Week 11 - 11 Questions

1. What is the maximum lens aperture?
How wide the diaphragm opens.

2. If a 50mm lens has an aperture diameter of 25mm what f stop is it set at?
Focal length/ aperture diameter = 2

3. What is a lens aberration? And why do they exist?
Problems with the lens. No lens is perfect and have some compromises.

4. What is spherical aberration? How can it be reduced?
Where light passing through the centre of the lens has a different focal point to that traversing the edge. It can be reduced by stopping down the lens.

5. What are chromatic aberrations?
Light of different colours is not focused at the same point. Causes colour fringes.

6. What do these lenses do?

a) achromatic – lens corrected for two different wavelengths

b) apochromatic – lens corrected for three different wavelengths

c) superachromatic – lens corrected for four different wavelengths

7. What is coma?
Cannot produce a sharp point away from the lens axis – looks like a comet

8. What is astigmatism?
An inability to focus sharply horizontal and vertical lines near the edge of the sensor/film

9. What is distortion? And geometric distortion?
A lens being in front of or behind the aperture causes barrel or pincushion distortion. Geometric distortion covers both of these.

10. What is curvature of field?
A lens that cannot produce a flat image of a flat subject.

11. What is a sweet spot on your lens?
Where the lens performs at its best for sharpness.

First folio photos...

The first person I've started photographing is Danny. He works at the local tip but also runs the Bungendore music and poetry evenings. The contrast between what he does as a job and what his true passions are is what I'm documenting.

 

 

The photos above are all of Danny at work.

Danny has been involved with music all of his life and is an accomplished guitar player. Once a month he runs the music and poetry evenings in Bungendore. He has been doing this for the last seventeen years!

I had a few technical issues taking the photos at the venue. I had to push my camera to its maximum ISO (3200) so the photos were very noisy. Also, I had to shoot at 1/40th at f4. I've converted them to black and whit to try and hide some of the noise.

 Danny's mate - they were playing together

Week 7 - 15 Questions

Light and Lenses

1. The speed of light is medium dependant. Which means it changes speed depending on what it
is travelling through. Does it get slower or faster travelling through denser mediums. Yes or
no?

It travels slower and can be calculated by the refractive index of a material. Glass is about 1.5
so the speed light travels is c/1.5

2. If light enters glass at an angle other than 90 degrees what happens to it? Explain.

It bends due to refraction. As light slows entering glass it changes direction. At 90 degrees it
is still refracted but does not change direction.

3. Light travels in waves. What is the measurement for this?

Wavelength – visible light is within the range of 350-790 nm

4. What is the degree of the refraction of light dependant on? And which colour is refracted the
most?

The degree of refraction is dependant on the refractive medium and its wavelength. Violet is
refracted the most.

5. What is the angle of incidence?

The angle at which a light ray approaches a medium.

6. What is the refractive index of material?

A number that is used to calculate the speed that light traverses a medium. Glass is about 1.5
so the speed light is traversing it is c/1.5

7. What is the difference between a convergent and divergent lens?

In a convergent lens the light rays are bent inwards and cross at the focal point. In a divergent
lens the light rays are bent outwards.

8. What is the focal length of an optical system?

The distance from the front of the first lens through to the focal point.

9. What are circles of confusion?

A lens that is focused on an object does not render everything sharp. Depth of field will show
some things as sharp and some things as blurred. The circle of confusion are those parts of the
image that are no longer sharp as perceived by the human eye or the largest blur spot that the
human eye would still see as a point.

10. What is the angle of view of a lens?

The angle of the scene that the lens will include in an image.

11. What is the covering power of a lens?

The usable area of the image circle a lens makes.

12. Do lenses alter perspective?

Yes – long lenses shorten perspective and wide angle increase perspective.

13. What is geometric distortion?

When lines appear to be bent. Common forms are barrel distortion or pincushion distortion.

14. What is the equation to calculate correct viewing distance?
And, PROBLEM to solve:
You need to make a vertical portrait using 24x36mm format which will be used on a roadside billboard
where the photo will be 5m high and it will be ideally seen from 50m. What lens focal length should
you use to maintain ‘correct’ seen perspective?
Given: image height = 36mm
print height = 5000mm (5m)
viewing distance (VD) = 50,000mm (50m)
Unknown: magnification (M) = print / image
= 5000 / 36 = 139x
focal length (f) = ?

15. For the following lens types, write a description of each
using no more than 10 words for each lens.

Wide angle – field of view greater than what a human eye sees

Zoom – a lens with variable focal lengths

Long focus – focal length greater than the diagonal of the sensor

Telephoto – lens is shorter than the focal length

Retro focus – regular focal length with wide angle attachment

Quasi fish eye – image covers the entire sensor

Fish eye – field of vie greater than 100 degrees

Catadioptric - mirror used to increase focal length but maintain small overall length

Macro - produces images sizes greater than 1:1

Teleconverter – increases focal length of lens with a 1 stop drop normally

Supplementary or close up lens – accessory attached to front of lens to alter focal length

PC or tilt shift lens – perspective correction lens

Assignment 2 - Proposal for folio

The proposal I have for my folio is based on Elliott Erwitts’ view ‘that you
should always let people be themselves.’ Elliott was probably talking about
photographers placing their subjects exactly as the photographer wanted
them within, possibly, a contrived scene and that this may not be the best way
to photograph them. Several of his photographs show well-known people in a
completely different light. An example of this is the photo he took of Countess
Wolf-Stomersee – an aging Sicilian aristocrat in financial decline. He was able
to show that the world sees her as a Countess but really she was an aging
lady with a large financial debt and a decaying home.

However, this idea made me think that people who have a professional career
and have an image that they portray to the wider community may not be
showing their true identities. Quite often the lives that people live outside of
their profession may be a truer insight into the personality of that person.

I plan on taking pictures of people performing their professional duties in their
place of employment. By contrast I will take pictures of them doing what their
passions dictate in their private lives. If possible (and where appropriate) I will
try and take some pictures of the person undertaking what they really like to
do dressed in their professional attire e.g. a stone mason in his work clothes
drawing a picture.

Examples I have in mind are:

1. My local butcher – as well as running a successful butcher’s shop he is
also heavily involved with sheep dog trials on a national level

2. An air traffic controller – this person works shift work but still finds the
time to commit to his fly fishing passion

3. The stone mason – this person has the skills necessary to collect rock
and fashion it into buildings and walls but performs regularly in a band
and creates beautiful charcoal drawings

4. The waste disposal manager – he looks after the local tip by day but is
well known for his music and poetry

I think that a portfolio of this nature would be able to clearly demonstrate the
diversity of these people’s interests and be able to show their real passions. I
will also be able to show my own passion.

As well as being interesting, I think that this portfolio will add to my skills as a
photographer.

It will require me to negotiate with a variety of people with potentially diverse
backgrounds and obtain their consent to photograph them. In addition I think
that the subject matter will be challenging in the variety of conditions I will
need to photograph them in. This will include indoor locations, such as a
butcher’s shop, outdoor locations and also possibly night locations. Lighting
will be varied including daylight, tungsten and maybe some flash.

I believe that this portfolio would meet the requirements of the documentary
folio assignment.

Assignment 1 - Inspiration

One of the photographers that inspire me is Elliot Erwitt. As well as being a photojournalist he
was also well known in advertising and architecture. When he was working he always tried to
get a personal photograph as well - he called these anti-photographs.

 Kitchen Debate - Elliott Erwitt -
http://iconicphotos.wordpress.com/2009/04/24/kitchen-debate/

Elliot Erwitt -
http://www.silberstudios.tv/blog/2011/08/photographer-elliott-erwitt-showcases-favorite-images-innew-
nyc-exhibit/

Jackie Kennedy - Elliott Erwitt -
http://www.johnclearygallery.com/Elliott_Erwitt/elliott_erwitt_arlington_kennedy_photo.php


Erwitt also believed in 'letting people be themselves'. This is the basis for the idea I have for my
portfolio. I plan on taking pictures of people in their normal day to day job - how the world sees them with their public persona's. In contrast to this I will also take pictures of people doing what their passions tell them to do - how they spend their time away from their professional careers.

Week 6 - 10 Questions

1. Does size matter with sensor arrays?

Yes, but bigger is not always better.

a. An APS-C sensor uses more of the centre of the lens which
normally has the better optics
b. Smaller lenses can use smaller and lighter lenses
c. Larger sensors normally have less noise as the pixels are larger
d. Larger sensors have a shallower depth of field
e. Crop factor can also influence lens choice e.g. a 1.5 crop factor
sensor using a 50mm lens would be the equivalent of a 72 mm lens
on a full frame sensor.
f. The viewfinder is normally larger and brighter on a full frame sensor
g. Larger pixels normally have a higher dynamic range

2. What size, in millimetres, is a full frame sensor?

36mm x 24 mm

3. What does ‘crop factor’ mean when talking about sensor arrays?

It is the sensors diagonal size compared to a 35mm full frame sensor e.g.
you have to multiply an APS-C sensor by 1.5 to equal a full frame
sensor.

4. If crop factor is the longest side of full frame dimension divided by the
smaller sensor dimension, then what would be the crop factor if the full
frame dimension is 36mm and the small sensor dimension is 23.6 mm?

1.5

5. Is resolution lower or higher with large photosites compared to small
photosites?

It is higher with large photosites as diffraction occurs at smaller
apertures.

6. What is digital noise?

It is the signal to noise ration that occurs on a photosite and appears
similar to grain in film. Small sensors normally have higher noise as
well as higher ISO.

7. What is blooming of photosites?

This happens when a photosite has reached its maximum charge and
photons spill over over into other photosites. This appears as
overexposure.

8. Define dynamic range in relation to sensors.

The level of shadow detail and highlights a camera can record. It can
also be defined as ‘The dynamic range of a sensor is defined by the
largest possible signal divided by the smallest possible signal it can
generate.’ – (Vincent Bockaert)

9. Does the human eye have a better or worse dynamic range than your
camera?

Better – it can see over a dynamic range of about 24 f-stops.

10. What is bit depth?

The number of bits that are used to determine colour (or shades of
grey) e.g. a bit depth of 1 will only have two values as opposed to 8 bits
which have 256 values. 16 bits has a possible 64K values.

Hyperfocal distance – the near limit of depth of field for a given aperture when
the lens is set to infinity. It can also be described as the focus distance which
places the maximum allowable circle of confusion at infinity. It is normally set
by putting the infinity mark on the relevant depth of field scale for the aperture
that is in use. However, people like Harold Merklinger argue that the circle of
confusion used to determine depth of field scales is too large for modern day
films and sensors.

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.