Equipment selection exercise.

'Butterfly Shoot'

Objective: to photograph butterflies of wing span say 30 to 70mm let us assume in each case an area of 30mm and 70mm side resp'

Chip sizes available

5D - 36 x 24mm 12.5Mpix (122pix/mm)

40D - 22 x 14mm 10Mpix (175pix/mm)

mag = image size / object size =

using 5D
24/70 = 0.343x
24/30 = 0.8x

using 40D
14/70 = 0.2x
14/30 = 0.467x

From above we need a range of: 0.343x - 0.8x or 0.2x - 0.467x

Which lens to use? or do I actually need to buy a 180mm Macro?

Assume using existing EF 70-200 ƒ2.8

 

 

Lens - Subject distance

Magnification
Zoom @200mm
1.4m
0.17x
Extenders    
1.4x
1.4m
0.24x max
2x
1.4m
0.36x max
Ext Tube    
12mm    
70mm
555mm - 624mm
0.22x - 0.17x
200mm
1110mm-3401mm
0.24x - 0.06x
24mm    
70mm
402mm - 407mm
0.41x - 0.38x
200mm
929mm - 1737mm
0.32x - 0.14x
500D Close up lens    
70mm

500mm max

0.21 - 0.14x
200mm
500mm max
0.55 - 0.39x

 

My choice is to use the EF70-200mm lens, 500D Close Up lens and take both backs

The only problem is where are the Butterflies? they are particularly rare this year (2008)

NB

1. The 180mm ƒ/3.5L Macro L-S distance 480mm at 1x

2. Despite 40D sensor being smaller it has a greater density 175px/mm as compared with the 5D's 122px/mm so at @100% pixel for pixel repro it is equivalent to a 19.6 x 30.8mm sensor at the 5D density