Scanning slides and negatives at 300dpi versus 3200dpi

I'm scanning slides and negatives I have with a Canon CanoScan that is

capable of up to 3200dpi. I have a couple hundred slides that I want

to scan, but it takes an incredibly long time to scan at 3200dpi. I've

tried scanning some slided at 300dpi for printing at 4x6". Am I

scanning at poor quality if I have the scanner software set to 300dpi

when it can go up to 3200dpi? I chose to scan the slides myself,

because at my local Frontier lag they charge a lot more for this

service than they do regular re-prints. The thing is, I noticed when I

give them a slide, all they do is scan it in and print it. What

settings do they have set on the Frontier's scanner?

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I also have some negatives that I want to scan and make large prints

out of. Is it still a good idea to scan at 300dpi or 3200dpi? My

output resolution of the files that I will send to the printer will be

300dpi. For these files, I am specifying in the Canon scanning

software that I want it to scan the negative and create an 8x12" image

in the file. I've done that with the scanner set to 300dpi at 24-bit

color depth. Should I do the same but at 3200dpi? When I select this

option in the scanner software, it warns me that the file will be

extremely large, in the several hundred megabytes in size. If I want

to make a high quality 8x12" print from a 35mm negative, do I want the

file to be that big?

A 35mm frame scanned at 300 dpi yields roughly a 283 pixel x 425 pixel image which is too small, even for a 4x6 print, since the print resolution would be only about 70 dpi. You need at least 150 dpi for a decent print. The same frame scanned at 3200 dpi gives an image about 3000 pixels by 4500 pixels which is plenty for a high quality 8x12 print at 370 dpi.

Hi, recommend you go to scantips.com for a good explanation of resolution and scanning advice.

I try to think about things from the other end of the logic tree.

 

You want a 4x6 print? What quality? Good is 300 dpi (1200x1800), Average is 150(600x900). You want to scan your negatives to yield that many pixels. If you're going to do any moderate modification, you want 50% or more pixels than you need, and then crop/resize down to the final print size.

Yeah, the file is going to be big, it shouldn't be several hundred megabytes.

 

Are you setting output-size dpi (that is, dpi at 4x6)? IF you are setting dpi at output size,

then yes, 300 dpi is appropriate.

 

If you're setting dpi at original (1 x 1.5) size, then:

 

If you're sure you'll never want to print bigger than (uncropped) 4x6, 1200dpi is about

right. 300 is too little, 3200 is overkill.

 

If you want a quality 8x12, 2400 dpi is reasonable.

Don't confuse input (digital iamge creation) resolution with output (printing) resolution.

 

 

For printing at 300dpi at a 1 dot to 1 pixel ratio (scans and digital images are measured

at pixels per inch, not dots per inch) you would need to scan at a least 1200 ppi but

2400ppi would be better.

 

Printing at 300dpi for a 4"x6' is printing at a low print resolution fo that size print.

 

And GiGo still rules.

This relates to the printing stage.

 

Most commercial lab printers like the fuji frontiers and the noritsu print at 300 dpi or at most 400 dpi. In fact, if you are sending JPEG's to be printed at a frontier, you are expected to resize it based on your required print size at exactly 300dpi. For example if you want a 4x6" print made, the image size needs to be exactly 4x6 times 300dpi which is 1200x1800 pixels. If the image size is different, the frontier resizes the image which has resulted in a less than optimal print from the lab I visit.

 

There is some more information here:

http://www.drycreekphoto.com/Frontier/using_printer_profiles.htm

Printing dpi is not the same as scanning dpi...

 

printing dpi (the usual 300dpi) is number of pixels on the lenght ofone inch on the photo paper

 

Scanning dpi (3200) is the number of pixels you use to "describe" one inch of film

 

If this is 4200F you are talking about (or 8400F) , you will always be better of scanning at 3200 at first, and then resizing your image to an appropriate size. That's because of grain aliasing, it becomes stronger as you scan at a lower resolution. Scans at 3200dpi are the smoothest because you have reached the optical limit of the scanner lens, so the lens softness prevents some of the grain aliasing.

Also noise is usually one pixel in size, so if you scan at 3200 and downsize to 1/2 of that size the one pixel noise gets lost for the most part.

 

Scan at 3200dpi, use your calculator to calculate what size you need

and then change the image size down to that size.

 

You will calculate the size you need by multiplying size in inches with about 300 (the number of dpi the printing machine is working on) I think new frontiers are 320dpi

 

when you scan the image at 3200dpi, it will be around 4500x3000 pixels.

If you wish to make 12 inch long prints, you need 12x320 (12 inch times 320dpi (for fuji frontier)) and that is about 3600 pixels wide image (the longer side).

Just resize your image in photoshop to that size.

"Canon CanoScan" is also just a trade mark; used on many different class of Canon scanners. There is alot of fluff/BS/fibs/make believe in consumer marketed scannera. The name "Canon CanoScan" is old . It is like menetioning a "Ford pickup"; with no reference if it is a Model T; a 1983 Rangerwith a 4 cylinder.; 1995 F100 with a V8. Mention model name and number of your scanner; and some folks here may know what is the <b>practical maximum</b> "dpi scan setting" for you to do a scan at. Many consumer scanners just make bigger files; with no practical increase in usefull detail; when used beyond a certain setting.

There, are currently only two models with 3200dpi resolution,

rest of them are either less or more than that

There are also ancient "Canon CanoScan" flatbeds that have a "3200dpi" setting in software; radically beyond what they can really pull out. The "Canon CanoScan" trademark is really old; and is used for flatbeds; film scanners; even with color copier scan heads. It is like saying a "canon camera"; it might be a 1930's rangefinder; or a 350 dRebel. Since Charles is asking basic scanner questions; I sure would not guess what scanner he is using. There is no information at all. A "3200dpi setting" has been on some older canon ""Canon CanoScan" scanners that are a 1/4 or less in real resolution capability.

<p>IMHO, everybody who said anything besides "1200x1800 for a 4x6 print" really needs to check out <a href="http://www.scantips.com/">Scan tips</a> and pay particular attention to the differences between printer dpi and ppi.

 

<p>While we all know the appeal of large file sizes, I feel this discussion has lost sight of the basic premise of maximizing resources. Just because you <i>can</i> scan everything at your highest resolution does not mean you should. File sizes and processor power should be selected for a specific job in mind, lest you unnessecarily overcycle your processor and reduce the life expectancy of your tools.

Yes, but with these new two flatbeds, 3200dpi does not go for output, that is an imput option, upsampled output goes much beyond that. In my own experience, the dpi setting on 4200F stops making difference in detail somewhere little pass 2400dpi, so I figure this is its optical resolving power. But that doesn't mean that 3200dpi is upsampled from 2400. As I said 3200dpi is an imput option.

Hi Edgar; I guess the point I was getting at is how does one know Charles here really has a 4200F? He might be just using a old flatbed from 1997; that is 800 optical; and has settings at 100,200,400,800,1200,1600,2400,3200dpi. He used the statement <i><b>Canon CanoScan that is capable of up to 3200dpi.</i></b> which is really abit open ended. It probably is a modern scanner; but could just be an old scanner; being used in the make believe stratosphere dpi settings. This is not an argument issue; just clatification on Charles equipment; so he can be steered to a better answer. Since I have had over a dozen scanners; over a decade; I have learned not to assume stuff. Regards to all.

Of course, there is a high possibility that it was not 8400 or 4200

 

And my point was that in case he did mean 3200dpi as input optical resolution setting, and since from the way he was talking I assumed that 3200 is the highest setting in his scanner, that would mean

that he is using a canon scanner with maximum otpical resolution of 3200dpi, and that would leave us with only two choices.

Out of these two, there i greater chance that he owns the cheaper one, so that is where my logic came from :-)

 

Of course all this depends on the assumption that he was talking about 3200dpi optical resolution and not output resolution.

 

But I know what you mean

Hello all and thanks for the input! Actualy, my scanner is a model 8400F. When I prepare a scan, I create the scan image area at or above what I want the size of my print. In this case I am scanning hundreds of slides, 4 at a time. I'm using the flatbed scanner with the provided plastic tool that allows me to place the slides (and negatives) correctly on the glass. This model also has a light on the top part (the part that opens) and projects this light on the back-side of the slide or film as it lays flat on and gets lits from underneath the flatbed area.

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To scan, I am using ScanGear CS and load it from within Photoshop CS. ScanGear CS came with my Canon 8400F scanner. This is exactly what I do for scanning hundreds of color slides that I want to make 4x6" prints out of at a Frontier lab:

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INPUT SETTINGS:

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Select Source: Color Positive Film

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Film Size: 35mm Film Strip

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OUTPUT SETTINGS:

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Color Mode: Color

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Output Resolution: 300 DPI

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Output Size: 1200 x 1800

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IMAGE SETTINGS:

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Auto Tone: OFF

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Unsharp Mask: OFF

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Remove Dust And Scratches: LOW

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With these settings, I got slides that were the correct resolution BUT they were a bit soft. After I scanned them, I did a quick color correction on them and that was it. I realise I should have probably turned unsharpen mask ON on the scanner settings OR have applied unsharpen mask in Photoshop after I did my color correcting, but I was doing hundreds.. so you can imagine.

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In ScanGear CS under Output Resolution I set it at 300 DPI because that is what have heard the Frontier prints at. However, I have the option of selecting up to 3200 DPI. When selecting this option, each slide or negative takes a painfully long time to scan and creates an insanly huge file size.

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I have the option of setting my color to 48-bit, but I figure when scanning hundreds of slides at 4 at a time, this would increase the time required by too much.

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Am I doing thing correctly in this real scenario? When scanning large quantities and you don't have enough time to go through each frame and do lots of work on them, would it be best to just set the unsharp mask feature on the scanner to ON to avoid getting slightly soft faces in my pictures?

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Now, if I want to scan an image that I want to create an 8x12" print out of a 35mm slide or negative, what should I change in my scenario to do this? In this case, I would spend a LOT more time on each frame.

I should ad that I do not know about INPUT RESOLUTION on the 8400F scanner because it does not give me that option in ScanGear CS.

<i> OR have applied unsharpen mask in Photoshop after I did my color correcting, but I

was doing hundreds.. so you can imagine.

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So set up a Photoshop action to do the unsharp masking. It should easily be able to plow

through a hundred or two overnight. Do this on duplicates (or save to a new location) so

you won't hose your original scans if something goes wrong.

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An even better, but slower, workflow would be to scan at 600 (at 4x6), do 80% of your

USM at that size, downsample to 300, and do a little more USM before saving. Photoshop

bicubic downsampling is better than the bilinear or nearest neighbor resample that the

scanner is doing. This way you'll have a bunch of files appropriately sized for 4x6, but

you'll also have files you can go back to for 8x12s without rescanning.