Do you agree with this statement?
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Old 07-26-2005   #1
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Default Do you agree with this statement?

I found this advice in a list of tips at a photo paper website:

"Pixels don't treat all objects equally. About the worst thing you can photograph with a digital camera is a tree. If the camera captures about a million pixels, and the tree contains a few hundred thousand leaves, you end up with three or four pixels per leaf, so it all smears together in a big, gummy mess. The same goes for lawns, gardens, distant mountains, hairy surfaces, or anything else with scads of intricate details. For the best results, photograph clearly defined subjects with smooth, distinct outlines. People photograph well, as do cars, buildings, furniture, and most man-made objects. Stick to obvious foreground subjects that stand out clearly from their backgrounds, and you should be fine."

The interesting thing about it is that I found the opposite to be true when I have photographed my dog-- I was really "wowed" by the detail in the dog's fur that I could see with my digital shots. Way more detail than I would have gotten with film.

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Old 07-26-2005   #2
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Default Re: Do you agree with this statement?

If you really want to get a good idea of the camera's resolution, you shoot a picture with many items in it, such as a large group of people. Shooting just one subject with even a three megapixel camera will look fine.
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Old 07-26-2005   #3
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Quote:
Originally Posted by th0t
Hi ditto1958,

But the notion that a digital image sensor has a resolution limit and film does not is patently false. Film does have a resolution and its called the "grain". There are high-end image sensors that way outperform traditional film when comparing "resolution".
Capture a tree with a Sinar 4x5 sensor and it'll far out perform any film format on the grounds of resolution.
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Old 07-27-2005   #4
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Yes and no.... In theory it's correct that the more detail you have the more resolution you need to make larger than default prints. By default I mean that when a print density is selected in dpi (300 is commonly used for many professional print engines) they the horizontal and vertical pixel counts are divided by this desired print density (300 in this case) and you then have the "native" or uninterpolated maximum print size. As an example, a two megapixel sensor will generally produce a file matrix of 1600 pixels wide by 1200 pixels tall. Dividing by 300dpi on each side we end up with 5.33 by 4.00 inches. So without any interpolation a two megapixel sensor would do a great job at 300 dpi of printing a 3x5 inch image.

But once we begin to enlarge this image we realize that there may indeed be areas of detail where insufficient sampling sites (sensor pixels, if you will) were available to properly define. At a print size of 3x5 inches these poorly defined details (let's call them "marker pixels" because they indicate position, rough shape and color) are below the level of human visual acuity and look fine. One might think of an oil painting where the artist represents pine needles on trees in a forest by a few brush strokes. At normal viewing distances our brains are quite happy to accept these artistic "marker pixels" as pine needles, but if we use a magnifying glass the illusion is shattered and we see simply brush strokes in oil paint. If we remove the magnification or move the painting further away, the illusion is again restored and we are quite happy to again see an adequate representation of "pine needles."

When we enlarge a digital file for printing, interpolation algorithms very accurately reproduce what they find. When they find true representations of detail they accurately enlarge these detail features. When they find "marker pixels" they accurately reproduce these large also and raise them to the level of human visual acuity. When we see these poorly defined details they look strange and we can't accept them as normal or accurate representations of detail.

There are always "marker pixels" whether dealing with film or with digitally acquired images. The difference is that with film we run into serious grain limitations well before these marker pixels may be seen. So we have well known limits such as 16x24 inches for normal 35mm color film. Go larger and grain destroys the aesthetic. With digital, on the other hand, the noise levels are so low that we often "try" to enlarge beyond reasonable limits. When this happens marker pixels become obvious and the effect is to destroy the "illusion" of subliminal detail.

In the example, the writer describes hundreds of thousands of leaves. Obviously, on a single tree we would never actually "see" that many leaves because even if there were that many (there aren't) we would only see perhaps 1/3 or so with a two dimensional photo. But in "theory" the writer is correct that some subjects photograph better than others with low resolution. It's often possible to make 30 or even 40 inch poster sized prints of beautiful detail from a three megapixel Canon D30 of head and shoulders portraits. How and why? Because three million pixels or sensor sampling sites are more than enough to properly define the very small amount of true detail in a head and shoulders portrait. Now change the scenario to a hyperfocal, wide angle landscape with myriad detail features and we are pushing the limits at an 8x12 print because we spread the available "resolution" much thinner. Multiply the available sampling sites by four and shoot the same scene with a twelve megapixel Nikon D2X and we easily print a beautiful 16x24 highly detailed hyperfocal wide angle landscape.

So what we must keep in mind is that with digital we have not yet learned enough to have well established limits for enlargement. We absolutely know that we can divide file matrix by desired pixel density in dpi and come up with a print size which absolutely will look stellar. What we have yet to learn is just how much we can "push" the envelope. It varies depending on the amount of detail in the frame. In general, larger frame geometry (think wide angle as opposed to telephoto) requires more resolution for enlargement purposes. Rather than waste paper, the easy way to determine is to simply make a 100% crop of a small detail section of an interpolated image and print it. If it holds detail well, so then will the entire image. With digital we simply must be "smarter" photographers to be able to squeeze the optimal performance from whichever resolution system we happen to be working with.

Best regards,

Lin
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Old 08-03-2005   #5
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Default Re: Do you agree with this statement?

Not to beat a dead horse since there are already a number of good replies, but I do agree with the statement because it applies to both film and digital. The more tiny details you have in an image, the the more resolution you need to capture them. That's the whole point of shooting medium or large format film. There is a guy who shoots black & white extreme closeup portraits for The New York Tmes magazine. I can't remember his name at the moment, but he shoots with a 4x5 film camera (at least he used to) and you can see every pore, every hair, etc. Would the same portrait look good on 35mm? Sure, but there is a qualitative difference between the 35mm and 4x5. The same will hold true for digital. Shooting a single object in the frame with limited small details will often yield a better result that shooting a forest full of trees. If you have a decent resolution digital camera, it should handle the details just fine.
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Old 08-04-2005   #6
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Default Re: Do you agree with this statement?

Quote:
Originally Posted by Lin Evans
Yes and no....* In theory it's correct that the more detail you have the more resolution you need to make larger than default prints. By default I mean that when a print density is selected in dpi (300 is commonly used for many professional print engines) they the horizontal and vertical pixel counts are divided by this desired print density (300 in this case) and you then have the "native" or uninterpolated maximum print size...

So what we must keep in mind is that with digital we have not yet learned enough to have well established limits for enlargement. We absolutely know that we can divide file matrix by desired pixel density in dpi and come up with a print size which absolutely will look stellar. What we have yet to learn is just how much we can "push" the envelope. It varies depending on the amount of detail in the frame. In general, larger frame geometry (think wide angle as opposed to telephoto) requires more resolution for enlargement purposes. Rather than waste paper, the easy way to determine is to simply make a 100% crop of a small detail section of an interpolated image and print it. If it holds detail well, so then will the entire image. With digital we simply must be "smarter" photographers to be able to squeeze the optimal performance from whichever resolution system we happen to be working with.

Best regards,

Lin
Quote:
Originally Posted by th0t
In photography there are two things that affect the resolving power of the camera system: (1) The optical resolution of the lens and (2) the resolution of the image sensor or film. It's easy to forget about the lens. Many digital image sensors in today's dSLR cameras have a higher sensor resolution than the lens. However, the lens is more forgiving and it isn't as noticeable when you exceed the optical resolution than when yoiu exceed the sensor resolution. As a result, many dSLR systems will benefit if the resolution of the image sensor is a bit higher than the optical resolution of the lens.
Lin, th0t--thank you both.* I knew I'd eventually understand this issue if someone was actually able to explain it in plain English.* This is a great place.


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