What does "scan image, 20cm at 300dpi mean"???

[jrong]

Alright, any desktop publishing gurus here? 🙂

I'm fairly stumped when it comes to scanning at a certain dpi or whatever. I just tend to scan what I like.

I have a requirement - to scan a 35mm slide, "it must be 20cm high at 300dpi".

What does this mean, and how do I do it with my Vuescan software? Sorry if this sounds dumb, but I really have no idea. I usually scan all my 35mm slides at 1200dpi and then resize it in Photoshop to about 700 pixels across!

Someone slap me... :bang:

Jin

 

[ffttklackdedeng]

Hi Jin,

20cm high at 300 dpi = 8 inch high at 300 pixels per inch = 2400 pixels high. If high means on the short side of the picture, you should scan at approx 2400dpi. If it means the long side of the picture, approximately 1600 dpi should be enough

Cheers,

 

[jrong]

Ah, that makes sense. I wish they'd just say "Scan at 2400dpi". 😉
Thanks!!!

Jin

 

[drewbarb]

They want to make a print. The requirement to scan at 20cm at 300dpi refers to print measurement (presumably of the longest dimension) and file final resolution respectively. Your method of scanning at 1200 and resizing to 700 pixels is fine for screen viewing, but you will need to scan at somewhat higher resolution to make a photo quality print. The 300dpi they ask for is important to remember, since 300 dpi is the industry standard for photo quality prints. A file which will produce a 20cm print at 300 dpi will be 2362 pixels across.

Scan at the highest resolution you can, do your file adjustments till you like the way it looks at full resolution, then go into image size, set dpi to 300, and see what the size will be. With Photoshop, you can look at it in pixels and in measurements like inches or centimeters. Good luck.

 

[oscroft]

I wish they'd just say "Scan at 2400dpi"

They usually can't, really - it depends on the format of the original and on the amount of cropping you're going to do for the final image (the more you crop, the higher the scan dpi you'll need).

So rather than trying to work out what every individual's scan resolution needs to be (taking into account those variables), it makes much more sense to just specify the required resolution of the result and leave it to you.

 

[alcaraban]

Ah, that makes sense. I wish they'd just say "Scan at 2400dpi".

They can't, as if you shot in 6x6 that wouldn't be true. Actually, they could just say "2400 dots, long side". But the real fun is how they mix cm and inches.