Scanner Resolution

Curt · Feb 28, 2010

I've had the 4990 for a week and have been scanning at 1200, what should I be setting in as a starter when making digital negatives for Pt/Pd & Carbon? Obviously I've had to dummy it down for uploads to the web but the actual production of a digital negative is more important to me. I hate to ask such questions but this is a new venture for me as is Carbon and Pt/Pd.

A recent workshop in Carbon and Pt/Pd really opened up my eyes after seeing digital negatives being made for the two processes. I wish there had been a third day on digital negative production. Special thanks to Per, Don and Jim.

Thanks for any help,
Curt

sanking · Mar 1, 2010

Curt said:
I've had the 4990 for a week and have been scanning at 1200, what should I be setting in as a starter when making digital negatives for Pt/Pd & Carbon?
Thanks for any help,
Curt

Curt,

As a general rule you want to scan at a high enough resolution so that your final file has at least 360 ppi at the size you want to print your digital negative.

For example, if you scan a 4X5" negative and want to make a final print 8X10" in size you should scan at a minimum of 720 ppi. That way, when you enlarge the 4X5" file to 8X10" you will have resolution of 360 ppi.

That is not the way I work however as I generally scan to archive. That is, I scan a negative at the highest practical resolution, then make all global corrections and changes to the file, and save this file as the master. Then, when I want to print I reload the file and downsize it to whatever print size I want. However, with the 4990 there is no need to scan at higher resolution of 2400 ppi since this will not give you more resolution than scanning at 2400 spi. So I would scan the 4X5" negative at 2400 spi, correct it as the master, and then save. This would allow you to print at the following sizes.

8X10 -- 1200 ppi
16X20 -- 600 ppi
32X40-- 300 ppi

Course, there is no reason to print at resolution higher than 360 ppi since you will not see it.

Sandy King

pellicle · Mar 1, 2010

Sandy

I'm not sure how well experienced the OP is, but when starting out I read SPI and DPI and PPI I wonderd what they all mean. I do realise the differences but since a sample is really just a way of saying point (that boils down to a pixel or a Cartesian grid reference) does mixing all the terms provide benefit of confusion?

its like in my research area of water, people mix cubic feet, cubic meters, mega liters all in the same report proporting to be discussing a topic with the intention of making things clear.

sanking · Mar 1, 2010

pellicle said:
Sandy

I'm not sure how well experienced the OP is, but when starting out I read SPI and DPI and PPI I wonderd what they all mean. I do realise the differences but since a sample is really just a way of saying point (that boils down to a pixel or a Cartesian grid reference) does mixing all the terms provide benefit of confusion?

its like in my research area of water, people mix cubic feet, cubic meters, mega liters all in the same report proporting to be discussing a topic with the intention of making things clear.

OK, to clarify.

For scanned images or bit-mapped images the correct term is spi (samples per inch).

For display resolution the correct term is ppi (pixels per inch).

However, most people use ppi and spi interchangeably to mean the same thing.

Device resolution may be expressed as either spi or dpi (dots per inch) but it is not part of the image at all. It is the resolution of the output device. The resolution of Epson inkjet printers may be 1440 dpi or 2880 dpi, or even greater. For best results I recommend setting the printer resolution at the highest possible resolution setting (though this may not be optimum in terms of printing speed) and sending the printer an image file that is at least 360 ppi in size at the printing size.

Sandy King

pellicle · Mar 1, 2010

Hi Sandy

I am unsure if my meaning was obscure and unclear

sanking said:
OK, to clarify.

However, most people use ppi and spi interchangeably to mean the same thing.

yes, that was my point ... and so the whole thing can be simplified as DPI

Loris Medici · Mar 1, 2010

Nope, dpi is a completely different animal in my book. The most common mistake made in digital photography is confusing dpi with ppi.

spi/ppi are kinda similar indeed...

pellicle said:
...the whole thing can be simplified as DPI

pellicle · Mar 1, 2010

Loris Medici said:
Nope, dpi is a completely different animal in my book. The most common mistake made in digital photography is confusing dpi with ppi.

would you be so kind as to explain it?

Loris Medici · Mar 1, 2010

http://en.wikipedia.org/wiki/Dots_per_inch

Loris Medici · Mar 1, 2010

And would you please follow the link to "pixels per inch" from there? (See section "Scanners and cameras" in the 2nd page...)

Curt · Mar 1, 2010

sanking said:
Curt,

As a general rule you want to scan at a high enough resolution so that your final file has at least 360 ppi at the size you want to print your digital negative.

For example, if you scan a 4X5" negative and want to make a final print 8X10" in size you should scan at a minimum of 720 ppi. That way, when you enlarge the 4X5" file to 8X10" you will have resolution of 360 ppi.

That is not the way I work however as I generally scan to archive. That is, I scan a negative at the highest practical resolution, then make all global corrections and changes to the file, and save this file as the master. Then, when I want to print I reload the file and downsize it to whatever print size I want. However, with the 4990 there is no need to scan at higher resolution of 2400 ppi since this will not give you more resolution than scanning at 2400 spi. So I would scan the 4X5" negative at 2400 spi, correct it as the master, and then save. This would allow you to print at the following sizes.

8X10 -- 1200 ppi
16X20 -- 600 ppi
32X40-- 300 ppi

Course, there is no reason to print at resolution higher than 360 ppi since you will not see it.

Sandy King

Thank you Sandy I've made a note of the information you provided.

Curt

pellicle · Mar 1, 2010

Loris Medici said:
http://en.wikipedia.org/wiki/Dots_per_inch

yes, its good that you quote that ... it does not however counter my point. I'm suggesting that from an abstract point of view they are indeed such similar notions as to require a specific context to separate them.

my model of thinking (you know, models, like how we understand light, is it a wave or a particle) is that the digital file is the center and aquisition and printing are both spokes out from that.

If discussing resolution and sampling of scanners then SPI is more significant when understanding how fine details which are at or lower than the sampling will be effected. The same goes for printing, and undstanding what happens there.

About twenty years ago in science I was totally pedantic as to usage of terms today I assume that noone truly understands what the terms mean and so I'm far more comfortable with generalisations unless reading scientific papers. If a discussion seems to be drifting due to a misunderstanding of terms I then bring them into discussion and determine the other partys congruence with terms before moving on.

Loris Medici · Mar 2, 2010

Everyone who takes the trouble of reading a little bit - or my students (at least) - understand the *terms* exactly and use them appropriately.

pellicle · Mar 2, 2010

Loris Medici said:
Everyone who takes the trouble of reading a little bit - or my students (at least) - understand the *terms* exactly and use them appropriately.

good, but not everyone who posts here is one of your students ...

Loris Medici · Mar 2, 2010

pellicle, here we're eachother's instructor and student in the same time; we learn from eachother and we teach to eachother. That's the main purpose of the forum, don't you think?

Now, I'll be glad if I managed to make you grasp the difference between dpi and ppi/spi as the conclusion of our exchange. My motivation was your statement below:

pellicle said:
...when starting out I read SPI and DPI and PPI I wonderd what they all mean...

I hope there is no more confusion at your part now. Tell me if you need me to further elaborate...

Regards,
Loris.

pellicle · Mar 2, 2010

Loris Medici said:
pellicle, here we're eachother's instructor and student in the same time; we learn from eachother and we teach to eachother. That's the main purpose of the forum, don't you think?

exactly, it is the reason I participate. Just FYI I have been clear about the meanings for well over ten years, that wasn't however the basis for what I was asking about.

sanking · Mar 2, 2010

pellicle said:
If a discussion seems to be drifting due to a misunderstanding of terms I then bring them into discussion and determine the other partys congruence with terms before moving on.

I personally believe that there is a far greater risk of confusion and misunderstanding when terms are not used appropriately and correctly than otherwise. And in this case spi, ppi and dpi have very precise meanings, even though people sometimes use them interchangeably. But from the perspective of someone who taught at the university level for more than three decades I prefer to use terms correctly and precisely and leave the responsibility for understanding to the reader.

Sandy King

Curt · Mar 3, 2010

When the OP comes across a term that he does not recognize he looks it up to find its meaning and usage and by do so increases his knowledge. Following the ideas of this thread he gets the gist of the matter.

He now has a simple plan for a simple task that fits into a highly complex technical World with a multitude of unconnected intersections of disparate technologies.

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