What is the best resolution for a web camera?

Digital photograph image resolution

• Am I right in what I say in the next paragraphs? Or, are the opinions of others that I give subsequently more correct than mine? I recently became interested in digital photography and have a done a great deal of reading and research on the issue of image resolution. I have learned that the importance of resolution depends on how one intends to display the image. As an experiment, I photographed the same image at 1, then 5 , then 10 megapixels. When displayed to fit my computer screen or printed on 5 x 7, these images are indistinguishable to my eye, or to others I have shown them to. As another experiment, I photographed a small flowerbed in my garden at 10 migapixels, then took ten separate zoomed photographs of the same subject, which I stitched together using software. The resulting 10 versus 60 megapixel images (after overlap)are indistinguishable to my eye (and those of others)when displayed to fit my screen or printed on 5 x 7. (At full size, of course, the difference is substantial) I understand this as resulting from the image scaling that is required. To print 5 x 7 at 300 ppi requires only 3 megapixels and to display on my 1280 x 1024 screen requires only 1.3 megapixels. However, at a recent camera and photography show, three "professionals" said I was wrong when I suggested that anything more than 3 megapixels seems to be wasted when the image is to be displayed on a monitor or printed small. I was told by one that a 10 megapixel image downsampled to 3 megapixels will look substantially better than the same image taken originally at 3 megapixels. I was told by another that an image displayed on a monitor will show all the original detail even though downsampling occurs. Also, I have read on a professional web site that high definition of an image taken with a large formal camera will "jump right out you" even when displayed as a small image on a web page. I thought I had understood this topic, so I need to know who is right and who is wrong. If I am wrong, I need to understand what I have been missing.

• Answer:

  nosredla-ga: Thank you for your Question. This is one of those situations where the "right" answer is much more of a "it depends" answer than a simple "yes" or "no". For your specific situation, and for how you use your digital photos (ie. viewing them on-screen, and printing them at no larger than 5x7), you are mostly right. The opinions of the 'pros' you spoke with are also mostly right, but again with a large "it depends" attached to them. Here's why. Megapixels are a convenient way for marketing types to try to give consumers an 'easy' way to compare products from different manufacturers. However, just as with tires and their traction ratings (where each manufacturer uses a different test to determine the ratings for their own tires), there's a lot more that needs to be considered than just the number of pixels in the cameras' sensors. Whenever you look at the number of pixels, you also need to consider the size and quality of each of those pixels! Having a lot of small pixels in a small sensor is usually worse than having less, but larger, pixels in a larger sensor, since the ultimate purpose of the sensor is to capture light and convert it into a digital representation. The larger pixels on the larger sensor will be able to capture more light, and more accurately convert it into a set of values corresponding to its color and brightness. The larger size also helps improve the signal-to-noise ratio, reducing the amount of noise in the raw captured image, and hence the amount of post-processing that the camera needs to do to compensate for the noise. Articles that explains all this in much greater detail can be found here: "Beyond Megapixels" Part 1 - http://www.thetechlounge.com/article/121/ Part 2 - http://www.thetechlounge.com/article/123/ Part 3 - http://www.thetechlounge.com/article/134/ "Noise" http://www.dpreview.com/learn/?/Glossary/Digital_Imaging/Noise_01.htm "Noise Reduction" http://www.dpreview.com/learn/?/Glossary/Digital_Imaging/Noise_Reduction_01.htm The "Beyond Megapixels" article also goes into the many other parameters that truly differentiate one camera from another, including the size and quality of the lenses, the quality of the cameras' control systems for focus, metering, and aperture, and of course the post-processing and compression of the image into a digital file format. Remember that the JPEG file format is a lossy-compression file format, meaning that details are lost even as the file is created by the camera after the image is captured. Coming back to the opinions of the pros, it is possible to make their opinions "right", by saying what they depend on... Opinion 1: "a 10 megapixel image downsampled to 3 megapixels will look substantially better than the same image taken originally at 3 megapixels" It depends... on whether we are talking about two images taken with the exact same camera that has a 10 megapixel sensor in it. If we are, then in order for the camera to save the image as a 3 megapixel image, it needs to post-process the raw (10 MP) image. The scaling will result in loss of details, and the amount lost depends on the scaling and filtering algorithm used by the camera's processing system. This is referred to as interpolation loss. While interpolation loss is usually more perceivable when scaling up rather than down, it still happens. After all, if you start out with, say, a 3x3 matrix of values and you need to reduce it down to a single value, there's many different ways to go about it and the end result will not be as good as the original. Now, if you took that original 10 MP image, and scaled it down on a computer where you may have access to more-sophisticated interpolation algorithms, then the end result will indeed look better. However, if we are talking about images taken with two separate cameras, then all bets are off. The 'look' of the image will be more greatly affected by the size and quality of the lens, the size of the sensor, and the rest of the camera features, than by the mere difference in megapixels. It used to be the rule of thumb that only the higher-end cameras (digital SLRs) had the higher megapixel count due to their larger sensor size; however, with recent improvements in sensor manufacturing techniques allowing sensor makers to pack more and more pixels into smaller and smaller sensors, this rule of thumb no longer holds true. Having just recently shopped for a new digital camera myself, I can attest first-hand that a high megapixel camera with a bad lenses, will be a lot worse than a lower megapixel camera with a quality lenses. ========================= Opinion 2: "an image displayed on a monitor will show all the original detail even though downsampling occurs" It depends... well actually, this one is more wrong than right. The typical computer user runs their computer screen at resolutions that result in about 72 to 96 dpi. If the monitor is a CRT-type, then each pixel is actually the end result of physical interpolation of the nearest 'dots' on the screen. If the monitor is an LCD, then it's more likely that there's a one-to-one mapping of pixels to the screen, unless the LCD is having the software-interpolate a smaller screen size up to fill the full panel size, or software-interpolate down a larger screen size to reduce it to fit the actual panel size. In any case, since even a 3MP image will be larger than the typical computer screen resolution, already the image will need to be scaled down in order to fit onto the screen, so the quality of the downscaling algorithm used will ultimately determine what details end up making it to the screen. Now, if this opinion were coupled with Opinion 1, then technically yes, a 10 MP image taken with a 10 MP camera, when compared to a 3 MP image taken with that exact same camera, may have richer details that survive all of the software-interpolation and physical interpolation, and those details may be perceivable to the human eye. ========================= Opinion 3: "high definition of an image taken with a large format camera will "jump right out at you" even when displayed as a small image on a web page." It depends... on whether that camera has a high-quality lens and a larger sensor to go along with the megapixel count. If it does, then there is a good chance it will capture deeper colours, better gradients, and better focus than a 'cheaper' camera, and that all of that will survive the downscaling to the small image on a web page. However, if that high megapixel camera has a compact sensor trapped in a compact camera body behind a distorted lens, then the image will still, well, suck. ========================= Since photography is all about capturing light and recording as much information as possible about that light, bigger is indeed better when all else is equal. Rarely is all else equal, though! That is why every reputable digital camera reviewer out there, uses techniques similar to what you did before you formed your own opinion. They take pictures of a known subject, then visually compare the results to see what their own eyes tell them. Then, they factor in how the images will most likely be used, before stating their recommendations. They know that a digital SLR, for example, will more likely be used by someone who is more 'into' photography than a simple point-and-shoot camera would be, so they hold the dSLR to a higher standard than the simple point-and-shoot. In your case, since you know that you will be using the images primarily for on-screen viewing and smaller-format printing, the only real value to you in taking your photos at a higher resolution than 3 MP, is to allow you the opportunity to crop your images down to 3 MP in the comfort of your own home, rather than trying to frame that perfect shot in the middle of the action. Ultimately, though, never forget that it's about capturing the right light, and that the optical features of your camera (such as a zoom lens) are there to help you capture more of the light you want. Any post-processing features of your camera (including digital zoom) and your photo-editing software, are only there to help you get the most out of the light that you managed to capture. I hope that this helps Answer your Question. Please let me know if you would like me to clarify this Answer, by using the Request Answer Clarification button. Also, please note that there are currently some issues with the e-mail notification feature of this service, so it may take me a day or two to find out about your request and to provide the clarification you seek. Good luck with your hobby! aht-ga Google Answers Researcher