Sign up now! · Forgot password?
RSS/Atom feed Twitter

what is optical resolution

This discussion is connected to the gimp-user-list.gnome.org mailing list which is provided by the GIMP developers and not related to gimpusers.com.

7 of 8 messages available
Toggle history

Please log in to manage your subscriptions.

what is optical resolution Amit Mukherjee 12 Apr 07:49
  what is optical resolution Roland Roberts 12 Apr 17:49
  what is optical resolution Guillermo S. Romero / Familia Romero 12 Apr 18:29
   what is optical resolution Roland Roberts 12 Apr 20:21
E7F20B466062D511973800508B6... 07 Oct 20:15
  what is optical resolution Guillermo S. Romero / Familia Romero 12 Apr 19:27
  what is optical resolution Roland Roberts 12 Apr 20:10
  what is optical resolution Roland Roberts 12 Apr 20:18
Amit Mukherjee
2002-04-12 07:49:14 UTC (over 19 years ago)

what is optical resolution

Hi,
Can anyone explain to me what optical resolution means. I am looking at the product specification of an Epson scanner and it says that the optical resolution is 1600x3200 dpi. What does this mean ?

The software that comes with the scanner I have gives me a choice to scan upto 9600 dpi. How do I know whether this value is the optical resolution or the software interpolated resolution ?

Thanks Amit

Get fast and easy Internet access through http://www.netkracker.com

Roland Roberts
2002-04-12 17:49:08 UTC (over 19 years ago)

what is optical resolution

"Amit" == Amit Mukherjee writes:

Amit> Can anyone explain to me what optical resolution means. I am Amit> looking at the product specification of an Epson scanner and Amit> it says that the optical resolution is 1600x3200 dpi. What Amit> does this mean ?

Optical resolution is the real resolution of the scanner. Anything higher is interpolated and you can do at least as well in the GIMP as the scanner will do.

Generally, I don't count on anything higher than the lower number; i.e., for your case, I treat 1600x3200dpi as 1600dpi.

And to avoid the whole problem with asymmetric resolution, I just bought an Epson Perfection 2450 Photo scanner with 2400dpi optical resolution. We used to have an (old) Scanmaker E3 with 300x600dpi optical resolution, but I found trying to operate it at 300x600 instead of 300x300 just caused little jaggies in the results; I don't think the stepper motors were doing a good job position the platform. Newer scanners should do better, but I still prefer the scanners with resolution the same in both directions.

roland

Guillermo S. Romero / Familia Romero
2002-04-12 18:29:18 UTC (over 19 years ago)

what is optical resolution

amitmukh@netkracker.com (2002-04-12 at 0549.14 +0000):

Can anyone explain to me what optical resolution means. I am looking at the product specification of an Epson scanner and it says that the optical resolution is 1600x3200 dpi. What does this mean ?

It means the scanner can "see" that many real dots, it can sample that info from the documents directly. In digital cameras the concept is similar, the good thing is optical zoom, not digital zoom, cos it performs the operation directly, not as post process or similar tricks.

Internally the hardware have some elements, not necessarily matching the pixels you will get, but arranged and designed in such a way that the maximum optimum number of pixels is what "optical resolution" says.

The software that comes with the scanner I have gives me a choice to scan upto 9600 dpi. How do I know whether this value is the optical resolution or the software interpolated resolution ?

If it is above optical specs, it is interpolated. I can think a case in which app wants to give mid resolution at high speed, and scans at low resolution and then fakes... which is a nasty trick. This trick should not happen when using maximum quality settings with less or equal resolution than declared "optical".

In some scanners interpolated is (a bit) better than scaling the image afterwards, cos the driver has access to the full range of info (some scan in 30 bits vs 24 of images, for example) as well as knowing how it is made the hardware and thus can guess better. But you should always pay attention to optical, it is the real limit, other things are tricks.

GSR

Guillermo S. Romero / Familia Romero
2002-04-12 19:27:31 UTC (over 19 years ago)

what is optical resolution

john.j.cruz@baesystems.com (2002-04-12 at 1217.06 -0400):

I don't currently have a digital camera. I use the new Kodak format and for

What Kodak format? Are you talking about typical relfex camera with 35mm film or another thing?

the developing process I request digitized photos. I don't now recall the size of each photo-file return (via CD) but I think each photo-file is a jpeg file under 1 Meg.

And in pixels? That is what really counts... and well, they could give you too something better than JPEG too (aka something lossless).

So my real question is should I buy a $200 HP camera at 1.3 Meg pixels or a $ 200 HP scanner?

If you can afford the development costs (both negative and a mid/small size paper copy), the scanner. Also film has better range.

GSR

Roland Roberts
2002-04-12 20:10:30 UTC (over 19 years ago)

what is optical resolution

"jjc" == Cruz, John J writes:

jjc> Roland, You certainly have answered most of the questions I jjc> had in mind. I do have one remaining question, however. The jjc> digital cameras I've seen at stores like CompUSA only list in jjc> their spec. total pixels. For example 1.3 Meg pixels. My jjc> question is how can I translate this number to the print size jjc> I want to print (w/o perceptible distortion)? I print all jjc> photos on 8.5" x 11" photo paper and would like to print also jjc> at 17" x 22".

The more common formats in digital camera are a 4:3 ratio, at least for the smaller formats. I have a 1.3 megapixel camera and it's formats are 320x240, 640x480, and 1280x960. Higher end cameras may do other things. Do a little more digging, you should be able to find something about the actual formats supported for your camera.

jjc> I don't currently have a digital camera. I use the new Kodak jjc> format and for the developing process I request digitized jjc> photos. I don't now recall the size of each photo-file jjc> return (via CD) but I think each photo-file is a jpeg file jjc> under 1 Meg.

jjc> So my real question is should I buy a $200 HP camera at 1.3 jjc> Meg pixels or a $ 200 HP scanner?

What's the resolution of the scanner?

A 1.3 megapixel camera will never produce satisfactory prints at 17x22 and, even though Ofoto (http://www.ofoto.com) claims it will print at 8x10, the quality if marginal. Acceptable for a family vacation photo, maybe, but not for critical work. Mind you, we bought a Fuji FinePix 1400 1.3 megapixel camera last year for vacation pictures where we expect to (1) put them on the web for our family members to view and (2) occasionally make 4x6 snapshot-sized prints for friends/relatives. For 8x10 prints, I wouldn't recommend anything less than a 2 megapixel camera, but again, that is primarily for non-critical work.

I'd say spend the money on the printer if you are doing artwork. Even an inexpensive color printer is acceptable for proofs. My dad does commercial work and he considers his Tektronix Phaser (don't remember which model) only acceptable for proofs. For high quality, it goes to a service bureau.

roland

Roland Roberts
2002-04-12 20:18:29 UTC (over 19 years ago)

what is optical resolution

"jjc" == Cruz, John J writes:

jjc> So my real question is should I buy a $200 HP camera at 1.3 jjc> Meg pixels or a $ 200 HP scanner?

I just reread this and realized you asked about a _scanner_ not a printer. Sorry, I've been thinking of buying a color printer, so my brain was on the wrong track.

I'd buy the scanner. If you can double you budget, I'd still buy the scanner. My Epson Perfection 2450 Photo scanner cost me about $360 and scans a 35mm slide at better than 6-megapixels. I use it for my hobby (astrophotography) where I can rarely trust the lab to print an acceptable result.

In general, paper doesn't have the same dynamic range as film, so scanning from prints doesn't get you the same results as scanning from film. Still, scanning a 4x6 print at 1600dpi (the figure you originally mentioned) should allow you to print at 17x22 and still have 300dpi. You may have to do some work to sharpen up the scan, but it might work. Not having gone past an 8x10, I'm not the right person to ask for how _well_ it will work.

The bigger problem is that the GIMP will only handle 8-bits/color which means you can't take full advantage of your scanner. From the rumors I've heard, this will change in GIMP 2, but I've also heard not to expect to see that for another year.

roland

Roland Roberts
2002-04-12 20:21:02 UTC (over 19 years ago)

what is optical resolution

"Guillermo" == Guillermo S Romero / Familia Romero writes:

Guillermo> In some scanners interpolated is (a bit) better than Guillermo> scaling the image afterwards, cos the driver has access Guillermo> to the full range of info (some scan in 30 bits vs 24 Guillermo> of images, for example) as well as knowing how it is Guillermo> made the hardware and thus can guess better. But you Guillermo> should always pay attention to optical, it is the real Guillermo> limit, other things are tricks.

Actually, this is a good point which I forgot. I've been using software other than the GIMP for initial processing (mostly level adjustment) to access the full 16-bits/color from my scanner, then doing touch-up in the GIMP. Having access to all 16-bits/color would be a great thing to have in the GIMP....

roland