I gave a talk to the Marlborough Camera Club on 11 May 2006, using a PowerPoint presentation. The text on the slides appears below. Click here, or on any one of the titles, to view the complete slides, including images.

1. Resolution in Photography

An Introduction

 

 

Harry R. Matthews
2006

2. Resolution means:

•      Sharpness

–  or, more precisely:

•      “Smallest object you can distinguish”

•      “Amount of information.”

 

3. Resolution

•      Depends both on the
display
device

•      And on the image

 

4. Resolution of common display devices

•      This projector resolves
1024 pixels horizontally and 768 pixels vertically

•      A computer screen typically has
70 to 100 pixels per inch

•      A high resolution photographic print
resolves 300 pixels per inch
e.g. a 12"x8" print has 3,600 x 2,400 pixels

•      A sharp 35 mm slide has several thousand pixels per inch.

 

 

5. Final resolution

•      Depends on either
the underlying
resolution in your file
or
the display resolution,
whichever is less.

 

6. What resolution do you need?

•      High resolution (large file)

–   Cropping and other computer manipulation

–   Sharp prints

•      Low resolution (small file)

–   Images suitable for emailing or the Web

–   Number of images in your camera

–   Number of images on your computer

–   Number of images on a CD or DVD for archiving or distribution

–   Hiding defects like noise, graininess, soft focus.

 

7. Example of the same image presented with different resolutions

 

8. Blow up high resolution example

 

9. Blow up medium resolution example

 

10.                 Blow up low resolution

 

11.                 For the same resolution:
Different file types give different file sizes

 

12.                 How to control the resolution in your image – the camera

•      Adjust your camera resolution to its highest practical setting

•      Recommended file type in camera:
     RAW + JPEG or
     largest, highest quality, JPEG

•      Disadvantage is less images per card

–  buy a larger card.

13.                 How to control the resolution in your image – the computer

•      Use your image editing program on the RAW file, if you have it

•      First, re-save your image as a TIFF or PSD and keep the original as well

•      Edit the image and save it before changing the resolution or file type

•      Save the image at the resolution you want, probably as a JPEG file.

14.                 Image – Resize – Image size

15.                 Image Size dialog box/a>

16.                 Image resize example
1845 x 1646

17.                 Print size

18.                 Reduced to print at 6″ x 4″

19.                 Resized to 1345 x 1200

20.                 Sized to fit this projector

21.                 Sized to fit the screen

22.                 For email:
File – Save for Web …

23.                 Save for Web dialog

24.                 JPEG quality

25.                 Image size

26.                 Email size

27.                 Why does resolution vary
between images?

•      Lens quality and cleanliness

•      Camera quality
(e.g. focal plane, mirror shake …)

•      Film or sensor size
(e.g. APS, 35 mm, medium format etc. film or
5 Mpixel, 8 Mpixel, 16 Mpixel etc. for digital)

•      Film speed (graininess) or ISO rating (noise)
…

28.                 Why does resolution vary
between images?

•      …

•      Camera motion (shake)

•      Subject motion (motion blur)

•      Correct exposure

•      Focus

•      Contrast in the subject.

29.                 Factors affecting resolution

30.                 Measuring resolution
Option 1

•      Pixels per inch (dots per inch)

•      E.g.

–  300 dpi for printing

–  72 dpi for screen (or email)

–  4000 dpi for a 35 mm slide

•      Potential maximum resolution is 1/300 inch or 1/72 inch or 1/4000 inch.

31.                 Measuring resolution
Option 2

•      Pixels per inch

•      Image size

–   total number of pixels in your image

•      E.g.

–   1 million for a cell ‘phone

–   2 to 8 million for a “point-and-shoot” digital camera

–   6 to 16 million for a digital SLR

•      My EOS 350D

–   image size is 3456 x 2304 = 8 million pixels

–   horizontal resolution is 1/3456.

32.                 Measuring resolution
Option 3

•      Pixels per inch

•      Image size

–  total number of pixels in your image

–  or, file size for an uncompressed 8-bit TIFF file L.

33.                 Web address for this presentation