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Thread: Pixels in digital cameras vs. Grain in film

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    BillTexas's Avatar
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    Pixels in digital cameras vs. Grain in film

    There must be someone that has compared the number of pixels to the number of grains for a particular film. I was told that a 35mm negative is the equivalent of 20MP. There must be some variation depending on the film.

    Does anyone know where that information is?

    I'm reading Digital Photography for Dummies and they are saying that more pixels do not necessarily mean a higher quality image. I don't understand why. With film, the smaller the grain, the better the image that we got. For an old example, I got better enlargements from Panatomic X than Tri-X when I made really big ones.

    If what they say is true, then I should keep the values down on my G10 (14.7MP) instead of using the finest setting. And what about raw, which uses all megapixels but is supposed to provide the best image to work with on the computer.

    The question about Donald Duck has been bothering me, too, but I'm just going to let it go.

    Thanks.

    BillTexas.

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    Davey's Avatar
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    Re: Pixels v. Grain

    I could be wrong but I'd assume the more = better thinking is to do with the way the sensor actual works. Yeah higher res sensor is fine but if you shrink the size of the pixel down then you also shrink how good they are at collecting light info for that point. See the tutorial section for more info, particularly

    http://www.cambridgeincolour.com/tut...ensor-size.htm

    I'd imagine shooting in a lower mode is a waste of time, as far as this effect goes since you have the same sized sensor still, just only save info from some of them. As for raw again the tutorials can shed more light on the topic better than I can explain. Basically to cut a long story short it's more to do with more control over how to interpret what the sensor captured rather than completely leaving the interpetation to the camera. The only down side is size of file as no info discarded and processing time rather than instant result.

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    Daniel Salazar's Avatar
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    Re: Pixels v. Grain

    Hi Bill

    What you ask is one of the these existing Myths that nobody corrects and they are still around us. Of course, thanks to this Myth I was able to buy a camera with 14.2 Megapixels

    Pictures are made up of little dots called pixels. The picture is made with enough of them together arranged horizontally and vertically.

    If you get close to an image or use a magnifier you'll see them.

    I got the following example in Wikipedia to explain it:


    The picture of the left gives you the example on how you could see an image with a magnifier glass and depending on your distance to the image you'll see it clearer.

    The same happens with the size. Depending on how big you want your picture, you will need a picture with more Megapixels, therefore if you want a 2.1" x 1.6" picture, you don't need a camera able to take 24 Megapixels or something like that.

    Final Print Size Megapixels Image Size on Monitor
    2.1" x 1.6" 0.3 640 x 480
    4.25" x 3.2" 1.2 1280 x 960
    5.3" x 4" 2.0 1600 x 1200
    6.8" x 5.1" 3.0 2048 x 1536
    10" x 6.5" 5.3 3008 x 1960
    10.25" x 6.8" 6.3 3088 x 2056
    13.5" x 9" 11.1 4064 x 2704

    Here is what we name resolution, which refers to the size of the image that your camera will produce, so if you have e.g. a 2.0 Megapixels camera and you print a picture as a poster, then you will get a print with a lot of big dots as on the left picture showed above.

    To figure out the amount of megapixels that will give you, you multiply the dimensions.

    For example:
    1600 x 1200 = 1.92 million pixels or 1.92 Megapixels. This would commonly be rounded up and referred to as a 2 megapixel camera.

    As this amount goes higher, you will notice a much sharper image, so then....more pixels don't mean better quality, everything depends on the size and the distance.

    I hope it helps!

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    Davey's Avatar
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    Re: Pixels v. Grain

    also a lot of pixels just give a bit more to crop. The whole megapixel marketing thing is rubbish, ie the difference between a 6MP and 8MP seems massive but it's just a bit more vertical res and a little added to the horizontal which doesn't make much of an improvement overall. Doubling it does so 6MP to 12MP really is twice as much an area. I can blow my 5MP stuff up without issue even at close-ish viewing, obviously it won't do 40" print that stands up to scrutiny for 6" away viewing.

    It's bad is compacts because of the size issue since the sensors are small and often 5MP is the same size as 12MP and etc but they cram more pixels into that space. Due to small sensor the pixels are none to great at collecting light info hence the increase in noise (my camera is terrible for it where as an equal MP dSLR with much bigger pixel sensors would be same res image but higher quality even without lens considerations just the sensor alone). Again the tutorials here and various places around have realworld comparissons and proof of this.

    I could be wrong but I think the limiting factor in quality is the technique and composition coupled with sensor size. Eg1 a crystal clear well composed 8MP shot will look better blown up past the expected size said by marketing hype than an out of focus poor 16MP would blown up the same. Eg2 at small sensor sizes, in an equal compact with just sensor size changing the 8MP might produce a better image than the 12MP if equal in all other regards from exposure to sharpness due to there being less noise.

    High MP has it's uses but it's not the be all and end all it's made to be, it's used as a stand alone overall comparisson of camera performance value by marketing agencies to sell, like using single value comp related figures like taking cpu GHz alone when a lower value sock F 8360 opty will murder a Phenom II X4 920 (if you know those cpus you'll know I MEAN murder a million times over despite the fact numbers wise you can make the home market desktop/gamer cpu of a tenth the price sound bigger and better). Or graphics cards 9500gt 1Gb mem is better than 8800 512Mb mem due to numbers when the reverse is true. Real world isn't that simple.

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    Re: Pixels v. Grain

    Well instead of worrying why my spit is thin sometimes and thick othertimes, I just go out and take photos.

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    Administrator Colin Southern's Avatar
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    Re: Pixels v. Grain

    Quote Originally Posted by BillTexas View Post
    There must be someone that has compared the number of pixels to the number of grains for a particular film. I was told that a 35mm negative is the equivalent of 20MP. There must be some variation depending on the film.
    Hi Bill,

    They say that "truth is the first casualty in any war" - and this is one of those topics where objectiveness has been heavily biased depending on what position one was trying to defend.

    I don't want to get too involved in the debate, but ...

    1. Grain -v- Pixels can't be directly compared (accurately) as the limitations of differing amounts show up in different ways.

    2. With regards to sensor resolutions, I think it's smart thinking to keep a camera set to the maximum as (a) memory is dirt cheap these days and (b) it can give you far more cropping options. Depending on the size of the print, you can easily hit a point of diminishing returns for small prints with a modest MP camera, but the differences show as the print size grows. It's a square-law thing though; to double the resolution you need to double the pixel dimensions IN BOTH AXIS - so to double the resolution of a "lowly" 8MP camera you'd need a 32MP camera, so in this respect all the bellyho of the MP race is vastly over-rated.

    You CAN reach a point where optical effects like diffraction render increases in MP count pointless, but as a rule the quality deterioration of a captured image (from the theoretical perfect capture) is an accumulative (although not necessarily proportional) thing. Think of starting with the perfect theoretical capture then degrade the quality by X amount for camera shake / lens quality / diffraction / MP count / anti-aliasing filter / demosaicing process etc etc etc.

    In my opinion the differences in exposure technique between film and digital have a far greater effect on the final quality of the capture (with film you expose for the shadows and process for the highlights, whereas with digital it's the other way around).

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    Re: Pixels v. Grain

    A few years ago I read a report on a site that said Kodachrome 64 35mm slide film was about 50-60 mgpxl., and it depends on the speed and grain of the film. I believe Kodachrome 25 was the finest grain 35mm ccolor film ever made. I shot K-25 & 64 for years and it is just amazing to see how big you can project the images from both. I've been shooting Pro now for over 35 years and use a Nikon D2xs and D100 now but I have a customer who has a car collection and wants me to shoot all the cars but he wants them on slide film. So,,,I guess I need a few rolls of Velvia 50 and my old F4 for the job.
    It will be interesting to see the pic's side by side ,,,12.2 mgpxl DX ISO 100 and 35mm Velvia 50 ISO !

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    Re: Pixels v. Grain

    Quote Originally Posted by BillTexas View Post
    There must be someone that has compared the number of pixels to the number of grains for a particular film. I was told that a 35mm negative is the equivalent of 20MP.
    I think there are many, many more individual grains in a 35mm frame of film than there are pixels in any currently available 35mm DSLR sensor. But quantity apparently isn't everything. It's my opinion, and I think it's a common one, that with ISO 400 or slower prints from 8mp APS-C easily match or beat prints from 35mm film for perception of sharpness and fine detail. Beyond ISO 400 digital wins hands down. Fine grain 35mm film probably has more resolving power, but all that grain gets in the way.

    http://www.clarkvision.com/imagedetail/film.vs.digital.summary1.html



    Quote Originally Posted by BillTexas View Post
    I'm reading Digital Photography for Dummies and they are saying that more pixels do not necessarily mean a higher quality image.
    Once again quantity isn't everything. More pixels may add to resolution, but larger pixels may have better color and more dynamic range. In bright, even daylight a 12mp compact (small sensor/pixels) camera might hold it's own against an 8mp DSLR (large sensor/pixels), but in a low light or high contrast situation the DSLR will be significantly better.

    It also depends on how the pixels are used. Most digital cameras are a single layer of pixels with a Bayer pattern for color. In that case each pixel counts towards resolution. But there is other technology. Foveon sensors use 3 layers of pixels stacked on top of each other for color; this means resolution is actually megapixels divided by 3. All megapixels are not equal.

    Quote Originally Posted by BillTexas View Post
    If what they say is true, then I should keep the values down on my G10 (14.7MP) instead of using the finest setting.
    No. Lowering the resolution in the camera isn't going to help you. That's a software adjustment. They are talking about a hardware adjustment, such as going from a 15mp small sensor to a larger, but lower res sensor like what's in DSLRs. I would shoot at the highest resolution unless storage space is an issue. You can always lower the resolution using processing software.

    Quote Originally Posted by BillTexas View Post
    And what about raw, which uses all megapixels but is supposed to provide the best image to work with on the computer.
    The difference between the raw and jpeg settings is that when you have your camera set to raw you are getting as much of the original info as possible. When the camera is set to jpeg it still shoots raw, but the processing begins with the in-camera software. The advantage to using raw is that the out-of-camera processing software, such as Photoshop, is more sophisticated and offers more control and options. Not all photographers need or choose to use the flexibility of raw. A comparison with film might be raw is like unprocessed print film: all the souping and printing has yet to be done. Jpegs are like processed slides: some tweaking is still possible, but basically they are pretty much finished. Unless you direct the camera to save the raw file it's not possible to retrieve information that the in-camera processing has discarded.
    Last edited by Henry Peach; 16th February 2009 at 07:42 PM.

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    Re: Pixels v. Grain

    To sum up Raw, sooner or later you will be in front of your computer and be in a situation that makes you realise that if you had shot in Jpeg you would have been in trouble. Until that happens you will never be convinced of the benefits of shooting Raw.

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