Eleven Questions

1. What are the limitations of a focal plane shutter?

• Distortion of fast moving objects with slow shutter speeds
• Slow flash synch speeds
• Noise
• Camera shake
• Life expectancy

2. Should a between the lens of leaf shutter be cocked during lens
attachment/removal?

The Hasselblad 500 c/m manual says it should be cocked.

3. What is the max speed of a BTL shutter?

Normally about 1/500

4. What is the definition of depth of field?

‘The nearest and furthest parts of a subject which can be rendered sharp at a given
focus setting.’ – The Photographers Handbook – John Hedgecoe

5. How is depth of field increased?

Reduce the aperture or decrease the focal length of the lens.

6. Why is the automatic diaphragm fully open until the shutter release is pressed?

To allow maximum light through to the viewfinder.

7. What are the two types of sensor arrays? And briefly describe the differences
between the two types.

CCD – charge coupled device
CMOS – Complimentary metal oxide semi-conductor

A CCD is an analogue device and transfers each pixel’s charge sequentially to a
common output structure, which converts the charge to a voltage.
In a CMOS the charge-to-voltage conversion takes place in each pixel. (CCD Vs
CMOS – Facts and Fiction – Dave Litwiller)

8. What does a photosite record?

a) colour
b) a level of light
c) grey tones
d) all of the above

I'd say D if you include the Bayer filter.

9. What is interpolation?

Interpolation is used when making an image larger or smaller. A mathematical
formula calculates what the missing pixel information should be by sampling the
pixels nearby.

10. Explain step by step the process of RAW file capture.

• An exposure is made
• Light is captured by each photosite on the sensor
• The intensity of the light is recorded at the sensors bit depth
• Each photosite is covered by a colour filter array (Bayer – green-red-green-blue)
• Photon->electron->voltage->digitized

11. What is the difference between jpeg and RAW files?

A RAW file is the information that the sensor has captured. It has only red, blue or
green pixels, as it has not been through demosaicing. It allows greater flexibility in
the development of an image.
A JPEG is a compressed file format (8 bit) that has been demosaiced, white balance
applied and other changes. It could be done in camera or by software such as
Photoshop/Lightroom.