That, to some extent, is an urban myth
Qimage was originally developed to make A3 prints from a 2M px camera and since then it's been improved considerably.
You can get a good print with 100 ppi, 300/360 is better and should be more than adequate.
A 35mm slide scanned at 2400ppi will give about 330 ppi on a 10" print; and the same for a 5" print where the negative was scanned at 1200 ppi.
Why don't you compare test prints from a slide scanned at both 1200 & 2400 ppi and try a 10" print from each. You may be pleasantly surprised. Tell us how you get on.
Terry.

Try it. If you don't want to use a full sheet, print "test strips".
Terry.

Ok,

I took three scans of a 35mm Kodachrome slide, winter scene, snow and leafless maple trees...lots of bare branchs on the trees for a good resolution test.

Scans were at 2400, 4800 and 6400 DPI on the Epson V500 scanner with the included Epson Software.
I used medium USM, medium grain reduction, color correction and HIGH dust removal.

I then took 3" test strips from each and printed them out on a single sheet of 13 x 19 PGPP (Epson Glosst Prof) paper. So the 35mm slide was enlarged via Qimage to a 19" length.

I can see little or no difference in either of the scanned prints!!!

Now my wife consitently picks out the LOWEST 2400 DPI scan as the best resolution based on shadows on the snowy areas of the print!!!

So  I guess if I print out at 2400 dpi I should have no issue making a 13 x 19 print that is virtually identical to one printed from a 6400 DPI scan using Qimage!


I was thinking that taking such a small 35 mm slide scanning and printing to a large print is a real tough test of the technology employed to be able to get a decent print etc...

I was wondering again if the negative or source area increased what would happen to this relationship>

Would the results scale if the negative was a larger format? I would think so.

If anyone has any experience in this area please share this knowledge!!

All the best

Alex

 

Hi Alex,

Looking at it from another direction -

Doing some rough comparisons, considering the narrow width/height of the slide (about one inch). You want to print at say 720dpi on 13inch wide paper, using Qimage. Now, in practice, printing with Qimage to larger prints, bearing in mind usual viewing distances, etc., you can start off with with a much lower resolution than 720ppi. Fwiw, the height of a canon 40d camera image is about 2600 pixels, and I can get good prints larger than your final size with those images and Qimage. Now, allowing for a the sensor size, if the 40d was a full 35mm frame, at same pixel density, then it would equate to 3900 pixels - The 5d, which is full frame, is about 3000 pixels, and that pushes the lenses to their limits, according to some (but it is not just ppi/dpi that matters).

So, bearing in mind the above, and the likely quality of the slides, I would think that 2400ppi scanning would be quite satisfactory, as you have found. I believe the native optical resolution of your scanner is 6400ppi, so possibly a scan at 3200 or some other factor of 6400 may be faster or give a better result than 2400, I think I would try 1600, if it speeds up the process. You can't beat testing things out for yourself  If it is really important, then as Terry says, don't clean up the image in the scanning software, and I would scan at 6400ppi.

(I think you may have made a few typo's in your description, or maybe it's my misunderstanding, but you don't want to/can't print out at 2400 dpi using
Qimage)

The rule of thumb used to be, 30/40 years ago, if you wanted to print at same size as the original, you scanned at 1.5 times the the ppi of the final print resolution, but that was before ink jet printers were around, iirc. (Somewhere, I've still got my early canon scanner - monochrome only, which I converted to colour - using three filters on sliders, scanned three times and combined in some software written by Computer Associates - who now, like many, seem to be a shadow of their former self...)

Best wishes,

Ray

Thanks for reporting back, you are going to be very busy 
Terry