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Test: Kenko extension tubes with Canon 100mm Macro
I finally got my set of extension tubes and did some testing, which left me with some questions. I'll try to explain what I did and what I don't get... I hope that somebody knows this stuff :-)
Let me start with the gear used and the test I did:
- Canon 7D body
- Canon EF 100mm F2.8L IS USM Macro
- Kenko extension tube set: 12mm + 20mm + 36mm
I put the camera on a tripod and shot the "peanut man face" on a tin with Planters peanuts. I tried every combination of tubes, measured minimum distance to subject and compare photo's.
The distance measured is between subject and the bigger contact of the hot shoe. I think it's close to the distance from sensor but it's the differences that are more important.
Okay, first shot, this is the 100mm without extension tube(s):
Here, the minimum distance is 29.7cm (and maximum is infinity)
#2 with 12mm tube:
minimum distance: 29.7cm
#3 with 20mm tube:
minimum distance: 30.0cm
#4 with 12mm + 20mm = 32mm tube:
minimum distance: 30.5cm
#5 with 36mm tube:
minimum distance 30.8cm
#6 with 36mm + 12mm = 48mm:
minimum distance 32.0cm
#7 with 36mm + 20mm = 56mm:
minimum distance 32.5cm
#8 with 36mm + 20mm + 12mm = 68mm:
minimum distance 32.8cm (maximum distance 40.8cm !!)
#6 and #7 make no sense to me. I realize that there's a jump in the minimum distance to subject and with the sensor further away we loose ground, but why is there this jump? And why is #8 so much closer again?
With all tubes mounted, there's only 8cm possible distance variation for the full focus range.
The 100L is 1:1 magnification and with all three tubes it looks like I get 2:1 magnification. There are formula's to calculate this... who can explain them?
I have a 1.4x teleconverter on the way too and heard this 100mm is compatible with it?!
thanks,
Nick.
Let me start with the gear used and the test I did:
- Canon 7D body
- Canon EF 100mm F2.8L IS USM Macro
- Kenko extension tube set: 12mm + 20mm + 36mm
I put the camera on a tripod and shot the "peanut man face" on a tin with Planters peanuts. I tried every combination of tubes, measured minimum distance to subject and compare photo's.
The distance measured is between subject and the bigger contact of the hot shoe. I think it's close to the distance from sensor but it's the differences that are more important.
Okay, first shot, this is the 100mm without extension tube(s):
Here, the minimum distance is 29.7cm (and maximum is infinity)
#2 with 12mm tube:
minimum distance: 29.7cm
#3 with 20mm tube:
minimum distance: 30.0cm
#4 with 12mm + 20mm = 32mm tube:
minimum distance: 30.5cm
#5 with 36mm tube:
minimum distance 30.8cm
#6 with 36mm + 12mm = 48mm:
minimum distance 32.0cm
#7 with 36mm + 20mm = 56mm:
minimum distance 32.5cm
#8 with 36mm + 20mm + 12mm = 68mm:
minimum distance 32.8cm (maximum distance 40.8cm !!)
#6 and #7 make no sense to me. I realize that there's a jump in the minimum distance to subject and with the sensor further away we loose ground, but why is there this jump? And why is #8 so much closer again?
With all tubes mounted, there's only 8cm possible distance variation for the full focus range.
The 100L is 1:1 magnification and with all three tubes it looks like I get 2:1 magnification. There are formula's to calculate this... who can explain them?
I have a 1.4x teleconverter on the way too and heard this 100mm is compatible with it?!
thanks,
Nick.
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Comments
Where the sensor end of the rig is takes care of itself - but having an appreciation of the 'air gap' is useful in several ways.
pp
Flickr
Yes; that "gap", or better, the differences of it while changing tubes, is known because you just take the length of the added tubes and subtract that from my measurement.
What is troubling me is why #6 and #7 give me less magnification instead of more
ciao!
Nick.
Nick.
my equipment: Canon 5D2, 7D, full list here
my Smugmug site: here
Figures below are: extension / subject width on frame / min working distance (didn't bother with max wd)
(working distance being from front of lens barrel to subject - distance from subject to sensor plane for lens only being 304mm)
Set cam + target up on a flat board
Cam on live view (x10), moved subject (steel rule taped to a vhs cassette
rinse, repeat.
More than willing to concede that results aren't 'dead on' ... as all done by mk1 eyeball, as was going out with (different) gear (dying rays from yellow orb still present)
... but they're in the right ball park ... and seem reasonable / as expected?
100mm only ... 28mm ... 110mm
+12... 24..... 100
+20... 22..... 94
+32... 19.4... 88
+36... 18.8... 86
+48... 16.8... 81
+56... 15.9... 78.5
+68... 14.3... 75
pp
Flickr
tnx,
Nick.
Nick.
my equipment: Canon 5D2, 7D, full list here
my Smugmug site: here
The real world size of the subject as represented across the frame / image.
ie for the lens without tubes, the image depicts 28mm's worth of rule markings - roughly as expected because the cam's sensor is 28.7mm wide.
With a full set of tubes, the frame's depicting 14.3mm's worth of rule, therefore magnification is 28.7/14.3 ... or approx 2:1 / twice life size.
hth
pp
Flickr
got it; I thought you used this ruler to measure distance to lens
I'll repeat this with my 7D and "new" 100mm.
I also have a 5D Mk.II on the way and will test with that too!
thanks,
Nick.
Nick.
my equipment: Canon 5D2, 7D, full list here
my Smugmug site: here
When using such items, I tended to think in terms of the subject size and to what extent I wanted it to fill the frame - and use the appropriate rings / kit.
pp
Edit
Just noticed you also have a 70-200.
If you haven't already done so, I'd suggest trying this with the extn tubes also.
Before I had any 'proper' macro lenses I used to use a 100-300 f5.6L with tubes ... and found it quite useful in certain situations.
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