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Pixel color depth or bits per pixel in digital photos by Ziv Haparnas

Digital photos are built of many pixels. Each pixel has a unique value which represents its color. When you are looking at a Digital Photo your eyes and brain merge these pixels into one continuous digital photo. Each pixel has a color value that is one out of a finite number of possible colors this number is known as color depth.

Each pixel has a color value that is one out of a palette of unique colors. The number of such unique potential colors is known as color depth. Color depth is also known as bit depth or bits per pixel since a certain number of bits are used to represent a color and there is a direct correlation between the number of such bits and the number of possible unique colors. For example if a pixel color is represented by one bit - one bit per pixel or a bit depth of 1 - the pixel can have only two unique values or two unique colors usually these colors will be black or white.

Color depth is important in two domains: the graphical input or source and the output device on which this source is displayed. Each digital photo source or other graphics sources are displayed on output devices such as computer screens and printed paper. Each source has a color depth. For example a digital photo can have a color depth of 16 bits. The source color depth depends on how it was created for example the color depth of the camera sensor used to shoot a digital photo. This color depth is independent of the output device used to display the digital photo. Each output device has a maximum color depth that it supports and can also be set to lower color depth (usually to save resources such as memory). If an output device has a higher color depth than the source the output device will not be fully utilized. If an output device has a lower color depth than the source the output device will display a lower quality version of the source.

Many times you will hear color depth expressed as a number of bits (bit depth or bits per pixel). Here is a table of common bits per pixel values and the number of colors they represent:

1 bit: only two colors are supported. Usually these are black and white but it can be any pair of colors. It is used for black and white sources and in rare cases of black and white screens.

2 bits: 4 colors are supported. Hardly used.

4 bits: 16 colors are supported. Hardly used.

8 bits: 256 colors are supported. Used for graphics and simple icons. Digital photos displayed using 256 colors are of poor quality.

12 bits: 4096 colors are supported. It is hardly used with computer screen but sometimes this color depth is used by mobile devices such as PDAs and phones. The reason is that 12 bits color depth is the limit for high quality digital photos display. Less than 12 bits screens distort the digital photo colors too much. The lower the color depth the less memory and resources are needed and such devices are resources limited.

16 bits: 65536 colors are supported. Provides high quality digital color photos display. This color depth is used by many computer screens and portable devices. 16 bits color depth is sufficient to display digital photo colors that are very close to real life.

24 bits: 16777216 (approximately 16 million) colors are supported. This is also known as true color". The reason for that nick name is that 24 bits color depth is considered more than the number of unique colors our eyes and brain can see. So using 24 bits color depth provides the ability to display digital photos in true real life colors.

32 bits: in contrast to what some people believe 32 bits color depth does not support 4294967296 (approximately 4 billion) colors. In fact 32 bits color depth supports 16777216 colors which is the same number as 24 bits color depth. The reason for 32 bit color depth existence is mainly for speed performance optimization. Since most computers use buses in multiplications of 32 bits they are more efficient using 32 bits chunks of data. 24 bits out of the 32 are used to describe the pixel color. The extra 8 bits are either left blank or are used for some other purpose such as indicating transparency or some other effect.

This article can be published and used as long as the resource box including the backlink is included. Mr. Haparnas writes about science and technology. More information on digital photo printing and photography is available on printrates.com - a site about digital photo print service Ziv Haparnas is an expert in technology.

Article Source: http://www.earticlesonline.com/Article/Pixel-color-depth-or-bits-per-pixel-in-digital-photos/69021

Which is better a high pixel or changable a lens?

I have to make a choice between a 10.1 pixel camera without the option of changing the lens or an 8.1 pixel that can?... Any camera reccomondations $500 or less?

A make and model would help, but the 8.1 camera is undoubtedly a digital SLR - probably a Canon EOS Rebel XT.

There are no Fixed Lens cameras that I know of that have more than a 1/1.8-1/1.7" sensor, which is about 38 sq. mm. The XT has a much larger sensor at 328.6 sq. mm. The sensor size in the SLR will give you MUCH better image quality.

Check this out: http://www.flickr.com/photos/samfeinstein/476181751/

Okay, the SLR is 10 MP, but you will see so much difference that I think you can practically discount that. The SLR gives much more definition.

$500 or less??? I like the Nikon D40 for $525. A comparable Rebel XT is $565. (Both with the 18-55 lens) The Pentax K100D is $550 with the 18-55 lens.

My choice of these three would be the D40, regardless of price.

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Nikon D40 vs. Canon EOS 350D (Rebel XT)

This isn't exactly what you asked for, but perhaps you will find it helpful in making your decision. I have never used a Canon EOS 350D, so I can't actually compare the cameras, but I favor the D40 because it has a spotmeter and the 350D doesn't. Although the D40 seems small, it is practically the exact same size as the 350D.

http://www.dpreview.com/reviews/compare_post.asp?method=sidebyside&cameras=canon_eos350d%2Cnikon_d40&show=all

http://www.dpreview.com/reviews/nikond40/page17.asp

tells us that the Canon 350D meter calibration is off by about 1/3 of a stop. This would not really present any problems, except that it suggests "something" to me about the quality, since the Nikon and Pentax are dead on.

Scroll on down the page for image comparisons. The D40 is clearly sharper and shows less noise at all ISO settings.

http://www.dpreview.com/reviews/nikond40/page18.asp shows us that both handle shadows equally, but the D40 clips the highlights by about 1/3 of a stop.

http://www.dpreview.com/reviews/nikond40/page21.asp shows a side-by-side of studio images. The 8 MP of the Canon 350D at least put the camera on equal footing with the Nikon D40 for image quality, but you have to take note that the Rebel XT is shot at ISO 100 and the Nikon is shot at it lowest setting of ISO 200. I think the Canon images may look a little better, but we know from the prior page that under equal lighting levels, the Canon will start to break up before the Nikon.

The reviewer says, "While it is possible to pick areas of the image which lend some credence to the EOS 350D's 34% pixel count advantage it's clear that the average observer would not notice these differences and that you would need a very large output size for any of them to become visible."

Check this out...

http://dpreview-img.fotki.com/gallery/canoneos350d_samples1/originals/img_4068-raw-dpp.jpg is taken by the Canon 350D with a 17 mm Focal Length at f/6.3, 1/80th of a second, ISO 400 using RAW.

http://dpreview-img.fotki.com/gallery/nikond40_samples/originals/dsc_1206.jpg is taken with the Nikon D40 with an 18 mm focal length at f/4.5, 1/80th of a second, ISO 400 using jpeg.

The point of focus for the Canon photo is a bit deeper than it is for the Nikon, but even having 8MP and using RAW and a smaller aperture, I think the Canon image breaks up a lot more than the Nikon. You can barely make out the features on the face of the gentleman in the background. Is this the camera or the superiority of the Nikon 17-55 lens, which so many of us here praise???

Okay, I've made my stance clear. I like the Nikon D40 better than the Canon EOS 350D, so here's my general review of the D40.

The Nikon D40 is a great little camera, very easy to use and quite reasonably priced. It has a few "consumer friendly" totally automatic modes that make it very easy to use, but still offers total photographic control when you are ready to take charge. It will get you in the Nikon family which is a great place to be. If you buy accessories and lenses, you will be able to use everything on any Nikon that you might upgrade to later on.

Check out Nikon's "Picturetown" promotion, where they handed out 200 D40's in Georgetown, SC. http://www.stunningnikon.com/picturetown/

Here are a few reviews, in case you have not read them yet. Be sure to note that they are several pages long and some of the reviews also have some sample images that you can look at.

http://www.dpreview.com/reviews/nikond40/

http://www.steves-digicams.com/2007_reviews/nikon_d40.html

http://www.popphoto.com/cameras/3756/camera-test-nikon-d40.html

http://www.kenrockwell.com/nikon/d40/d40-recommendations.htm

I hate to see people slam the camera because it can't autofocus with older Nikon lenses. It is true that there is a "slight problem" with older Nikon lenses not autofocusing on the D40, but if you do not own a bag full of older lenses, it is not going to be a problem. It is barely a problem anyhow. If you check www.nikonusa.com for "AF-S" lenses, which are ALL 100% compatible with the D40, you will find 23 lenses, including 7 "VR" (vibration Reduction) lenses and one true macro lens with "VR". There are another 25-plus lenses in the current catalog that provide all functions except autofocus as well as many (possibly dozens) "out of print" lenses that will work just as well. In addition, although these lens will not autofocus, most of them will still give focus confirmation. From the D40 manual: "If the lens has a maximum aperture of f/5.6 of faster, the viewfinder focus indicator can be used to confirm whether the portion of the subject in the selected focus area is in focus. After positioning the subject in the active focus area, press the shutter release button halfway and rotate the lens focusing ring until the in-focus indicator is displayed." (See http://www.members.aol.com/swf08302/nikonafs.txt for a list of AF-S lenses.)

The D40 only has 3 autofocus zones arranged horizontally at the center, 9 o'clock and 3 o'clock positions. This might be considered a limitation, but realistically, most people will find this perfectly adequate, especially if you are moving up from a point and shoot with only a center zone.

You can get the D40 with the 18-55 kit lens at B&H Photo available through Yahoo! Shopping or at 1-800-622-4987) for $525 (June 2007). Add a Lexar Platinum (60X speed) card for $25 or 2 GB for $35. Or - get the D40 with 18-135 lens and 1 GB Lexar card for $750. They also have used D40's from $475.

And yet... clearly these are both very good cameras. What it all comes down to is which one YOU feel better about. Go to a camera shop and pick them up and see.

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Nikon D40 vs. Pentax K100D

I was devoted to Pentax film cameras for most of my life. They have just started to come on strong in digital camera development, but Pentax has always been a concervative company, in my opinion.

Others make the point that you should choose a camera system by its lenses and this is definitely true. Both Pentax and Nikon have a full catalog of lenses to choose from, although fhotoace points out that it may be harder to find good used Pentax lenses. Finding used Nikon lenses will not be a great help for you if you buy the D40, as most will not autofocus with the camera. It requires the newest generation of lenses, the AF-S lenses for auto-focus. However, most of the older lenses will still work perfectly well in all other functions. Most will even give you focus confirmation as you focus manually.

The Pentax has built-in image stabilization, but as far as I can determine, it is only one mode. Nikon offers some "VR" lenses that have two modes of image stabilization to be used under different circumstances. I admit that this is still an advantage for Pentax, though.

I have two stock answers that I will spare you reading, as the real decision here is how the camera feels in your hands. Since you have some camera experience, you will know what to look for. Go to a camera shop and ask to handle each camera. Ask how each one would be put into the different modes. They each have a mode dial, but once you are in shutter or aperture priority of manual mode, see what you have to do in order to actually adjust the shutter speed or aperture. Frankly, I'd like to see a few more buttons on either camera so you would not have to dive into the menu system to make changes, but I guess that's part of being "entry level."

From the spec sheets, it concerned me that the Pentax uses "AA" batteries. I didn't know that until now. True, you can use NiMH rechargeables, but dpreview said that they have gotten "many hundreds" of shots out of dispoable lithium CR-V3 batteries, so I guess that is not an issue.

For an SLR, this quote from the dpreview page also concerns me: " K100D is acceptably quick in most everyday respects but doesn't feel as snappy as you would expect from a modern digital SLR. The biggest disappointments would probably be the lack of instant startup, relatively sluggish record review and a virtually pointless continuous shooting mode (just four JPEG frames)."

My usual pitch is to say that the Pentax K100D is the cheapest digital SLR worth owning and the Nikon D40 is the one I would choose for myself. I would stand by that decision after some review on your behalf tonight.

Check out this comparison page. Click on "In-depth review" and "Read Owner Opinions" for each camera. Be sure to note that the reviews are many pages long so you don't stop after page one. Check the sample images, also. You can enlarge these to full size images if you click on the file name shown below the picture. You will have to then put your cursor in the white space to the right of the picture and click once. After that, you can pass your cursor over the image and it will turn into a magnifier. Click it as a magnifier once and the image will go to full size and you can really examine the detail or look for artifacts like purple fringing around items in high contrast photos or noise in darker areas of the picture.

http://www.dpreview.com/reviews/compare_post.asp?method=sidebyside&cameras=pentax_k100d%2Cnikon_d40&show=all

Fortunately, these cameras came out at about the same time and both reviews compare one camera to the other in many aspects. This will help you with your decision.

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This entry was posted on Saturday, October 18th, 2008 at 1:57 am and is filed under Surveillance. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.