Resolution, Image Size

Alex_B

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fmw said:
When a client asked me for 400 dpi, he was asking me for a higher resolution scan of my transparencies.

Yes, but that client would know that a 400 ppi scan from 35mm would mean a totally different thing than a 400 ppi scan from medium format.

So the client would translate (maybe he was not aware of this though) the ppi plus the format into total pixels times pixels.
 

Alex_B

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oh, and another thing, 200 dpi for the printing output can look very nice still, and if you go to real large format printing, even 100 dpi or much less can do a fine job ... you just don't view that 30 by 30 ft outdoor print from 30 inches pixel peeping distance ;)
 

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I still scan negatives on a daily basis and you are absolutely correct. You set the scanner in dpi which in effect determines the resolution.

Once you have the pixel count for all intents and purposes dpi is moot. Until you buy a printer then the higher the dpi the better the print but that still doesn't have any effect on the image itself. It's all in the pixel count once it is a digital file, or so say the people at the lab. If your print is wet process photo toss dpi out completely it is irrelivant.

Dpi in a print is only for dot type printers ink, lazer, and even matrix types. The scanners are actually more designed for text originally than images, so setting them up in dpi made sense. It was going directly to a digital printer in almost all the cases now it is tradition, I guess.
 

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mysteryscribe said:
I still scan negatives on a daily basis and you are absolutely correct. You set the scanner in dpi which in effect determines the resolution.

In my scanning software you actually have both displayed, the ppi and the total pixels, which i quite like as I don't have to do the maths myself then ;)
 

fmw

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Alex_B said:
Yes, but that client would know that a 400 ppi scan from 35mm would mean a totally different thing than a 400 ppi scan from medium format.

So the client would translate (maybe he was not aware of this though) the ppi plus the format into total pixels times pixels.

No, scanning is the same as the format difference in the first place. A 400 dpi scan of 6X7 transparency will have more pixels by far than one from a 35mm transparency - just like a large format transparency will have more resolution on film than a 35mm one. Same with a direct digital shot.

The 400 dpi stays constant, the pixel count changes by the size of the item scanned. Sometimes you crop when you scan so the file size or pixel count may not be the same on every scan of the same format. Yes, the art director would certainly know that.

I was just exlaining that the fellow that wrote the article may not have understood himself what the client asked for when he asks for dpi. It was very common in the 90's. I assume that sort of thing is now obselete. There was a time when every pro shot film and every art director wanted a digital file for Photoshop. It was like that for several years before pros started shooting direct to digital.
 

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mysteryscribe said:
I just scan at the highest resolution and shrink it if i need to. I'm a math cripple.

A Good plan but it can be time consuming. I used to consider taking naps while I scanned 4X5" Ektachromes at high (at the time) resolution.
 

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fmw said:
No, scanning is the same as the format difference in the first place. A 400 dpi scan of 6X7 transparency will have more pixels by far than one from a 35mm transparency - just like a large format transparency will have more resolution on film than a 35mm one. Same with a direct digital shot.

The 400 dpi stays constant, the pixel count changes by the size of the item scanned. Sometimes you crop when you scan so the file size or pixel count may not be the same on every scan of the same format. Yes, the art director would certainly know that.

I was just exlaining that the fellow that wrote the article may not have understood himself what the client asked for when he asks for dpi. It was very common in the 90's. I assume that sort of thing is now obselete. There was a time when every pro shot film and every art director wanted a digital file for Photoshop. It was like that for several years before pros started shooting direct to digital.
The original poster asked about dpi coming from a digital camera. It's meaningless in that case. In the case of scanning, it only means something if you know what the original size was. Some pro shops would only tell people that they needed a 300dpi file. This doesn't help, because they might submit one that came from a disc camera neg. Pixel count will tell you how far you can enlarge an image.

The 400 dpi may be constant, but the quality isn't. That's why dpi alone doesn't tell you anything.
 

Alex_B

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fmw said:
No, scanning is the same as the format difference in the first place. A 400 dpi scan of 6X7 transparency will have more pixels by far than one from a 35mm transparency -

I did not say anything to contradict your post :) Actually, what you say here is the same as waht I said ;) I do not understand the "no" here ;)

I was only saying that your clients will understand that larger format with same PPI scanning means a higher total pixelcount (and therefore better usability in large format print later).

I guess we all mean the same and just have a collision of vocabulary and anticipations here ;)

cheers.
 

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markc said:
Some pro shops would only tell people that they needed a 300dpi file. This doesn't help,

Wrong, it does help, as when you want something printed, you want it printed at a certain size. so some pro shops want 300 dpi for a given output size.

Of course that dpi number has nothing to do with the random dpi/output size combination which might be assigned to your picture by the camera, or your graphics program or whatever.

as the pro shop prints, in printing the dpi havea meaning.
 

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Less than nothing mark it is misleading... a 600 dpi scan of a thirtyfive mm neg is barely enough to make an 8x10 and I mean barely.... I scan mine at 1800 and it make a decent 8x10 frm 35mm I'm not thinking of going any highter..

I can remember scanning images when it was necessary to go to the edges with a soft brush to wipe out the pixelization. It has come a long way and is more than enough for the kind of photography I did at the end of my career.
 

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markc said:
The original poster asked about dpi coming from a digital camera. It's meaningless in that case. In the case of scanning, it only means something if you know what the original size was. Some pro shops would only tell people that they needed a 300dpi file. This doesn't help, because they might submit one that came from a disc camera neg. Pixel count will tell you how far you can enlarge an image.

The 400 dpi may be constant, but the quality isn't. That's why dpi alone doesn't tell you anything.

I was referring to the internet article to which someone had posted a link, not to printing dpi embedded in a digital image. The fellow was smearing clients for asking for dpi. It was very common to do things that way 10 years ago. Today we use dpi to refer to printing. 10 years ago it was used also to refer to scanning.

The quality of a 400 dpi scan is not constant because the area to be scanned can differ. Scanning a 4X5 transparency at 400 dpi and scanning a 35mm slide at 400 dpi are very different things with different resolutions and different file sizes. That was the whole point I was trying to make. Apparently, I didn't make it very well.
 

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Alex_B said:
Wrong, it does help, as when you want something printed, you want it printed at a certain size. so some pro shops want 300 dpi for a given output size.
That's what I was saying. If you have a dpi and a given output size, you have uselful information. If you have only dpi, you don't. In the same way that mph doesn't tell you how quick a trip will take unless you know the distance.
 

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fmw said:
Today we use dpi to refer to printing. 10 years ago it was used also to refer to scanning.
Yeah, it's probably an old article. But dpi still used for both. I'd say scanning is even more common today with so many labs scanning film and printing digitally.

The quality of a 400 dpi scan is not constant because the area to be scanned can differ. Scanning a 4X5 transparency at 400 dpi and scanning a 35mm slide at 400 dpi are very different things with different resolutions and different file sizes. That was the whole point I was trying to make. Apparently, I didn't make it very well.
Sorry. Yeah, I agree. It was the same point I was trying to make. And I still think it's meaningless in a file. It means something at the time of scanning and at the time of printing, since that's the only time "inches" come into play. A file is just pixels.
 

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nice that we all agree :)

and did so from the beginning ;)
 

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