What size 'photo' quality?

[davewatson]

I am new to digital photography - I have a G1 camera and an HP 1220c printer.
I would like to know what is the largest size of print that I can make from the full image size, whilst achieving near conventional photo quality, at each of the camera's resolution settings of
Large (2048 x 1536), Medium (1024 x 768) and Small (640 x 480).
How do I establish similar limits of print size for partial images?
Thanks.

[polarinda]

11X8 inch 180dpi

[Mike K]

Polarindas response was for native resolution, or the number of pixels that the camera generates. Of course you can make the picture larger than that by interpolating pixels, a process called upsampling. The loss is quality is not too severe, depending upon the desired size, initial image quality, the distance it is viewed from, etc. The density of the pixels can also be varied, which may change the perceived print quality. In other words, one could double the 180 ppi to 360, but the picture would be half the size unless one upsampled to create more pixels. These issues are covered in summary form in this tutorial:
http://www.luminous-landscape.com/understanding_resolution.htm

Regards, Mike K

[polarinda]

Just a question to mike. When u double to 360dpi at 11X8 by unsampling, wouldn't u get a blurred image? As u said, it depends on a lot of factors, but i remembered reading somewhere that using Genuine Fractals to unsample is a better way to go about not getting a blurred image.

Anyway, 180dpi at 11X8 is about as good as what u get on the screen from Raw.Almost "what u see is what u print"

[davewatson]

Thanks for your response.
Dave

[Mike K]

Whatever your choice of print density (180-360 ppi being the target range), the interpolation of pixel data (upsampling) becomes more critical at greater factors. At modest upsamplings (say 9 mb TIFF to 14mb TIFF files, 1.5X) the normal photoshop bicubic spline should do a good job. Genuine Fractals has an algorithm that tries to maintain "edges" that it identifies, to keep from rounding them off during the interpolation process. Most agree that its effect is most noticable at large upsamplings, 4-5X and above. A few feel that these "edges" seem unnatural to them. Another popular algorithm is packaged within the Qimage printing program and is called Lanczos print interpolation. In all cases, sharpening is then applied after upsampling so as to not round off the "sharpened" image. There have been several threads in dpreview forums showing examples and arguing the merits of the various upsampling techniqes. The luminous-landscape tutorial mentioned previously is pretty good at describing the basics of this topic.
Regards, Mike K