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Scanning Help

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What's the best dpi to scan at? For photos and posters. Thanks Read More
superfreddy Avatar
8m, 3w agoPosted 8 months, 3 weeks ago
What's the best dpi to scan at? For photos and posters. Thanks
superfreddy Avatar
8m, 3w agoPosted 8 months, 3 weeks ago
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Responses/page:
#1
Assuming file storage space isn't an issue then the optical resolution of your scanner.
#2
EndlessWaves
Assuming file storage space isn't an issue then the optical resolution of your scanner.

Not sure what that is lol I have an all in one printer, so it's a HP ENVY 4507
#3
At some point, increasing the scanning dpi will not improve things because you will have reached the resolution limit of the source photo/poster.
What DPI are you printing at?. If you scan too big you may end up loosing quality due to the software resampling/resizing the image.

HP ENVY 4507
Resolution: up to 1200 x 2400 pixels per inch (ppi) optical; 19200 ppi enhanced (software)

Edited By: dai007uk on Oct 26, 2016 19:34
#4
dai007uk
At some point, increasing the scanning dpi will not improve things because you will have reached the resolution limit of the source photo/poster.
What DPI are you printing at?. If you scan too big you may end up loosing quality due to the software resampling/resizing the image.
HP ENVY 4507
Resolution: up to 1200 x 2400 pixels per inch (ppi) optical; 19200 ppi enhanced (software)

So bearing that in mind, what would be the best dpi to scan at?
#5
About 300dpi
http://www.rideau-info.com/photos/printshop.html

To be honest you're better off getting negatives scanned as they are a lot higher quality than photos.
#6
kester76
About 300dpihttp://www.rideau-info.com/photos/printshop.html
To be honest you're better off getting negatives scanned as they are a lot higher quality than photos.

Well this will be my little boys artwork from school and digital photos.
#7
superfreddy
kester76
About 300dpihttp://www.rideau-info.com/photos/printshop.html
To be honest you're better off getting negatives scanned as they are a lot higher quality than photos.
Well this will be my little boys artwork from school and digital photos.
Depends on how much you want to blow the images up by. The higher the dpi/ppi the more detail and the larger you can stretch the image to. I assume standard dpi of school picture is around 300dpi.
#8
For the artwork use 1200dpi (the lower of the optical scanning values) anything above this will just be data that is useless and only inflate the scanned image size.
#9
As above but if you want full control you'll want to use a camera to take raw images. From there you can produce whatever you like.
#10
if its anything like the ones i have seen then you are only going to be offered a couple of settings anyway no matter what theoretical dpi the scanner claims
300dpi is often the standard upper resolution and will give you whopping files so see how it goes and maybe even go lower

Edited By: brilly on Oct 26, 2016 21:13
#11
300 dpi is giving me a file of 672kb so it seems too small to be high quality?

Isn't there some sort of rule of thumb, like the best dpi to scan everything at in case you want to blow it up to a bigger size?
#12
superfreddy
300 dpi is giving me a file of 672kb so it seems too small to be high quality?
Isn't there some sort of rule of thumb, like the best dpi to scan everything at in case you want to blow it up to a bigger size?
as in first post, high as possible basically
seems i remembered wrong, 600dpi was standard high level but i have a 1200dpi scan of a passport photo - ends up at 4MP and 1.2MB (oddly have a 20MP passport photo at 50MB which is why said files would be massive i think!)
an A4 @ 600dpi ends up 35MP and 5MB-15MB


Edited By: brilly on Oct 26, 2016 21:35: .
#13
600 dpi
#14
Thank you. Highest I can do is 2400dpi
#15
Jpeg is a lossy format. Cameras tend not to have the same processing power of pcs so they dont compress as much. Raw is massive but scanning as a jpeg will shrink it to nothing. A good paint package will reduce the bit depth if there isn't a high number of discreet colour on a colour count.
#16
Thanks all, no consistent answers though so I'm swaying on scanning everything at 1200dpi?
#17
Depends how big you want to stretch it. Remember most ipads retina screens are below 300ppi which is pretty much 300dpi.
#18
superfreddy
Thanks all, no consistent answers though so I'm swaying on scanning everything at 1200dpi?

Yeah, you always want the originals as high quality as possible so scan at your scanner's resolution (1200dpi) and save it as a losslessly compressed format (raw, tiff, tga, png) and not a lossy format like jpg.

File size will depend on the physical size of the object (physical size x dpi = total number of pixels) as well as the content of the image. Large blocks of the same colour compress more than lots of detail) so it doesn't mean much alone.
#19
You're being told all manner of answers here, and in my opinion many are wrong.
It really depends on what it is that you're scanning, so let's go with an example of scanning a printed photo.
It will almost certainly be printed at 300dpi. That is a fixed value and cannot be changed, no matter what resolution you scan at. If you scan this photo at 300dpi you can have a digital image of the same resolution and quality as the photo itself, although yes use a non-lossy format like tiff (jpeg will compress some colours). You can then print it out at the same size and achieve the same quality as the original (working on the presumption of having the same quality printer...). Scanning this photo at a higher resolution is pointless as there is no extra detail there, it is printed at 300dpi and that is all there is available. Scanning at a higher dpi will not mean that you could print larger versions of the original as the detail is not there. Think of the photo as being a piece of cut fabric, the size is set, you could make it bigger by stretching it but the fabric will distort and stretch. However, it is important to remember that the distance at which a larger print is viewed is further away than that which you view a smaller print, so you may consider the quality acceptable. Either way in this case you can only work with what is available and that is the print resolution; scanning any higher than that will just inflate your file size and contain no extra detail as there is simply no more actually available.

For things that aren't printed options are a little different. Your scanner has a resolution of 1200x2400, meaning that the optical resolution is 1200. Note that this is a theoretical number and most won't actually get close to it, it's more engineering and marketing than an actual value. I for example scan 35mm film and slides and have a dedicated film scanned with a theoretical resolution of 10000dpi, however optically it hits 5000dpi. A drawing using any medium isn't made up of dots of course so you could scan it at whatever size you like, but no more than the optical resolution as you would just be inflating the file size with no benefit. You could scan a drawing at 1200dpi and enlarge it and hence make it much bigger without loss of quality, although you will be restrained by print quality. In this case however I'd save it as a jpeg as you're unlikely to want to store the value of every single pixel/dot.

So, in sum, for already printed items scan at 300dpi as that is a set value based on the print resolution. For non-printed items you might as well scan at a larger dpi but use jpeg formatting and save yourself some space whilst retaining a larger image (in 'physical' pixel terms, if not in file size).

It's a complex area and it is possible to dedicate huge amounts of time to the intricacies of scanning!
#20
ColonelKinkham
You're being told all manner of answers here, and in my opinion many are wrong.
It really depends on what it is that you're scanning, so let's go with an example of scanning a printed photo.
It will almost certainly be printed at 300dpi. That is a fixed value and cannot be changed, no matter what resolution you scan at. If you scan this photo at 300dpi you can have a digital image of the same resolution and quality as the photo itself, although yes use a non-lossy format like tiff (jpeg will compress some colours). You can then print it out at the same size and achieve the same quality as the original (working on the presumption of having the same quality printer...). Scanning this photo at a higher resolution is pointless as there is no extra detail there, it is printed at 300dpi and that is all there is available. Scanning at a higher dpi will not mean that you could print larger versions of the original as the detail is not there. Think of the photo as being a piece of cut fabric, the size is set, you could make it bigger by stretching it but the fabric will distort and stretch. However, it is important to remember that the distance at which a larger print is viewed is further away than that which you view a smaller print, so you may consider the quality acceptable. Either way in this case you can only work with what is available and that is the print resolution; scanning any higher than that will just inflate your file size and contain no extra detail as there is simply no more actually available.
For things that aren't printed options are a little different. Your scanner has a resolution of 1200x2400, meaning that the optical resolution is 1200. Note that this is a theoretical number and most won't actually get close to it, it's more engineering and marketing than an actual value. I for example scan 35mm film and slides and have a dedicated film scanned with a theoretical resolution of 10000dpi, however optically it hits 5000dpi. A drawing using any medium isn't made up of dots of course so you could scan it at whatever size you like, but no more than the optical resolution as you would just be inflating the file size with no benefit. You could scan a drawing at 1200dpi and enlarge it and hence make it much bigger without loss of quality, although you will be restrained by print quality. In this case however I'd save it as a jpeg as you're unlikely to want to store the value of every single pixel/dot.
So, in sum, for already printed items scan at 300dpi as that is a set value based on the print resolution. For non-printed items you might as well scan at a larger dpi but use jpeg formatting and save yourself some space whilst retaining a larger image (in 'physical' pixel terms, if not in file size).
It's a complex area and it is possible to dedicate huge amounts of time to the intricacies of scanning!

Thanks! Appreciate that.
#21
ColonelKinkham
You're being told all manner of answers here, and in my opinion many are wrong.
It really depends on what it is that you're scanning, so let's go with an example of scanning a printed photo.
It will almost certainly be printed at 300dpi. That is a fixed value and cannot be changed, no matter what resolution you scan at. If you scan this photo at 300dpi you can have a digital image of the same resolution and quality as the photo itself, although yes use a non-lossy format like tiff (jpeg will compress some colours). You can then print it out at the same size and achieve the same quality as the original (working on the presumption of having the same quality printer...). Scanning this photo at a higher resolution is pointless as there is no extra detail there, it is printed at 300dpi and that is all there is available. Scanning at a higher dpi will not mean that you could print larger versions of the original as the detail is not there. Think of the photo as being a piece of cut fabric, the size is set, you could make it bigger by stretching it but the fabric will distort and stretch. However, it is important to remember that the distance at which a larger print is viewed is further away than that which you view a smaller print, so you may consider the quality acceptable. Either way in this case you can only work with what is available and that is the print resolution; scanning any higher than that will just inflate your file size and contain no extra detail as there is simply no more actually available.
For things that aren't printed options are a little different. Your scanner has a resolution of 1200x2400, meaning that the optical resolution is 1200. Note that this is a theoretical number and most won't actually get close to it, it's more engineering and marketing than an actual value. I for example scan 35mm film and slides and have a dedicated film scanned with a theoretical resolution of 10000dpi, however optically it hits 5000dpi. A drawing using any medium isn't made up of dots of course so you could scan it at whatever size you like, but no more than the optical resolution as you would just be inflating the file size with no benefit. You could scan a drawing at 1200dpi and enlarge it and hence make it much bigger without loss of quality, although you will be restrained by print quality. In this case however I'd save it as a jpeg as you're unlikely to want to store the value of every single pixel/dot.
So, in sum, for already printed items scan at 300dpi as that is a set value based on the print resolution. For non-printed items you might as well scan at a larger dpi but use jpeg formatting and save yourself some space whilst retaining a larger image (in 'physical' pixel terms, if not in file size).
It's a complex area and it is possible to dedicate huge amounts of time to the intricacies of scanning!

This is wrong.

300dpi only creates a perfect capture of 300dpi if those dots are perfectly aligned. That can be done within the digital realm (so, a screenshot of a screenshot will always be perfect), but not when printing to and then scanning from a photo. That's why it makes sense to oversample, and capture at the maximum real capture res.

Also, at 300dpi, you only get an image that's 1800px across. That isn't even enough to fill a 1080p panel, nevermind a modern 4K display. Expanding the image digitally to fill the display looks a lot worse than shrinking it from an oversampled scan.

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