Resolution (dpi/ppi) of photographic paper

I am planning to digitize my old photo albumns for more permanent storage. The photographs (the negatives were lost
years ago) are 6x4 inch on glossy paper. I know that for printing purposes, 300 ppi is generally considered sufficient
to produce high quality images. Working in the other direction, is there any benefit in scanning the photographs at a
higher resolution?

Mike

"Mike" wrote in message

I am planning to digitize my old photo albumns for more permanent storage. The photographs (the negatives were lost
years ago) are 6x4 inch on glossy paper. I know that for printing purposes, 300 ppi is generally considered sufficient
to produce high quality images. Working in the other direction, is there any benefit in scanning the photographs at a
higher resolution?

Mike

Scan resolution and print resolution are two completely different things. Many find this confusing at first but really it is not all that difficult to grasp.

Scan resolution is the number of pixels created per inch of media being scanned. this will determine at what size you will be able to print.

So, If your image is 6X4

And you scan at 3200DPI

Your file will be 19,200 pixels wide. ( 6 X 3200 = 19,200 )

If you print this at 300 dpi, your print will be 64 inches wide (19,200/300)

Quite large.

To reproduce your original 6x4 you will need a file that is 1,800 pixels wide (300 x 6)

To achieve 1,800 pixels of a 6 inch print you need to scan at 300DPI ( 1800/6 )

If you want 12 X 8 Scan at 600dpi

If you original photograph was created with medium or large format negatives you can scan quite large and get good results. It will depend on the amount of grain and detail in you photos and your tolerance for artifacts in the image.

When you say 300 ppi, it just means 300 pixels/inch image output resolution and not image resolution. Image resolution is measured by pixels dimension. The higher the better. Apply 300 ppi to picture dimension and assumes 6 x 4" = 1800 x 1200 pixels dimension = 2.16MB pixels. If your image is RGB mode, file size = 2.16 x 3 = 6.48MB. If it is CMYK, 2.16 x 4 = 8.56MB. Same pixels dimension but different file size when apply to different color mode.

Now we come to your concept on image resolution and that is PPI. Assume 1000ppi and apply to picture dimension 1 x1.5", will be 1000 x 1500 pixels dimension = 1.5MB.

Which is better in image resolution? 300ppi and not 1000ppi. So you see it is not clear when you just say output resolution in PPI but must include the picture size to derive the pixels dimension and this is image resolution. More pixels created mean better image resolution assume all other factors at par.

Hope this will make the concept clear.

"Mike" wrote in message

I am planning to digitize my old photo albumns for more permanent storage. The photographs (the negatives were lost
years ago) are 6x4 inch on glossy paper. I know that for printing purposes, 300 ppi is generally considered sufficient
to produce high quality images. Working in the other direction, is there any benefit in scanning the photographs at a
higher resolution?

Mike

Mike wrote:

I am planning to digitize my old photo albumns for more permanent storage. The photographs (the negatives were lost
years ago) are 6x4 inch on glossy paper. I know that for printing purposes, 300 ppi is generally considered sufficient
to produce high quality images. Working in the other direction, is there any benefit in scanning the photographs at a
higher resolution?

Mike

I've been scanning old family photos in for a number of years. Mostly I use the 300 dpi in my scanning software. Very rarely I find a B&W print that will actually get more detail by scanning at 600 dpi.

There are two things that will determine what scanning dpi you will use. One is how much data is there that you can capture. Frankly most of my old family snapshots would be fully captured with 200 or 100 dpi. There isn't that much detail there. It takes a quality picture taken with a quality camera and run through a quality darkroom process to get more than 300 dpi of detail out of the scan. My family didn't do that very often.

Of course, this is easy to test. Just scan it at different dpi settings and see if you can see more detail. Once you get to a certainly point, you won't be able to see more detail. That's as high as you need to scan.

The other reason for changing scanning resolution is to change the size of the picture. I just scanned an 80 year old B&W print for my Father-in-law. There certainly wasn't much detail there. However, he wanted the picture larger than it was. So, I scanned it at 600 dpi instead of 300 dpi. I sent it to my printer at 360 ppi thereby getting a picture that was almost twice the size of the old one. It didn't add any detail, in fact it show up some flaws that the smaller size didn't.

Scan for the most detail that you need. Scan for the size that you need.

Clyde

"Clyde" wrote in message

[snip]

Scan for the most detail that you need. Scan for the size that you need.
Clyde

Don't you mean, "Scan for detail, PRINT for size??"

"JimR" wrote in message

"Clyde" wrote in message

[snip]

Scan for the most detail that you need. Scan for the size that you need.
Clyde

Don't you mean, "Scan for detail, PRINT for size??"

If you want to print large you need to scan large

DBLEXPOSURE wrote:

"JimR" wrote in message

"Clyde" wrote in message

[snip]

Scan for the most detail that you need. Scan for the size that you need.
Clyde

Don't you mean, "Scan for detail, PRINT for size??"

If you want to print large you need to scan large

Yup. Relate the dpi used in scanning to the ppi used in printing.

That 80 year old picture I scanned needed to be larger. I scanned part of it at 1200 dpi. When I printed it at 360 ppi, it was the perfect size. I scanned the whole picture at 600 dpi. Printed at 360 dpi is wasn't quite twice as big.

I ignored detail for this picture. The detail was pretty bad to begin with. Blown up with a 1200 dpi scan the detail looked worse. However, it met the goal of getting bigger.

I have scanned many pictures at the dpi that fits the detail that I can get. Sometimes the goal is size of print and other time to capture all the detail. If you are trying to both at the same time, use the larger dpi.

Clyde