep 17, 2007)

Image files sizes are fairly complicated.  For one thing, a confusing background like you're using will make the file larger because the sensor has to record more detail.  A plain background will make the file smaller.  I don't know anything about Corel Picture House, I use Paint Shop Pro Photo X2, but I've also used Gimp and Picasa.  I would recommend you download Picasa from Google, it's free and has a pretty good resizing utility.  Basically what happens when you resize a photo is that the file gets compressed.  The larger the file to begin with and the smaller you need the final result, the more the file gets compressed.  In the compression process, detail is lost.  

If you're running Windows XP, go to the Microsoft website and do a search for XP Powertoys.  You can download the picture resizer for free and it works quite well.


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## Dario (Sep 17, 2007)

Like Gerry, I use Picasa too (and recomend it) but most of the time I use Adobe PhotoShop now.


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## dalemcginnis (Sep 17, 2007)

Thanks, I think you solved my problem. I use Adobe to upload my photos from my camera and also to crop them.   I did not see a resizing tool in it, but the XP Powertool looks like it is exactly what I need. I've downloaded Picasa and will play with it. 
As for my background, until I can get me a light tent setup (a few more weeks) I'm kind of stuck with the tree as its the best place I've found to take pictures of my pens.  Besides, it's real easy to make sure my pen is in focus with that background.[]


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## fstepanski (Sep 17, 2007)

Not an expert however here is what I understand..
Essentially re-iteration of Dario & Gerryrâ€¦
With digital images there are several factors, which equate to file size.  
Number of colors i.e. complicated background = larger file size
Size i.e. dimension 480 pixels by 280 pixels
Resolution 600 dpi image will be larger than a 72 dpi
You can apply several types of compression algorithms to a .jpg image  

I'm not familiar with Corel try a "save as" feature and see if you have an "OPTIONS" button...
Good luck...


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## toolcrazy (Sep 18, 2007)

I recently started using Adobe Photoshop Elements 5.0 and I like it. It handles downloading my photo's from my camera, cropping, resizing and enhancement. Even though I have Photoshop CS, I seem to turn to this one more often anymore. My recent pics that I put up are 600px wide and are less than 100k in size and if you look at them, there is very little loss.


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## gketell (Sep 18, 2007)

there are many things that affect file size.  

First lets talk raw files which is what the camera captures at the sensor.  THAT file is always the same, it is LxWxD: length in pixels, width in pixels, depth (number of colors per pixel).  So if you have a 1024x768 monitor with 8 bits of color (256 colors) you end up with 1024x768x8=6,291,456 bits or 6.2Mb or .78MB big.  A 1024x768x32 bits of color (429 Million colors) = 3.14MB of file size.
A 450x951x32 bits ends up being 1.7MB big.  So if you shoot in "raw" mode this is what you should expect to see saved to your memory stick/hard drive.

The JPEG file type has several different levels of compression and which one you or your software choose directly affects the file size.  One example of compressing is taking 10,000 sequential 1's in your file it can be compressed down to 1 1 and something that says "10,000 of those things" so a pure white or pure black background is more easily compressed down to a smaller size than a "diagonal gradient" where every pixel is different from its neighbor in every direction.  On minimum compression the algorithm would "say" "that is a different color pixel so I will record both" where on maximum compression it would say "that is within 10 or 20 shades of the next so I will merge them as the same".  The more you compress, the more you get "jaggies" from that merging of "similar" pixels.

DPI (dots per inch) really doesn't apply to your monitor screen and only truly applies to printers.  It represents how many dots of ink the printer can put down and/or how many you want it to put down (if that is less than the maximum the printer can do).  If you are printing a small object you need less DPI because the "lines of differentiation" are closer together than when you print a big object.  Imagine, you take your favorite pen picture and make a 3"x5" print of it.  In this situation the edges of the pen are physically only 3/4" apart (nearly life size).  The "lines of differentiation" of color (the grain, the slope of the nib, etc) are very close to each other so a few dots fills that in nicely.  Now take the same photo and blow it up to 3'x5'!  The edges of the pen will be 4" apart (12 x the 3/4" from before) and the "lines of differentiation" will be several inches apart.  If you don't have enough DPI then that will look really carpy so you will want 300dpi or better.  ((inline foot note: the optimum DPI for printing on epson photo printers is 360DPI.))

Your monitor, on the other hand, doesn't care about DPI, it only cares about pixels.  If your camera could take a picture 1024x768x32 and your monitor supported 1024x768x32 that picture would look perfect on that monitor.  If you displayed the picture edge to edge on a bigger monitor, it will look progressively worse as the monitor gets bigger because the monitor has to try to figure out how to "interpolate" what should be between each of the pixels that it actually knows about.  (If you want to see this in real time open you picture in any editor and then zoom to 200% or 300%, etc).

So when saving you picture for the web, how does DPI affect your picture?  It doesn't.  But, your software tries to simplify your life and not get into the DPI vs Pixel/Print vs Display discussion and simplifies it all down.  

So in the terms of what you software will tell you about, to make your picture good for the web you want to "resize" your photo to 800x600x72dpi in RGB mode (the norm) and, if your software has it, "Web ready" which will decrease the bits of color to the minimum to accurately represent your picture.  I use those setting and "jpeg quality 8" which in my software is 1/3 compression and all my photos come out right around 100KB and look great.

If you are using Adobe Photoshop (vs photoshop elements which I don't remember) you resize the file by going to Image:resize.  And when you crop it you can specify a DPI setting.  So, I would do it in this order: Crop it to the size/shape you want (leave DPI alone to keep best quality); resize it to the size you want; "save as..." jpeg, quality 8, progressive.  That will 95% of the time get you to what you need to post here and leave your original picture at full size/color depth so if you want to make the 3'x5' print in the future you still can.


GK


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## leehljp (Sep 18, 2007)

Greg knows his stuff. As others said it is complicated. I have used Photoshop since '92/'93. In trying to simplifying the explanations lets say that In photos - there are two different animals - 1. printed photos and 2. (computer) screen/web photos.

Printed Photos and Screen/Web Photos are almost polar opposites in sizes.

SCREEN/WEB DISPLAY PHOTOS
Screen/web photos derive their color from light and lighted background. This causes the eye to be tricked in what it sees in both color and resolution. Screen photos do not need a whole bunch of dots (either pixels or dots per inch - i.e. DPI) to make it look good on a computer screen, therefore screen and web photos can be very small in kb size and still show good pictures that would otherwise print terrible. Different color lights blend and mix and trick the eye into seeing colors that are not there. This makes it easy to achieve lots of colors that would be ugly if printed. This is why screen photos are smaller in kb size than those used for printing. Also, a good computer can simulate millions of colors with the three basic light colors - RGB - red green blue. As far as photos go - not much needed in kb size to do that.

NOT directly related but for FYI:
Primary light colors are red, green and blue. These three colors can make all colors of the spectrum for screen display.
Primary pigment (print) colors are red, yellow and blue. These colors, when properly mixed can theoretically make all colors in print.
(The break is over, now back to the explanations.)

PRINTED MATERIAL
For printed material, the eye (for some) can see very detailed things down to about a 1000th of an inch. In photos, a 72 DPI picture will look ugly, blocky, and terrible to the naked eye when viewed within 12 to 18 inches. Since a good eye can see sharp details and color differences, photos should be a approximately 300 DPI for fairly descent print. Prints can consist of millions of colors or combination of colors. AS of now, there are numerous printers out with 6 - 8 inks to better simulate as much spectrum of a large color wheel as possible. But for a photo to be printed that will contain all of these colors, ALL of that information must be present in the photo and the kb size of a photo will become larger and larger as more detail and resolution is needed in print. I often print at 600 DPI, and in Japanese, I sometimes print at 1200 DPI.

COMPARING THE TWO. Since printed material generally takes 300 DPI as minimum, and Screen print takes 72, a photo destined for print must be approximately 4 times larger in kb size than a web/screen photo - that is - if both are to be the same physical size such as 4 by 6.

CAMERAs AND THEIR PHOTOS
Some people use their digital cameras for Web Photos/Screen photos only. Some people use their cameras for Print only. And Some use the digital cameras for both. MOST cameras do not know what the photos will be used for, so they are designed to take the photos in the larger size in case the photos are used for print. In this case it is up to the individual to figure out how to get them into a web format.

I know it is confusing as I have been trying to explain it to my wife for 16 years, and haven't done it yet!  

In order to answer the questions that were asked above in the first post, the principles and relationship between screen versus print as they relate to resolution - need to be understood. Not always easy.


A LAW OF PHOTOSs:
Printed photos - need to be 300 DPI (or close there abouts)
Web/Screen photos - need to be 72 DPI (or close there abouts)

THEREFORE - Web/Screen photos are approximately 1/4 the KB size of Print photos to look just as good.
PRINT Photos must be approximately 4 times larger than Web/Screen photos to have the same/similar resolution.

A CAVEAT LAW - You cannot take a 72 DPI photo and make it become 4 times larger to get a good print. You can change a "for print" into a Web photo, decreasing it in KB size without losing overall resolution.


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