Naked Science Forum
General Science => General Science => Topic started by: Karen W. on 10/08/2007 16:22:18
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Exactly what is the difference in a printers ability to copy a picture as compared to a camera...? Is it code rather then light reflection etc. or both or neither???
I do not understand cameras exactly either!
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What do you mean by a "printer"?
Printers cannot copy, they can only print; but if you are talking about an "all in one" that combines the functions of a printer, scanner, copier (and maybe a fax), then that is something else. If it is the latter, then it is really the scanner function you are talking about, since that is the part that perceives the image.
There are similarities and differences between a scanner and a camera.
Both a scanner and a camera contain light detectors that convert light to electrical signals.
The first difference is the a camera has a grid array of sensors. For instance, my rather antiquated Minolta S414 has a grid of 2272 x 1704 light sensors, so it can instantly form a rectangular image of 2272 x 1704 dots. By contrast, a scanner a long strip of sensors, so it can at one instance only form a single strip of the image, but it moves that strip along the length of the object being scanned (that is why it is a scanner) so that it can slowly build up the image. This allows the scnner to form a far more detailed image, but using fewer light sensors to do so; but while the camera might take a picture in a millisecond, or at most, likely to be in a small fraction of a second (you can do night shots that take 30 seconds, but they are the exception rather than the rule), but because the scanner needs to slowly build up the image, it can take 20 seconds or more to scan a perfectly ordinary image, and none would be under one second. There are also many other ways that a camera is designed to be more flexible, such as in its ability to focus on real life object rather than only focusing on flat objects, and in being able to use a wider range of light sources.
The printer portion of an 'all in one' device merely puts ink on the paper, and it does not care whether the image it is printing originally came from a camera or from a scanner, or was electronically created from nothing at all.
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I guess I had some funky notion no idea how a printer alone works in comparison to a camera! so the printer doesn't take a picture but surely it receives some kind of code to form the picture it prints... Oh dear George I really don't understand how either one works and if there are any similarities!
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There is an essential difference between your camera (and your TV screen or computerscreen) on one side and your printer on the other : putting it simply adding the basic colours in your camera or screen creates white because your camera analyses the colours according to the RGB method (red green blue), your screen renders the colours the same way so that addition of red + green + blue results in white.
Your printer works with substraction. The basic colours are magenta, cyan and yellow. Each of this pigments absorbs part of the light and the sum of the three means that all colours are absorbed and you see black.
While your screen recreates the colours as analysed by your camera, your printer prints the complementary colours and in the resulting image the rest is absorbed.
I'm afraid wikipedia explains it better than I can without expanding too much.
Start with http://en.wikipedia.org/wiki/Color_theory#Color_abstractions to compare the two.
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The printer receives electronic signals (usually from a computer, although in the case of an 'all in one' printer/scanner, or might be directly from the scanner; or in some modern printers, they can receive their instructions directly from a camera); and the signals instruct the printer exactly where it should put ink on the paper, and the printer simply does what it is told (unless it has run out of ink, or run out of paper), and places that ink where it is told to place it on the paper.
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OK.. It is way different then how a camera takes a pictuer.. Thanks George!
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This brings me to an other question. I happen to have lots of 35 mm negatives and colour slides, so if I want to scan them in, can I compare the resolution I get with the "megapixels" from a digital camera.
To keep things esay, say that the format of a slide is 1 inch by 1.5 inch (24 by 36 mm is about 6 % less both ways) and that I get a scanner with a resolution of 3600 dpi. Would that give 3.6 times 5.4 megapixel or would I have to take more than 1 scannerpoint for 1 camerapixel ?
If I can get about 15 megapixel from my negative plus scanner, why trade in a good old "analog" camera that works even when the batteries are death for something digital ?
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You Know Eric I did notice on my scanner it has a spot to insert a negative but I have no idea how to use it..LOL i should probably get out my manual and check it out. That is a very good question!
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If you are doing lots of scanning of negative, the ideally you should use a negative/slide scanner - e.g.:
http://www.plustek.com/product/series.asp?s_id=4
or:
http://www.europe-nikon.com/family/en_GB/categories/broad/5.html
You can get attachments for using ordinary flatbed scanners (the kind of scanner you normally use to scan printed images, text, etc.), but I suspect it will be suboptimal. You cannot (and I imagine Eric is aware of this, so this may be more for Karen's benefit) just just place a film onto a flatbed scanner without the attachment because flatbed scanners are designed for using reflected light (i.e. they shine a light from below, and look at the reflection of that light off the paper), while transparencies and negatives are intended to be backlit, and don't work well if you just use reflected light.
My expectation is that a decent negative scanner will create every bits as good (if not better) image than any consumer or prosumer level digital camera (ie. if you are willing to spend several thousand pounds on a professional level digital camera, it might yet be better). I suspect that some of the colour films also give better colour accuracy (although this would anyway be lost in the conversion to digital format).
There are still advantages of convenience of direct digital recording, which allows you to change ISO on a frame by frame basis, rather than having to change films to change ISO. Digital also has the convenience of being able to see the image immediately (and retake immediately if not satisfactory), as well as not having the hassles of chemically processing film (or waiting for someone else to do that), and not being restricted to taking images in batches of 36. There are lots of other flexibility and convenience benefits to direct digital recording, but with a decent film scanner, I don't believe that image quality will be one of them.
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As a firm believer in empirical study I picked up my printer....gathered the family and asked them to smile whilst I held the printer to my eye.
Result ?.......no exposure and a family reaching for the phone for psychiatric assistance !!
With the camera ?..I got a piccy !!
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The question was a bit academic. I can not afford to spend thousands of euros (let alone pounds) on a digital system camera, if I can not use my "old" lenses on it. And then I have to deal with the effect of the smaller picture size. A "standard" lens 50 mm focal length would give a picture that I associate more with an 80 mm "portrait" lens.
There are situations where I prefer my digital "consumer" camera for convenience, but e.g. for sporting events I prefer an analog either single lens reflex or coupled rangefinder camera, mainly for the possibility of manual focusing and folowing a moving subject so that the subject is sharp and the background is blurred. But so far, I scanned in the prints for digitalizing.
Anyhow, my analog SLR and CRF cameras are not facing complete retirement yet.