grebeman
Old Codgers Group
- Name
- Barrie
Yesterday, for my pains, I was given some homework by Streetshooter (Don) to describe in some detail the combinations of extension tubes that I had been using with a Kern Paillard Yvar 150mm, f/4 C mount lens I was kindly given some weeks ago.
I'm sure you all know, but for the sake of completeness extension tubes fit between the lens and the camera mount. Since this lens is an old fashioned 1950's manual focus/manual stop down lens the tubes are just that, simple tubes. There are 3 in total with lengths of 10mm, 20mm and 40mm. Using simple mathematics (the principle of addition) the lengths of extension possible are 10mm, 20mm, 30mm (10+20), 40mm, 50mm (10+40), 60mm (20+40) and 70mm (10+20+40).
Just what does this mean in practice?
The first thing is that as you move the lens further away from the sensor plane in the camera the light has to travel further and so less light will reach the sensor. Given our modern all singing, all dancing cameras the exposure adjustment necessary to cater for this will be made automatically by the camera. Phew, one less thing to think about.
Secondly as you move the lens further from the sensor plane with the tubes the lens will focus at closer distances than it would without the tubes, and it wil no longer focus on infinity. So how much by you ask?
The figures below are, in order left to right, extension tube length, minimum focus distance, maximum focus distance and approximate horizontal field of view
none, 13 feet, infinity
10mm, 58in (1470mm), 87in (2210mm), 11in (280mm)
20mm, 35in (890mm), 46in (1170mm), 4in (100mm)
30mm, 27in (685mm), 33in (840mm), 2.6in (65mm)
40mm, 21.5in (550mm), 25in (635mm), 2.25in (60mm)
50mm, 18.75in (475mm), 20.5in (520mm), 2in (50mm)
60mm, 17in (430mm), 18in (460mm), 1.6in (40mm)
70mm, 15in (380mm), 15.75in (400mm), 1.25in (32mm)
These figures are all approximations.
The 20mm extension is probably the best for butterflies and dragonflies, for damselflies perhaps 30mm or 40mm (non to experiment with now) and small flies 60mm or 70mm. Full flowers 10mm or 20mm depending on the size of the bloom with close detail using the 70mm.
I have used the lens fitted with extension tubes up to 60mm handheld, although it's perhaps best at 10mm or 20mm when it is possible to focus without using the magnified focus assist. Your experience of this might vary dependant on the accuracy of the dioptre setting in your viewfinder and your own eyesight. Above 20mm the magnified focus assist is essential (built into m4/3 cameras, no experience of others) since the depth of field is very limited. The camera is best focused by moving it backwards and forwards slightly, hence the use of a focusing rack visible in the photograph below.
Note that when used without extension tubes this lens produces some vignetting of the corners of the image, so m4/3 sensors are the limit of sensor size for these C mount lens (16mm movie lenses).
The following series of photographs illustrates the change in the field of view as the length of the extension tubes is increased. The Honeysuckle flower is approximately 2.375in (60mm) across and the bug in some later shots is approx 0.33in (8mm) long
10mm extension tube, 72in (1830mm) from front of lens to subject, f/4
20mm extension tube, 36in (920mm) from front of lens to subject, f/5.6
30mm extension tube, 27in (690mm) from front of lens to subject, f/8
40mm extension tube, 22in (560mm) from front of lens to subject, f/11
50mm extension tube, 18in (460mm) from front of lens to subject, f/11
60mm extension tube, 17in (430mm) from front of lens to subject, f/11
70mm extension tube, 15in (380mm) from front of lens to subject, f/11
I must apologise for seemingly missing the point of focus in a couple of the above shots, but hopefully they illustrate the point.
Hope the above info is of interest to some of you.
Barrie
I'm sure you all know, but for the sake of completeness extension tubes fit between the lens and the camera mount. Since this lens is an old fashioned 1950's manual focus/manual stop down lens the tubes are just that, simple tubes. There are 3 in total with lengths of 10mm, 20mm and 40mm. Using simple mathematics (the principle of addition) the lengths of extension possible are 10mm, 20mm, 30mm (10+20), 40mm, 50mm (10+40), 60mm (20+40) and 70mm (10+20+40).
Just what does this mean in practice?
The first thing is that as you move the lens further away from the sensor plane in the camera the light has to travel further and so less light will reach the sensor. Given our modern all singing, all dancing cameras the exposure adjustment necessary to cater for this will be made automatically by the camera. Phew, one less thing to think about.
Secondly as you move the lens further from the sensor plane with the tubes the lens will focus at closer distances than it would without the tubes, and it wil no longer focus on infinity. So how much by you ask?
The figures below are, in order left to right, extension tube length, minimum focus distance, maximum focus distance and approximate horizontal field of view
none, 13 feet, infinity
10mm, 58in (1470mm), 87in (2210mm), 11in (280mm)
20mm, 35in (890mm), 46in (1170mm), 4in (100mm)
30mm, 27in (685mm), 33in (840mm), 2.6in (65mm)
40mm, 21.5in (550mm), 25in (635mm), 2.25in (60mm)
50mm, 18.75in (475mm), 20.5in (520mm), 2in (50mm)
60mm, 17in (430mm), 18in (460mm), 1.6in (40mm)
70mm, 15in (380mm), 15.75in (400mm), 1.25in (32mm)
These figures are all approximations.
The 20mm extension is probably the best for butterflies and dragonflies, for damselflies perhaps 30mm or 40mm (non to experiment with now) and small flies 60mm or 70mm. Full flowers 10mm or 20mm depending on the size of the bloom with close detail using the 70mm.
I have used the lens fitted with extension tubes up to 60mm handheld, although it's perhaps best at 10mm or 20mm when it is possible to focus without using the magnified focus assist. Your experience of this might vary dependant on the accuracy of the dioptre setting in your viewfinder and your own eyesight. Above 20mm the magnified focus assist is essential (built into m4/3 cameras, no experience of others) since the depth of field is very limited. The camera is best focused by moving it backwards and forwards slightly, hence the use of a focusing rack visible in the photograph below.
Note that when used without extension tubes this lens produces some vignetting of the corners of the image, so m4/3 sensors are the limit of sensor size for these C mount lens (16mm movie lenses).
The following series of photographs illustrates the change in the field of view as the length of the extension tubes is increased. The Honeysuckle flower is approximately 2.375in (60mm) across and the bug in some later shots is approx 0.33in (8mm) long
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10mm extension tube, 72in (1830mm) from front of lens to subject, f/4
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20mm extension tube, 36in (920mm) from front of lens to subject, f/5.6
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30mm extension tube, 27in (690mm) from front of lens to subject, f/8
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40mm extension tube, 22in (560mm) from front of lens to subject, f/11
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50mm extension tube, 18in (460mm) from front of lens to subject, f/11
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60mm extension tube, 17in (430mm) from front of lens to subject, f/11
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70mm extension tube, 15in (380mm) from front of lens to subject, f/11
I must apologise for seemingly missing the point of focus in a couple of the above shots, but hopefully they illustrate the point.
Hope the above info is of interest to some of you.
Barrie