Week 4 : 11.2.2011 - Lens Choice, Performance & Testing

Week 4 : 11.2.2011 - Lens Choice, Performance & Testing

I used a Canon Ef 24-70mm f2.8 L USM Lens for the purpose of this tesing.






http://www.leedervillecameras.com.au/slr-lenses/canon/canon-ef-24-70mm-f2-8l-usm




I found it to be a reasonably consistant lens but it does feature some barrel distortions and slight vignetting. Below are the visual results of the lens test ranging from f2.8 through to f22 at two different focal lengths of 24mm and 70mm which is the extent of this lens range. This practical test gave me a better understanding as it allowed me to view this not just read about it. I consider myself a very visual learner and I really found a lot of benefit from this test.

I found that at its widest point of f2.8 there where some very noticeable barrel distortions particularly at 24mm focal length. There is a degree of light fallout at this same focal length and wide aperture but it seems to have dissapeared at f5.6 as well as when it is zoomed to 70mm.

This lens is generally used as a portrait lens and there for the distortions that are present shouldn't have as great as an affect that it would if shooting architecture. This lens appears to be at its sharpest at around f4/f5.6. I am looking to add a new lens to my kit and I know that there is similar research to this on the internet. I will now be able to interpret these online results better to find the perfect lenses for me.


f 2.8 @ 70mm



f4 @70mm


f 5.6 @ 70mm


f8 @70mm



f 11 @70mm



f16 @ 70mm

f 22 @ 70mm

f 22 @ 24 mm

f16 @ 24mm

f11 @ 24 mm

f8 @ 24mm

f5.6 @ 24mm

f4 @ 24mm

f2.8 @ 24mm

Week 3 : 4.3.2011 - Large Format Cameras & Camera Movements

Week 3 : 4.3.2011 - Large Format Cameras & Camera Movements

Image from: http://www.dannyburk.com/ebony_sv45u2.htm

Advantages:

- Better resolution for given print size

- Sheet film = control of processing

- Full control of composition, image shape, d.o.f, film back position, perspective

Disadvantages

- Heavier & nearly always requires a tripod

- Cumbersome and requires more preparation

Format Sizes

- 4x5

- 5x7

- 8x10

- 11x14

Types

- Monorail

- Flat-bed

- Press

- Field

Camera Movements

Image From Workshop 3 - Intro to Large Format Cameras Powerpoint

- Manipulation of ;

- focus

- Perspective

- D.O.F

- Image Shape

by the relative position and orientation of the lens board and film back.

Rise and Fall:

• Rise is an upward movement and fall is a downward movement control the vertical placement of the image on the ground glass.
• The rise and fall of the rear standard does not effect the shape of the subject, giving the option of moving the object within the frame without changing the position of objects relative to each other.
• The rise or fall of the front standard changes the point of view and to some extent the shape of the subject and visual relation of objects.

Shift:

• A sideways movement, is the same as the rise and fall of standards except the movement takes place from side to side. Spatial relationships change with a shift of the front standard and not the back standard.

Tilt:

• A forward or backward angled movement of either or both the standards, can change both the shape and the focus of the image on film.

Swing:

• an angled left or right movement of either the rear or front standards, can change the shape and/or focus of the image.

The ‘Scheimpflug’ Principle

Control of image sharpness depends on the directional relationship of three planes: the subject plane S, the film plane F and the lens plane L. As long as all three planes are parallel to each other, the image is uniformly sharp all over. See Figure 8 below. But when you incline one of the three planes to one of the others, you get uniform sharpness only when the extensions of all three planes intersect in a common point. This is known as the 'Scheimpflug Principle', the application of which has become known only in this department as "flugging" or "to flug it".

Week 2 : 25.2.2011 - Portable Lighting Revision

Week 2 : 25.2.2011 - Portable Lighting Revision

Flash and Monobloc Powerpoint

The history of the flash

- First flash - magnesium metal ground fine enough to make it burn rapidly to produce instant light.

- Next advancement contained flash

- Electronic flash built into camera : convenient fill light, low output can cast funny shadows

- Portable electronic flash : powered by batteries, typically high output

Image: http://www.the-digital-picture.com/reviews/canon-580ex-ii-speedlite-flash-review.aspx

- Monobloc : Powered by mains supply, high variable output

- Studio : Powered by mains supply, extremely expensive, very high variable output

- Flash power source : Powered by either mains power or by battery

- Flash duration is given as the time in milliseconds that it takes for the flash to 1/2 its peak value

- Inverse Square Law : double the distance away from the flash the subject will recieve 1/4 of the power

Workshop: Flash Self Portrait

Task: To take a self portrait using flash lighting and submit the RAW file. Photographs must be shot in manual and correctly exposed.

Photographed with a Canon 40D 50mm lens

f4 @1/160th of a second ISO 100

Lighting Set up:

The lighting setup was fairly simple. One speedlight was positioned on the front to the right to light the face (creating a few harsh shadows) and another behind to make it a little bit more interesting but mostly just because I seem to love lens flare. Another light or at least a reflector on the left side would have helped to fill in those shadows.

Digram Created at: www.lightingdiagrams.com