DPI Q's

[gcha]

Some questions that hopefully some one on this board might help me with... I presently print, using an Epson 2880 to a max image size of 10X15 in, for gallery presentation, usually in B&W. I use a 4500X3000 mp file that allows me to print this size at 300dpi. Is having a camera that has a larger (24mp) file size any superior to one that has a 13.8mp imager at this printed image size? I know that there are many factors that contribute to Image IQ, but what would be the optimum for printing to a 10X15" print? Is printing at 300dpi a bench mark for best print quality. I read that 240dpi is adequate, some write that 360dpi is best, and others report that 288dpi is best with Epson printers. I am toying with the possibility of retiring my Kodak DCS Pro 14n camera that i purchased in 2003 for a more modern, higher Mp camera like the Sony a850/a900. I love the DCS 14n Camera, It has satisfied me greatly. I do not shoot at high ISO's, so it's noise problems are of no concern to me I almost always use a tripod and shoot at the base ISO of 80. I am worried that finding 2gb CF cards, Batteries, service/ parts might be difficult to find in the future. So I guess that I am looking for a reason to buy or not to buy something else!
Thanks,
Gary

[jsachs]

There is no firm dpi requirement for photo printing as this depends on the subject matter, the quality of the original image, the printer and paper characteristics, the printer driver, viewing distance, and how the image is sharpened before printing. In general, the contrastier the image the higher the resolution you need to render it optimally. In an extreme case like black text on a white background, 600 to 2400 dpi is the usual range of resuloutions. For a very soft image, 100 dpi may be more than you need. Somewhere in the range of 200 to 300 dpi usually produces good to excellent quality prints from normal subjects.

All other things being equal, more pixels is better, but things are seldom equal. The size of the image sensor is also important as is the quality of your lens and how solid your tripod is. Smaller pixels usually means more noise and less sensitivity so there is a point of diminishing returns in how many pixels you place on a sensor of a given size.

[gcha]

J.S.
Thanks for the reply. That is what I have always thought. The only reason to re-think those relationships, is because of new camera technology sales hype, etc., and the fact that my DCS Pro 14n is getting, like me, a little long in the tooth. Being retired and no longer working as a pro, these equipment upgrades are frightening! When I purchased the DCS14n new, it was $3900.00, body only, now just seven years later, it maybe has a value of $600.00!!! OUCH This is not like the old film days...
Thanks again,
Gary

gcha.zenfolio.com

[keithrj]

I have read many times that you should try and print at the native resolution of the printer. Additionally, if you can't or don't want to print at the native resolution then print at some multiple or simple fraction of that resolution. Many Epson inkjet printers have a native resolution of 360dpi. The printer driver and/or the software will do some interpolation to produce the required output size based on image size and required dpi. It is for this reason that you should select an appropriate dpi to minimise the amount of interpolation done.

As an example, for a 360dpi printer you could print at 720 (360 x 2), 360 or 180 (360 / 2) depending on the quality of the output you are looking for.

As far as cameras go, I only upgrade when there is a real need, like increased responsiveness of newer cameras. If your camera does what you need and you are not missing shots because of the camera then don't look for a replacement. Digital cameras are like computers, they WILL NOT hold their value so don't buy something expecting to get your money back. Also, prices keep falling so no hurry to upgrade, just go out and get a few more CF cards and batteries to tide you over until you do decide to replace your trusty camera.

[HanSch]

Because of my job I have access to many printers (Epson, Canon, HP and more), wide format and "normal" format. Keithrj's remark that you should print at the native resolution of the printer is correct. For Epson this is 180/360 dpi, for HP/Canon 300/600 dpi. In most cases, however, you will hardly see the difference if you print a 300 ppi file on an Epson printer.
As Jonathan stated, a 200-300 ppi file is sufficient for high quality printing (the printer should have a higher resolution of course, because headspace is needed for halftoning). I tried to see the difference between 360 and 720 ppi (without interpolation) on an Epson printer, but the differences are really minor. On the other hand, I printed D-sizes from good 10 MP images, properly enlarged and sharpened, and from normal viewing distance the prints are completely satisfying. The prints would probably be better if the image originated from one of the latest full-size many MP sensor cameras, but only on closer look. For large prints you always have to squeeze as much as you can from your camera (lenses, tripod), but as a former pro that's nothing new for you ;-)
Text printing is different, because no halftoning is involved. 600 dpi is good, 1200 dpi excellent and I doubt if anything can be gained beyond.
Printing on traditional (wet chemical) photo paper is also different, because this is a contone process. Unless your image contains very small detail, 150-200 ppi will be sufficient.

[Dieter Mayr]

Gary, as long as you are satisfied with the result your equipment gives to you, i would not see any reason to change it, if there may be a MP-hype or not.
The new cameras have so high resolutions, that often the lens (especially cheap zooms) are the limiting quality factor, not the sensor.
So, if your camera works like it should and you are satisfied with the (technical) image quality, i would not see a reason for updating.