scanning negs versus prints

[john_dixon5]

Can someone help me in my calculations.

 

1) If I scan a 2-1/4 x 2-1/4 negative at 3200 dpi, I get about 16,000

dots total. (Am I right so far?)

2) If I then blow it up to 20" x 30" I get 27 dpi, which is useless.

(16,000 divided by 600 (20" x 30")

 

Comparing to scanning in a 8" x 10" photographic print.

1) Scan 8" x 10" print at 3200 dpi, I would get 256,000 dots.

2) If I blow up that scan to 20" x 30" I would end up with 426 dpi,

which should give a good print.

 

I know that photo prints (glossy) have a resolution, but surely they

have to be better than negative scanning, which appears to be of no

value if you intend to blow up to large size.

 

Or am I miscalculation something here?

 

Thanks

 

John

[NetR]

>Or am I miscalculation something here?

 

You got it.

 

Instead of what you did, which is 3200 x 2.25 x 2.25 = 16,000 approx, why not try:

 

(3200 dots per inch x 2.25 inches along one side) x (3200 dpi x 2.25 along the other side).

 

This gives you about 52 Megapixels. (A bit less actually as a 2 1/4 sq neg is more like 2 1/6 inches across).

 

Regards, Ross

[yeow_teng_kuah]

Before we start, you will have to understand negative consisted of billions and billions of silver halide ... micro dots that existed to react with lights. Thus for your answer below :

 

1) wrong ..... 2.25in * 2.25in is (2.25*3200) * (2.25*3200)= 7200 * 7200 = 51840000 .... if you blow up to 20" * 30" = (7200/20) * (7200/30) = 360 * 240 (DPI) .....

 

Depending on how you see it .... you can see it as 240 DPI for a 20" * 30" print or a 360 DPI .... but most people just add 360 and 240 together and divided it by 2 to make it 300 DPI ;P..... (Just plain lazy to explain). But anyway for calculation, based on a X * Y on 300 DPI .... the picture can be blown up to (7200/300) * (7200/300) or a 24" x 24" picture without losing much resolution. For a 20" x 30" picture, you will be printing it at 240 DPI. Slight lost of quality, noticeably you are actually printing it to 30" * 30" than cut it to size as your film is a square film.

 

Anyway, a 8" x 10" photographic print is already a 8" x 10" at 300 DPI .... thus even if you scan it at 3200 dpi, the maxmum resolution is still 300 DPI, you will only get interpolated version, which just makes the "dots" bigger.

 

The end result of a photo print will be a lot more hazy then if you scan it from negative from a dedicated film scanner.

 

Just think of it as this way. The CCD on a flim scanner is trying to scan nearly 160 billions of micro dots, thus it combine what it "sees" into one big dot (something like trying to resize a picture with a lot of dots to a smaller one with lesser dot in photoshop). Thus in theory, if there exist a film scanner scan every micro dots, of a 2.25in film, it would have to be a 177778 dpi scanner.

 

The CCD on a normal scanner, on the other hand works the opposite when you are trying to scan 8.1 million dots (8 * 300) * (10 * 300) to be 54 million dots (20 * 300) * (30 * 300) (something like enlarging a picture six times it's size)thus for one dot, the software will be creating 5 more dots around it making it looks bigger. But the details are not there, thus it becomes pretty hazy.

[kelly_flanigan1]

If you are using an "epson like 3200 flatbed"; you are getting at 3200 pixel/inch image of that 2x2 inch square negative; that has about the same info as a film scanner at maybe 1600 to 2000 pixels per inch. The flatbed is ALOT less sharp than a dedicated film scanner; at the same dpi/ppi setting. Thus the math is abit optimistic here.<BR><BR> A 2x2" negative would be enlarged by 15X; to give a 20x30" negative. Thus your 3200 dpi/ppi scan; could be printed at 3200/15= 213 pixels/inch; on our printer. If I resized it to about 135 pixels/inch for 20x30"; as an experiment; it would appear just as sharp; if "only" a flatbed scanner was used; because a flatbed doesnt pull out the detail; like a film scanner does.,

[yeow_teng_kuah]

I have to agree with Kelly there ..... my mistake for note asking what type of scanner are you talking about and just assumed you have a dedicated film scanner. A Flatbed scanner will not provide details above half it's advertised DPI due to light leakage and the inability to capture detail, shadow and sharpness..... (Ever wondered why film scanner is so much more expensive?).

[john_dixon5]

Thanks everyone for some great techical answers.

 

I know the Epson 3170 flatbed scanner is not as good as a film or drum scanner, is it worth considering at all, or am I better off giving the negs to a scanning service lab for scanning?

 

Thanks very much.

 

John

[david_henderson]

This probably agrees with the others. Firstly it's generally the

case that you're better off scanning the most detailed version of

an image you have. Its difficult to see how a print can have all

the detail of a negative. There might be exceptions if the print

you have is very interpretative and your photoshop skills aren't

great- for example a heavily manipulated b&w fibre print.

 

Second I would not be looking to make a 30" x 20" print at 15x

enlargement from a flatbed scan unless I had no alternative.

You'll get a better (sharper more detailed) print from a scan by a

good film scanner.

[lachaine]

It depends what your purpose is in scanning. Obviously, if you already have made a darkroom print and it looks the way you want it to look, then almost any flatbed scanner will scan an excellent representation of that print (since it's so big compared to a negative, you don't even need much beyond 150-300dpi). But you can't really enlarge it any further, beyond its size when you scanned it. Mind you, it will be huge on the computer screen, but if you try to print it larger than the original print you scanned, you're going to lose some significant quality - because all you're doing is spreading out the "pixels" more.

 

If, on the other hand, your purpose in scanning is to go the digital darkroom route once you have the negative and you're not interested in making a conventional print, then, it's far better to scan the negative. The reason that in this case you want to scan the negative is simply because a negative contains a lot more information than usually makes it onto the print (ie. film has a wider latitude than the photo paper does - you don't have to dodge and burn a negative, but you do need to dodge and burn in the darkroom to get all the information you want from the negative onto the paper). Therefore, there's more for you to work with in the digital darkroom when you scan the negative.

 

If you want to blow up a negative to a very large size, you're probably better off just having the print you want made the conventional way from the negative. From what I can tell where I live, commercial scanning of medium format gets pretty expensive (so are big enlargements, but it's not like you make a big enlargement of every photo you take).

[www.ianleake.com]

Hi John,

 

I use a 3170 and it's fine for web work and small prints (e.g. up to 10x8). I've had a small number of larger prints (e.g. 20x16) made based on its scans, but I had to do a lot of work to get them how I wanted. The biggest problem is not so much the DPI, but its inability to record deep shadow tones accurately.

 

If your prints are destined for a gallery or a paying customer (or if you just like lots of really good big prints), then I would invest in a better scanner.

 

After all, you get what you pay for ;-)

 

Best regards,

 

Ian.

[richard_milner2]

I started by flatbed scanning prints but the quality on that was fairly poor, and it was time consuming.

 

I then looked at a dedicated film scanner. The MF models are priced at about ?2,000 in the UK, which is a lot of money. Also you need a good computer and it takes time, etc.

 

So now I have scans made of selected frames once I've seen my proof prints. By saving them up in batches for a bulk discount, the cost is under ?1.50 per image. The resulting file is a 25MB JPEG, which is more than enough for email or web purposes, and can be printed to normal size. It's claimed they are good for printing up to 12 x 8 but I haven't tried that.

 

I only manage to produce one or two images per week which are worth scanning, so it will take me over 10 years to spend as much money this way as if I had bought the film scanner.

 

When I want big enlargements, I have them done the old-fashioned way, from the negative. Optical prints (in fact they're often done digitally these days) are about as cheap and quick as digital prints anyway. In fact, the major expense in prsenting my images turns out to be custom mounting and framing.

[john_dixon5]

Thank you everyone for terrific advise and in depth technical information.

From what I hear its not worth getting a flatbed, so today I took a 120 (6 x 4.5) negative to a specialist place to high res scan it in.

For ?5 each they said they could scan it in at 32megapixel @ 10" x 15", which they said should still be good when blown up to 20" x 30".

They also said they could use some other equipment for even higher res, but was quit expensive (I did not ask how much) So I am trying the ?5 scan, and will compare it to the 8" x 10" that I scanned in on my flatbed (cheap Epson 1260) and blow up to 20" x 30"

 

Thanks again everyone

 

John

[richard_p]

For scanning MF film, try imagerylab.com. They have good prices for MF scanning. They do pretty jobs. But you need a big computer (1 GB ram) to handle the files (compressed TIF 200-300 MB for each 6x6).

 

Richard

[john_dixon5]

Richard,

 

I am in the UK, that site you mentioned is in the USA. But I have found a place here in Derby to do 4000dpi scans for ?5 each

 

Thanks

 

John