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2. Lens & Stabilisation - Sharpness Testing
  to identify certain problems encountered when using ‘very long zoom’ lenses.
(Test procedure devised by and article © Adrian Harris)

Test Method when Handholding Camera:
       Handholding tests show the effectiveness of stabilisation on image sharpness.

1. Set lens to max zoom and wide open = fastest aperture.
   (IE. Lowest f number. Example: f2.8, not f8. As using a small aperture such as f8 could hide any lens sharpness faults and would also slow down the test shutter speed).
2. Ensure shutter speed = minimum of 2 x equivalent FF focal length.
   (On M43, 400mm = 800mm FF = 1/1600th. The faster the shutter speed used for the test the better, but stay within reasonable ISO limits to prevent a poor image.)
3. Set camera to smallest focus square or point, and take careful aim at target letter.
   (This will help prevent focus errors).
4. Stand firmly, brace your arms against chest, hold breath, aim carefully at the target point and fire off a short burst of shots.
   (I use a series of 4 to 6 photos* to ensure I get at least one good image in case of camera user error!)
5. Test 1: Turn OFF all stabilisation (eliminates a possible problem source), take sequence of at least 6 photos.
6. Test 2: Turn ON stabilisation and repeat the shots.
   (If available try different stabilisation options).
7. Test 3: Repeat tests using a different camera or lens if available, to compare.

Test Method when Camera on Tripod : (A suitably rigid tripod is essential.)
        Manufacturers advise switching stabilisation OFF when using a tripod.

1. Prepare camera as in 1 - 3 above.
   (Using a 2sec timer delay or a remote shutter control will allow better images from slower shutter speeds if desired.)
2. No need for a long burst when using a tripod.
   (...but it is always wise to take a couple of shots just in case of user error.)
3. Do Test 1 and Test 3 as described above.

Examine and compare all images from each test sequence:

• Are they sharp - all over?
• Are the Stabilised shots sharp in different random areas?
  (a misaligned lens or over worked stabilisation can cause uneven sharpness)
• Note which sequence produced the highest rate of sharp shots.

Important Notes:

• When handheld shooting, park so that you can use the car to steady your camera.
• If testing a suspect zoom lens, repeat above test at different focal lengths.
• To ensure the camera focus is EXACTLY the same when inverted, it may be best to use fully manual focus control – but take care NOT to knock the focus control ring !
• * EXIF data does not indicate whether stabilisation is On or Off, so if you do this test and are also comparing how stabilisation versus no stabilisation affects sharpness, ensure you make note of the number of shots taken for each sequence!     

Article © Adrian Harris