megapixel

dimensions

dpi

raw
size
in megabytes

300 dpi picture size

0.3

640

x

480

554

0.9

2.1

x

1.6

0.4

768

x

576

665

1.3

2.6

x

1.9

0.8

1024

x

768

887

2.3

3.4

x

2.6

1.0

1152

x

864

998

2.9

3.8

x

2.9

1.1

1216

x

912

1053

3.2

4.0

x

3.0

1.2

1280

x

960

1109

3.5

4.3

x

3.2

1.3

1280

x

1024

1145

3.8

4.3

x

3.4

1.4

1344

x

1024

1173

3.9

4.5

x

3.4

1.4

1280

x

1084

1178

4.0

4.3

x

3.6

1.5

1520

x

1008

1238

4.4

5.0

x

3.4

1.6

1536

x

1024

1254

4.5

5.1

x

3.4

1.6

1472

x

1104

1275

4.7

4.9

x

4.7

1.7

1360

x

1234

1295

4.8

4.5

x

4.1

1.9

1600

x

1200

1386

5.5

5.3

x

4.0

2.0

1728

x

1152

1411

5.7

5.8

x

3.8

2.0

1632

x

1232

1418

5.8

5.4

x

4.1

2.0

1760

x

1168

1434

5.9

5.9

x

3.9

2.1

1792

x

1200

1466

6.2

6.0

x

4.0

2.1

1800

x

1200

1470

6.2

6.0

x

4.0

2.3

1901

x

1212

1518

6.6

6.3

x

4.0

2.3

1712

x

1368

1530

6.7

5.7

x

4.6

2.6

1856

x

1392

1607

7.4

6.2

x

4.6

2.6

2000

x

1312

1620

7.5

6.7

x

4.4

2.7

1984

x

1360

1643

7.7

6.6

x

4.5

3.0

1984

x

1488

1718

8.5

6.6

x

5.0

3.0

2016

x

1512

1746

8.7

6.7

x

5.0

3.1

2032

x

1524

1760

8.9

6.8

x

5.0

3.1

2048

x

1536

1774

9.0

6.8

x

5.1

3.1

2160

x

1440

1764

8.9

7.2

x

4.8

3.4

2268

x

1512

1852

9.8

7.6

x

5.0

3.8

2240

x

1680

1940

10.8

7.5

x

5.6

3.8

2272

x

1680

1954

10.9

7.6

x

5.6

3.8

2400

x

1600

1960

11.0

8.0

x

5.3

3.9

2272

x

1704

1968

11.1

7.6

x

5.7

3.9

2288

x

1712

1979

11.2

7.6

x

5.7

3.9

2304

x

1704

1981

11.2

7.7

x

5.7

3.9

2304

x

1712

1986

11.3

7.7

x

5.7

4.0

2304

x

1728

1995

11.4

7.7

x

5.8

4.0

2448

x

1632

1999

11.4

8.2

x

5.4

4.0

2464

x

1648

2015

11.6

8.2

x

5.5

4.3

2400

x

1800

2078

12.4

8.0

x

6.0

4.9

2560

x

1920

2217

14.1

8.5

x

6.4

4.9

2540

x

1932

2215

14.0

8.5

x

6.4

5.0

2592

x

1944

2245

14.4

8.6

x

6.5

5.1

2608

x

1952

2256

14.6

8.7

x

6.5

5.9

3008

x

1960

2428

16.9

10.0

x

6.5

6.0

3008

x

2000

2453

17.2

10.0

x

6.7

5.9

2816

x

2112

2439

17.0

9.4

x

7.0

6.0

2832

x

2128

2455

17.2

9.4

x

7.0

6.0

3032

x

2008

2467

17.4

10.1

x

6.7

6.1

2856

x

2142

2473

17.5

9.5

x

7.1

6.2

2872

x

2160

2491

17.7

9.6

x

7.2

6.3

3072

x

2048

2508

18.0

10.2

x

6.8

7.0

3072

x

2304

2660

20.3

10.2

x

7.7

7.1

3264

x

2176

2665

20.3

10.9

x

7.3

8.0

3264

x

2448

2827

22.9

10.9

x

8.2

8.2

3504

x

2336

2861

23.4

11.7

x

7.8

8.3

3350

x

2482

2884

23.8

11.2

x

8.3

11.0

4064

x

2704

3315

31.4

13.6

x

9.0

12.1

4256

x

2848

3482

34.7

14.2

x

9.5

12.3

4048

x

3040

3508

35.2

13.5

x

10.1

13.5

4500

x

3000

3674

38.6

15.0

x

10.0

16.6

4072

x

4072

4072

47.4

13.6

x

13.6


The charts to the left and below allow one to cross reference pixels and certain popular dpi settings. The image size can be obtained from the image size window in any of the major image editing programs like Photoshop when the image is open. This will give the dimensions in pixels. These figures can then be cross referenced using this chart. For the purpose of these discussions all calculations are considered without interpolation.
For sales reasons manufacturers do not clearly explain the relationship between megapixels and dpi on lower end 35mm negative scanners. The use of the pixel itself as a unit of measure is not consistent with higher end scanners. Remember that printers, scanners, and monitors all can be set to various size dots or pixels. The pixel is the smallest addressable screen element, it is the smallest unit of picture which can be controlled. It is the same as the dot. One of the greatest features in modern printing is the ability to vary the dot or pixel size.
Using the popular 5 megapixel size of many low end scanners yields an image of about 8.5 by 6.5 inches from a 35mm negative when printed at 300dpi. This is its "natural size", the size the image will be if left unaltered and printed at 300dpi. This 5 megapixel rating is its hardware capability. The value is calculated by multiplying the width by the height of the resulting image. DPI is calculated, as the term implies, in dots per inch. The fact that the inch is not variable produces a standard. No software or other manipulation can change this hardware value due to it being a physical attribute of the hardware itself. Some scanners allow one to set the software resolution as high as 3600dpi causing the machine to do the same scan with software setting to a higher resolution. This gives a higher resolution at the image but not higher "quality" – nothing about the hardware has changed. This ability to apply software after hardware can be good if manipulation is intended. To scan any negative with enough quality to blow up and not down, today’s scanners need to start at about 1800 to 2400 dpi!
Much of today’s amateur work is web related making the small scanners a real bargain. Having a more versitile, higher quality scanner allows the user more options, as not all imagery is web bound. As stated, software can output any size file from the same hardware source but Quality is a function of hardware first. This is the first stop for your negatives.
Lets look at the popular 5 megapixel measurement. To convert that to comparable dpi one merely takes the square root of its megapixel rating. That gives a dpi of about 2200 for the 5 megapixel size. That’s the actual resolution of a 5 megapixel scan. A 3000dpi scan is 9 megapixels. A 4000 dpi scan is 16 megapixels.
Quality is determined by multiple factors starting with the hardware and ending with the consumer. These mathmatics are here to assist you in making your decision – to ferret out the manufacturer’s hype.

Use these calculators to compare any set of sizes to any other set of sizes.
megapixel

dimensions

dpi

raw size
in megabytes

300 dpi picture size

18.0

5077

x

3550

4245

42.5

16.9

x

11.8

20.6

5363

x

3750

4484

44.8

17.9

x

12.5

21.6

5563

x

3890

4652

46.5

18.5

x

13.0

23.7

5827

x

4075

4873

48.7

19.4

x

13.6

25.7

6063

x

4240

5070

50.7

20.2

x

14.1

27.9

6313

x

4415

5280

52.8

21.0

x

14.7

29.9

6535

x

4570

5465

54.6

21.8

x

15.2

31.9

6757

x

4725

5650

56.5

22.5

x

15.8

33.4

6907

x

4830

5776

57.8

23.0

x

16.1

35.8

7150

x

5000

5979

59.8

23.8

x

16.7

37.7

7343

x

5135

6141

61.4

24.5

x

17.1

38.8

7450

x

5210

6230

62.3

24.8

x

17.4

41.3

7685

x

5374

6426

64.3

25.6

x

17.9

44.4

7972

x

5575

6667

66.7

26.6

x

18.6

46.8

8180

x

5720

6840

68.4

27.3

x

19.1

49.1

8380

x

5860

7008

70.1

27.9

x

19.5

50.0

8458

x

5915

7073

70.7

28.2

x

19.7

50.6

8509

x

5950

7115

71.2

28.4

x

19.8

51.5

8580

x

6000

7175

71.7

28.6

x

20.0

51.8

8610

x

6021

7200

72.0

28.7

x

20.1

52.3

8652

x

6050

7235

72.3

28.8

x

20.2

