How much of a difference ?

[John_Olexa]

I'm getting some old 35mm slides turned into CDs. Here are my choises " If you are looking for a pretty good scan choose the Pro SD (scans at 3000 DPI). If you are looking for the best scanning service choose the Pro HD (scans at 4000 DPI). "

Can anyone tell me how big a difference is 3000DPI & 4000DPI ?? I want them to look the best of course but is there THAT big a difference? There is in the price.

appreciate any help.

 

[480sparky]

I'd say it depends on the resolution of your original slides. If you shot, say, ASA 200 or 400 slide film, 3000 or 4000 would suffice. I had to go to 9200dpi to see the grain in my old K-25.

 

[John_Olexa]

Thanks, these were all ISO 100 . I should have added for what it's worth, I plan on trying to have them published. Some were! but nowadays most publishers want digital. All of them are lightning images.

 

[Josh66]

In my experience, it's not a huge difference. I usually scan at 3600, sometimes 4800 (sometimes more than that). The image quality is about the same either way... IMO, it mainly depends on how large you want to print...

3600ppi in 35mm gives you images roughly 4500x3000 pixels.

 

[John_Olexa]

Thanks! This company gives you 3 choises 2000, 3000 or 4000 DPI.

 

[robbins.photo]

I'm getting some old 35mm slides turned into CDs. Here are my choises " If you are looking for a pretty good scan choose the Pro SD (scans at 3000 DPI). If you are looking for the best scanning service choose the Pro HD (scans at 4000 DPI). "

Can anyone tell me how big a difference is 3000DPI & 4000DPI ?? I want them to look the best of course but is there THAT big a difference? There is in the price.

appreciate any help.

Ok, going to go out on a limb here and say.. 1000 DPI?

Lol - seriously though the biggest difference will be in the size of the final image, allowing you to print larger from the higher DPI scans. In actual practice you won't really see a huge, huge difference between 3000 DPI and 4000 DPI other than that.

 

[Josh66]

I would probably go with 4000, "just in case". My scanner has different increments between settings, but 4000 should give you a pretty decent image size.

My 4800ppi scans are around 6700x4400 pixels - plus or minus depending on how close I cropped to the edge of the frame.

4000ppi will probably come in somewhere around 5500 pixels on the long side. (That's just a guess based on my results for 3600 and 4800 ppi.)

 

[bratkinson]

At 6700x4400 pixels, that's the equivalent of a 29.48MP camera RAW image! That seems like overkill to me and consumes incredibly large volume of whatever storage media you choose...and backup to. For the handful of 35mm slides I've digitized, I've been more than satisfied with 400-600 PPI.

And for what it's worth, one of the biggest problems I've encountered with my own digitizing efforts as well as others who have done it themselves or sent them somewhere to be scanned...is not removing the dust from the slides before scanning them! The plastic mount slides I have are the absolute worst when it comes to having dust on the slides! Yes, the filters in Photoshop can do an admirable job of removing dust and scratches, but getting off the dust up front gives better results!

 

[Designer]

I plan on trying to have them published.

Also might depend on the publishing technology. If the publisher can't resolve any better than 3000DPI, then why pay for the higher resolution?

 

[Josh66]

At 6700x4400 pixels, that's the equivalent of a 29.48MP camera RAW image!

And I can go higher than that too. LOL! My medium format scans are usually around 10,000 pixels, on the short side (I mostly shoot 6x6, so that would be both sides for that format).

I really don't worry about backups too much, since I can always just rescan the film.

...is not removing the dust from the slides before scanning them! The plastic mount slides I have are the absolute worst when it comes to having dust on the slides! Yes, the filters in Photoshop can do an admirable job of removing dust and scratches, but getting off the dust up front gives better results!

It's almost impossible to get it all off. There always seems to be dust, lol. I hate it. Maybe 90% of my editing time per frame is cloning dust out... Sometimes I don't even bother cloning it out though - it gets tedious real fast.

I keep the film in sleeves, and it is only exposed to the air while it's drying, and while I'm moving it from the sleeve to the film holder to be scanned, but dust still gets on it. I even blow it off with a rocket blower (both sides) before scanning, and that doesn't get it all either. I have one of those sensor cleaning brushes (the kind you statically charge on a sheet of paper) - I might see if that works better than the blower...

I plan on trying to have them published.

Also might depend on the publishing technology. If the publisher can't resolve any better than 3000DPI, then why pay for the higher resolution?

More room to crop, higher quality file to work on before exporting for the intended use, might want to print them for something else one day, etc... I can think of a bunch of reasons I'd rather have the larger file.

 

[amolitor]

I would probably go 4000 DPI, myself. That's less than 80 line pairs/mm, which is about what good slide film will resolve in the first place if you're quite careful and have good equipment.

There are at least two approaches to this, though. One aims simply to make a digital copy of the picture, whatever it is in the slide that is pictured. 4000dpi is probably OK for that. The other aims to truly copy the film, to make a copy not merely of the picture but of the film itself, with all its dye blobs and grain and so on. This takes.. a lot more pixels.

Even to recover the just the picture, it's not simply a case of "well, film only captures X so as long as you're over X, then you lose nothing". That's just not true.

When you shoot a piece of film, there is some loss. The film can only resolve so much, it can only handle color in such and such a limited way, and so on. When you scan it, there is further degradation, always. The scanner loses some more resolution for you. The color limitations of the scanner add on to the color limitations of the film, so you lose more color fidelity.

This:

Real world -> film -> scanned image

is a system, and both stages are losing stuff. If the second stage is crazy high fidelity, then you'll lose very very little beyond what the film stage has already lost you. If the second stage is good, maybe about as good as the film, then you're undergoing similar degrees of loss of fidelity twice.

Now, for print, it probably doesn't matter that much. There's so much loss putting the picture onto a magazine page, it hardly matters. For web publication, any old crap will do, really.