Mount Vernon Computer Club

Digital Camera Basics

January, 2003

Presented by Fred Sgrosso

Tonight we will have a short tutorial which is presented below .


Some of the factors to understand when purchasing a digital camera.

  • Megapixels:
    Resolution or the number of Pixels
  • Lens: (Optical and digital zoom)
  • Camera Size:
    Does size matter?
  • Viewfinders
  • Price:
    Certainly Price is a an important factor when buying a digital
  • camera.

  • Digital Film:
    Various Types
  • Card Readers


Megapixel and resolution
One megapixel (MP) = 1 million pixels. A 1 MP camera at it's maximum quality setting produces images of 1 million individual pixels or dots.

In camera ads you may also see another way to describe the resolution of the camera. A number such as 1152x864 pixels, illustrates how the pixels are laid out on the picture taking device(CCD) within the camera.

This means that the CCD has 1152 pixels in the wide dimension and 864 pixels in height. The total number of pixels= 1152x864 or 995328 pixels. This would describe a 1 megapixel camera.

The greater the number of pixels the bigger and clearer the print will be. It is similar to viewing a picture in a cheap newspaper vs an image in National Geographic. The dots are finer in the better magazine and the picture clearer.




The graph above demonstrates the relationship between the number of pixels and the size of a quality print that can be produced. Also presented is the cost.The cost is for non- interchangeable lens cameras and usually a 2:1 or 3:1 optical zoom and an auto focusing lens.

One pays more for more pixels.

The question that always arises is how many pixels do you need. As usual, the answer is not a simple number. The correct number of pixels depends on the purpose the camera will be used for. For instance, if you want the camera for e-mailing images to relatives or pictures on E-Bay, the requirements are modest. An inexpensive 1 MP camera will do fine. If you want small prints (4x6inch), a 1 or 2 MP camera will suffice. If you want bigger images or like to crop your images, a 3 or 4 MP camera is what you should buy. The 5 and 6 MP cameras are for the more advanced photographers who want the flexibility and all the features that a camera in the $1000-$2000 range delivers.


Lens The next area to think about is the lens. You will see terms like " 2x digital zoom" and "3x optical zoom" for a total zoom of 6/1! WRONG! Just look at the optical zoom figures. If you are buying a camera with a zoom lens ( I would) get at least a 2x optical and preferably a 3x.

The Digital zoom is nothing more than enlarging your image and duplicating the existing pixels to fill the space. You can better do that with your imaging software that comes with most cameras or can be purchased at under $100. A great imaging package is Adobe Elements v2.0 for under $100.

The lenses on the under $2000 cameras do not detach. You can buy screw on accessories to make a fixed mount lens achieve a greater wide angle or telephoto effect. Most often you will see the focal lengths of the lenses quoted in terms of 35mm eqivilents,ie,35-105mm or 7-21mm when using the digital camera CCD dimensions. The numbers mean the same thing and refer to a 3x zoom, which provides a good zoom ratio to physical size.

The f# is a way to measure the light gathering ability of a lens. The SMALLER the number the more light the lens gathers and the size and price go up. Most of these cameras have f#'s of 2.8 at the wide angle end and f5 or so at the telephoto end. The faster the lens the less often flash is necessary, and the higher the shutter speed can be. This is only important on dark days and dark places where you do not want to use a flash.

The purpose of explaining about f# and focal length, is to help understand why you can pay the same amount for a full featured 2 MP as for a bare bones 3 MP camera. One camera may have no zoom vs. one with a 3x zoom and or a faster lens. Macro or close-up capability will also be a cost determining factor.


Viewfinder
Some cameras are sold today without an optical viewfinder. In my opion that is not a good thing. It means you have to use the LCD viewer as a viewfinder which is often hard to see and use batteries like crazy. Get a camera with an optical viewfinder.
Price: Roughly you can figure $100/MP up to 3 MP. The price varies considerably with the lens and the size of the camera purchased.
Size:
Size is important to some folks. The credit card size camera are more expensive because they are tiny. You will probably get a small zoom lens because it is hard to package a lens with a large range in a small package.

Digital Film

Digital "Film" pays for itself over time:You can fill the card up with images and then download them into your computer and then start all over again.

  • Many types of memory cards

  • Mini CD, Floppy Disc, Memory Stick (Sony)

  • Smart Media and Compact Flash(CF) Cards-Probably most popular

    Fuji has the XD card..very small, and shows much promise.

    Secure Digital and Multi Media cards have been added to the mix.

  • Comes in different amounts of memory-more memory=more cost but also more pictures can be stored for later viewing

  • 8MB card stores about 16 images for a 2mb camera with jpg compression set for HQ Mode
  • 64mb=128images...more images if more compression is used and less if camera is a higher megapixel camera.

  • Cards can be bought up to 1GB capacity..

I like the Compact Flash (CF)card. It has universal acceptance and will be around for a long time. All the professional cameras use the CF card.
Card Reader A card reader is useful to download the images from the card w/o being tethered to the camera. It also saves the batteries in the camera.


Some Thoughts:

Paper and ink costs have to be figured when comparing costs of conventional film+processing to that of digital print

Digital images can be sent to labs for conventional prints if you do not want to print them.

Time spent learning new software has to be considered too.

X ray problem with Film goes away..


Recommendation for a mid range camera.
I would buy a 3 megapixel camera with a compact flash card, a 3x zoom, an optical viewfinder, and a configuration that nicely fill your hands. Canon (my favorite), Nikon, Minolta, and some Kodak models fill these criteria. Kodak has a neat docking package that gives you the extra batteries and card reader in a very convenient package. Every company has a nicety that only you can determine whether those special features are useful to you. This package will cost around $300.


Photo by Marty Foley

The above image is an example of an image produced by a good 2 megapixel camera.

The camera is a Olympus Model D-510

Note the clean whites and some detail in the whites, along with good color and no noise in the shadows.

Overall, a very good reproduction of the Mt. Vernon Clubhouse.

Note size of image is TV format-4:3 or 1.33 ratio of width to height-- 35mm is 1.5:1 ---therefore a 4x6 inch print fits the format perfectly The above image would print out as a 4.5x6 inch print : so some cropping is necessary to get the same format as 35mm.




PRINTER

* The printer can be adjusted for high resolution printing which yields good quality images and much slower output.

* Glossy or 'Photo' paper should be used and preferably the paper should be the manufactured by the same company as the printer.

* The ink should be made by the printer manufacturer also.

My favorite photo printer manufacturer is EPSON. The Epson 785 EPX Has good reviews..around $200..and can take all digital film and has an optional color LED screen for viewing. The Epson Stylus Photo 820 is a 6 color printer and is around $100 with rebate.

SCANNERS

Flatbed scanners can be bought with film scanning capability...Epson makes good ones for $300. The best results are obtained with film scanners, if you are scanning 35mm film..slides, negatives, black and white or color. They are more expensive. $1000 for a good one. Flatbed scanners can be bought for $100 and are great all around work horses.

The scanner should be set for 200-300dpi/inch scan resolution for the output size print desired.

Setting the scanner for higher resolutions wastes file space and no improvement in the print quality is obtained...

For a 4x6 print- 4x 300= 1200 pixels

6x300= 1800 pixels

Total pixels=1200x1800=2 megapixels

File size when opened or if using tif formatting= 2megapixels x3 colors=6mb

When scanning an 8x10=20mb (uncompressed). Using 200 dpi/inch would probably work well if file space is a factor.

When scanning a black and white document-use greyscale-which cuts the file size down by 2/3, because only one color is used. For an 8x10, the file size would be 7mb before compression.

JPG file size=100-400kb, depending on the compression---(best -good-fair) Compressing an image..a blue sky compresses easily and trees do not.. more compression gives more errors in the final picture, jagged edges etc..

For e-mail...70-100 dpi resolution is recommended so that the image opens quickly, the monitor cannot resolve higher resolutions...

Do not get confused about printer dpi(dots/inch) and ppi(pixels/inch).. DPI is for the printer only...more dots give better resolution...sharper appearing images, unfortunately scanners are rated in dpi and that is where the confusion sets in. They should be rated in ppi, but are not.

PPI is related to the image..more pixels help up to a certain amount..300ppi is the maximum amount a inkjet printer can print..even if the dpi is set for 1240dpi.

The two numbers have no relationship to one another..

Too many dpi and the printer slows to a crawl for large images and no improvement can be seen w/o a magnifying glass.

With a scanner, too much dpi gives huge files that waste space and are impossible to work with or send.

Setting a scanner to scan a 4x6 image at 2400 dots/ inch will give you an unmanageable file of over a 100mb...vs a file of 6mb uncompressed. Using JPG compression on the "best" setting will usually yield excellent results and reasonable file sizes. This also means more room on your digital card for storing images..

Image processing software:

The best image processing software is made by Adobe. PhotoDeluxe and Photoshop Elements are two good ones. Photoshop 5.0 LE comes free with many scanners and is excellent too. We will demonstrate Photo Deluxe quickly tonight because it is a freebie with many cameras and scanners.. The full blown Photoshop 6 is very expensive and too complicated for most.

Main points...

* Reducing or increasing image size

* Uses 'layers' for ease or image manipulation

* Color correction

* Cropping

* Red Eye Elimination

* Changing picture format-ie, from bmp to jpg or tif and vice versa

* Borders around images

* Adding text to images

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