Re: You're Help/Advice Please re Scanner for Slides and Negatives

If you have pixels spaced 1/4,800th of an inch apart (that's what 4800 dpi means), you can use every pixel, or every other pixel (every other pixel giving only 2,400 dpi). There are no resolution choices in between 2,400 dpi and 4,800 dpi that don't use interpolated pixels ("calculated" pixels where no actual image data exists). Below 2,400 dpi, your next choice not using interpolated pixels would be every 3rd pixel (1,600 dpi).

Bits does not have anything to do with resolution but rather color depth. The human eye can see (depending on which source you cite) somewhere between 1 million and 10 million colors. Well, 24-bit color depth is 16 million colors. More can be helpful in certain situations involving slides with really dark areas that are still discernable as not being solid black, but the benefit is marginal and usually of interest only to professionals [also note that the JPEG format is only capable of saving files in 24-bit color].

Can't help you with the glass mounts. clearly reflections from the glass are possible and may distort your results.


Peter D wrote:
Thank you for your helpful information. I decided I wouldn't use any interpolated resultions, staying with optical resolution only. From what I've read 2700 x 2700 seems to be the 'sweet spot' for 35mm. I didn't realise that I have to select an optical resolution that has to be divide into the highest optical resolution. I would have liked to go with 2700 or 3000. Are you certain I have to go with 2400 if I don't want to go as high as 4800? 2400 is fine for these slides, but I would prefer to go to 2700 or 3000, but if that would actually be worse or no better than 2400 then I don't see the point (longer scan time, larger file size).

How about the option of using 96 bit? Would that really be better than 48 bit or is overkill?

Also, any tips on scanning slides in glass mounts?

Thanks for all your help.

"Barry Watzman" <WatzmanNOSPAM@xxxxxxxxxx> wrote in message news:478991db$0$5194$4c368faf@xxxxxxxxxxxxxxxxx
4800 x 9600 implies that the resolution in one direction (vertical or horizontal) is 4800 dpi and the resolution in the other direction is 9600 dpi. Optical means that this is the "true", "actual" resolution ... you get a "real" pixel (a point actually imaged by the sensor) at those resolutions in those directions. On the contrary, "interpolated" resolution is resoulution where there are pixels between "real" pixels that are "fabricated" by interpolating between the nearest "real" pixels.

The resolution in one direction is determined by the actual sensor element (CCD, CIS element, etc.). The resolution in the other direction is determined by the stepper motor that moves the scan head across the material being scanned ... how fine it's steps are (how many points the head stops at to image).

4800 x 4800 is almost too high ... that is going to give you a scanned image (for 35mm images) of almost 32 megapixels. I'm going to go out on a limb and say that there isn't that much detail present in ANY 35mm images. 2700 dpi give 10 megapixels, which is a good value. In SOME images, a SLIGHTLY higher value might be better, but for most images, 10 megapixels (2700 dpi) is going to pretty much capture everything. The problem you have is that with a hardware resolution of 4800 x 4800, the next lower choice that you have that uses only optical resolution is going to be 2400 x 2400 (e.g. use every other pixel), and that is getting to be too low (it will give about an 8 megapixel image ... nothing to sneeze at, but more would probably be better)).



Peter D wrote:
I decided to go with the HP G4050. Mostly because of price ($180), convenience, and the ability to do 16 slides or 30 negatives at a time without any additional equipment. That's enough to make it worth loading and walking away (semi-automatic). I'll play with it once I get it, and pass on what I learn. As I go through, I'm going to single out "spectacular" slides/negs and send them away for professional scanning (89c each).

I wonder if anyone can advice me on the following:

1) Scanning slides in glass mounts - do I need to scan differently or do I treat just like the other slides?

2) Best scanning resolution and colour depth - I can go to 96 bit 4800 x4800 optical ( HP says "4800 x 9600 Hardware Scanning Resolution" - whatever that means).


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