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Please explain a high resolution picture

Ann Coba , Dec 06, 2008; 07:38 a.m.

I have a Nikon D40X and sometimes I shoot in raw. Will the raw pictures be considered a high resolution just because it's a larger file than the JPEG?
I have been reading the wedding forum and I see that is a common practice to give sometimes to customers low end resolution pictures on a CD.  If you took high resolution pictures in the first place how you convert to a low end? Just by scaling down the size?
I have been doing a lot of reading about photography but for some reason I have not found a very clear definition and I'm still confused.  Please help me understand!!!
Thanks

Responses

Stephen Lewis , Dec 06, 2008; 08:09 a.m.

There's actually several questions here. Generally resolution is the ability to differentiate two objects (such as lines) and is usually a function of both sharpness and contrast. Shooting in RAW merely captures the full range of data which your sensor and electronics can capture, allowing for significant post processing, if necessary, and conversion to a lossless format (such as TIFF). JPEG is a compressed format which losses data each time it is opened and saved. Lo resolution output from high resolution capture essentially makes the pictures ok to look at, but unusable in terms of enlargement. It is accomplished in any of the popular post processing programs such as Photoshop, Nikon Capture, etc. generally resizing the pixel output and using the "save as" options. Hope this helps.

Ellis Vener , Dec 06, 2008; 08:34 a.m.

"Will the raw pictures be considered a high resolution just because it's a larger file than the JPEG?"

Resolution is affected by 4 things:

  1.  number of pixels
  2.  accuracy of focus.
  3.  optical quality of the lens
  4.  quality of sharpening technique.

     

In camera produced JPEGs are essentially raw data that has been rendered into a compressed RGB format where pisels with similar values to neighboring pixels are averaged together so yes you can lose some detail there, depending on the level of compression. But they also have sharpening already applied as well as being rendered into 8 bit per channel form .it is sort of like a Polaroid  where the photo comes out of the camera already developed ( this is a bit of a stetch: in the case of a Polaroid the developing starts as the negative /print material comes out of the camera with the developing chemicals  spread between the two sheets. but it is still a good analogy for JPEGs.)

Shooting raw is like shooting color negatives with an exceptionally large dynamic range. All of the information recorded by the sensor is there , usually complete with a very minor amount of sharpening by the in camera processing firmware but Nikon does this less than Canon. You potentially have more information and can control the sharpening process  and the form of output in the processing stage (raw conversion software: Adobe Camera Raw, Nikon Capture NX2, etc.) and in the post-processing stage (Photoshop).

Don E , Dec 06, 2008; 10:19 a.m.

"I have been reading the wedding forum and I see that is a common practice to give sometimes to customers low end resolution pictures on a CD. If you took high resolution pictures in the first place how you convert to a low end? Just by scaling down the size?"

Probably what they mean, and yes.

"I have not found a very clear definition and I'm still confused."

Imagine shooting down any street with a lower quality lens and sensing medium, and then doing so with better kit. A street sign 4 blocks away in the first instance, when enlarged may show a blocky greyish/whitish area. That's low resolution. The second might show the letters clearly and be legible. That's a higher resoltuion.

James Dainis , Dec 06, 2008; 11:14 a.m.

I think a problem arises from the fact that "resolution" with digital means two things.  With film "resolution" meant lp/mm (line pairs per millimeter) that could be resolved or separated. That would be an indication of sharpness and clarity. With digital "resolution" also means image size as in an 8 MP camera has twice the resolution of a 4 MP camera.

 


While the resolution (image size)of the camera on the right is twice that of the camera on the left, the resolution (sharpness) of the camera on the left is much better than the resolution (sharpness) of the camera on the right.

 

Tommy Lee , Dec 06, 2008; 11:22 a.m.

Will the raw pictures be considered a high resolution just because it's a larger file than the JPEG?

RAW normally doesn't associate with definition of resolutions. Typically, a RAW file output from a DSLR is the format that contains the most accurate description of the given image. So in that sense, it is high resolution. Some camera however can produce a lower resolution RAW file (ie sRAW). So there are exceptions. JPEG also can produce the same amount of pixel as a RAW file could. So it is not low resolution by definition.

Weddding and other event photog typically give out low resoutions image for computer viewing but not high enough to get high quality print for keep. The idea is one buy from the photographer for the prints. One can view a 800 by 533 image in the computer well but at that resolution, a 4 by 6 print will not look well. You can use photoshop (element or CS) to batch reduce to this resolution.

Definition of " High" in resolution changes with time. Just not too long ago, 4 Megapixel was consider high.

James Dainis , Dec 06, 2008; 11:38 a.m.

In the informative post that Tommy gives above, he is using "resolution" to mean image size. To substitute "image size' for 'resolution" clarifies things a bit.

Weddding and other event photog typically give small image sizes for computer viewing but not large enough to get high quality print for keep. The idea is one buy from the photographer for the prints. One can view an 800 by 533 image in the computer well but at that image size, a 4 by 6 print will not look well. You can use photoshop (element or CS) to batch reduce to this image size.

James Dainis , Dec 06, 2008; 03:58 p.m.

The Nikon D40X has a maximimum resolution (image size) of 3872 x 2592 or 10MP.

Printed at 300 ppi that would give a photo of 12.9 x 8.6 inches.

3872/300 = 12.9
2592/300 = 8.6

Reduce the resolution (image size) to 800 x 535 in image editing. That will show nicely on a 1200 wide monitor but, if people try to copy and print that image at 300 ppi, all they will get is a 2.7 x 1.75 photo.

800/300 = 2.7
535/300 = 1.75

Ann Coba , Dec 07, 2008; 10:14 a.m.

Thanks to all of you for your input. I understand it much better now.  I always thought that the amount of pixels was the only factor determining resolution.  :)

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