Scanners

Can anyone tell me what is ment by 600x1200 or 1200 x 2400 when you are talking about scanners dpi.

What does the first number stand for and what does the second nuber stand for.

I was told that, in the case of a 1200x 2400 the 1200 means colour and the 2400 means black and white

please let me know
thanks
--Steve Martin

Steve Martin said:

Can anyone tell me what is ment by 600x1200 or 1200 x 2400 when you
are talking about scanners dpi.

What does the first number stand for and what does the second nuber
stand for.

I was told that, in the case of a 1200x 2400 the 1200 means colour
and the 2400 means black and white

please let me know
thanks

--
Steve Martin

Click to expand...

Steve,

The numbers represent a matrix of horizontal and vertical pixels within a one square inch border used to capture information. The higher the total number of pixels used in a capture, the more detail which can be resolved.

Having said this, there are practical limitations and the number of pixels needed for a good representative photo varies according to the nature of the subject material. For example, it would take far fewer pixels to accurately represent a white wall with little or no texture than to capture the brilliant hues and variations of color and texture on a butterfly's wings.

Just think of it as an array of "sensors" in regular patterns - so many across and so many down.

Lin

Lin Evans said:

Steve Martin said:

Can anyone tell me what is ment by 600x1200 or 1200 x 2400 when you
are talking about scanners dpi.

What does the first number stand for and what does the second nuber
stand for.

I was told that, in the case of a 1200x 2400 the 1200 means colour
and the 2400 means black and white

please let me know
thanks

--Lin What I should have asked I an thinking for buyin a new scanner

Click to expand...

Click to expand...

I an wondering if I should get a 2400x 2400 dpi scanner or a 1200x1200 scanner I want to scan a lot of 35 mm negs and slides..
would the 2400x2400 be better???

Member said:

Member said:

Steve Martin

Click to expand...

Steve,
The numbers represent a matrix of horizontal and vertical pixels
within a one square inch border used to capture information. The
higher the total number of pixels used in a capture, the more
detail which can be resolved.

Having said this, there are practical limitations and the number of
pixels needed for a good representative photo varies according to
the nature of the subject material. For example, it would take far
fewer pixels to accurately represent a white wall with little or no
texture than to capture the brilliant hues and variations of color
and texture on a butterfly's wings.

Just think of it as an array of "sensors" in regular patterns - so
many across and so many down.

Lin

Click to expand...

Steve Martin said:

Lin Evans said:

Steve Martin said:

Can anyone tell me what is ment by 600x1200 or 1200 x 2400 when you
are talking about scanners dpi.

What does the first number stand for and what does the second nuber
stand for.

I was told that, in the case of a 1200x 2400 the 1200 means colour
and the 2400 means black and white

please let me know
thanks

--Lin What I should have asked I an thinking for buyin a new scanner

Click to expand...

Click to expand...

I an wondering if I should get a 2400x 2400 dpi scanner or a
1200x1200 scanner I want to scan a lot of 35 mm negs and slides..
would the 2400x2400 be better???

Click to expand...

Steve,

The 2400x2400 would be better, but if all you are planning to scan are slides, you might consider a dedicated slide scanner rather than a flatbed scanner with a slide attachment. Professional equipment scans go a high as 4000 dpi, but usually begin to collect film grain and many good scans have been made at 2400x2400. Remember on other factor - optical scan resolution versus "interpolated" or software enhanced resolution. Optical resolution of 2400x2400 might be quite sufficient.

Lin

Lin Evans said:

Steve Martin said:

Lin Evans said:

Steve Martin said:

Can anyone tell me what is ment by 600x1200 or 1200 x 2400 when you
are talking about scanners dpi.

What does the first number stand for and what does the second nuber
stand for.

I was told that, in the case of a 1200x 2400 the 1200 means colour
and the 2400 means black and white

please let me know
thanks

--Lin What I should have asked I an thinking for buyin a new scanner

Click to expand...

Click to expand...

I an wondering if I should get a 2400x 2400 dpi scanner or a
1200x1200 scanner I want to scan a lot of 35 mm negs and slides..
would the 2400x2400 be better???

Click to expand...

Steve,
The 2400x2400 would be better, but if all you are planning to scan
are slides, you might consider a dedicated slide scanner rather
than a flatbed scanner with a slide attachment. Professional
equipment scans go a high as 4000 dpi, but usually begin to collect
film grain and many good scans have been made at 2400x2400.
Remember on other factor - optical scan resolution versus
"interpolated" or software enhanced resolution. Optical resolution
of 2400x2400 might be quite sufficient.

Lin

Click to expand...

The scanner I was looking at was the new Hp Scanjet 5470 c
2400 x 2400 hardware
It has to be better than the Umax 2200 (600 Dpi)

Steve

Steve Martin said:

Can anyone tell me what is ment by 600x1200 or 1200 x 2400 when you
are talking about scanners dpi.

What does the first number stand for and what does the second nuber
stand for.

Click to expand...

Steve --

Lin has given you a good description of the pixel matrix represented by this notation. To answer your particular question as to what the first and second numbers mean respectively, the first indicates horizontal resolution (along the length of the sensor array which lies perpendicular to the scan direction), and the second is the resolution along the scan path ("vertical" for a typical A4 scanner). The first figure actually tells you the fundamental optical resolution of the photoreceptor array -- i.e. a 1200 x 2400 scanner is basically a 1200 ppi device. You will often see the second figure as double the first, and this is achieved mechanically by "half stepping" the scan head so that the distance between scan lines is half the sensor's optical resolution. This allows a quite effective form of interpolation to be used to increase the vertical resolution. Don't confuse this with the software interpolation used to permit the claims of 9600 x 9600 ppi that you will often see. Utilising this "resolution" gains you nothing at all and produces enormous file sizes.

As a guide, for photographic images you'd never need more than 360 ppi at the final enlarged image dimensions (and in most cases quite a bit less will suffice). While small negs or transparencies will obviously need to be scanned at proportionately higher resolution, 1:1 reproductions (typically from reflective originals on a flatbed scanner) will only need really high resolution settings when scanning "line art" -- pen drawings, text for direct reproduction, etc.

Steve Martin said:

I was told that, in the case of a 1200x 2400 the 1200 means colour
and the 2400 means black and white

Click to expand...

With all due respect to whoever told you that, it would have to be the most misinformed interpretation I've yet heard. Colour definition is determined by the "bit depth" you select. It sets the degree of subtlety with which the colour of each pixel is recorded (and hence the size of the resulting file), not how many pixels there are in total, or per inch.

Mike

Steve Martin said:

The scanner I was looking at was the new Hp Scanjet 5470 c
2400 x 2400 hardware
It has to be better than the Umax 2200 (600 Dpi)

Click to expand...

Yes -- for scanning 35 mm originals, no contest. If you were only going to scan large existing prints, on the other hand, the added resolution of the ScanJet would be completely wasted.

I mentioned 360 ppi as a maximum practical figure for the final photographic image, but at the low end 200 ppi is considered quite workable. For a 35 mm original (36 x 24 mm = 1.42" x 0.94"), scanning at 2400 x 2400 would blow it up to 2400/200 times this, i.e. a final print size of about 17" x 11". The 600 ppi scan would only allow a print of about 4.5" x 3" at the same 200 ppi output resolution.

Mike

The gentlemen before me have gone into the technicalities in sufficient detail.

For some practical experience, I have used a HP7400C (2400dpi) with great success on 35mm negatives and slides. This scanner includes the same backlight unit as the HP5470C.

The results are great, but I wouldn't go for a lower optical resolution than 2400dpi. These image are pretty small!

The results are probably good enough for an amateur. As a professional, you may want to get a dedicated slide scanner (4000dpi).