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Extension tubes - calculating the closest focus distance
I want to reduce the minimum focus distance of my Canon 70-300mm zoom for some close-up insect work (bees, butterflies, dragonflies etc).
I have a Canon 60mm macro lens but I find I have to get too close to the subject to fill the frame with this focal length which is obviously not ideal. I also have a Canon 500D close-up lens which is a pretty good performer but I'm thinking about buying an extension tube to retain the optical quality of the 70-300mm lens.
The Canon MkII extension tube is the obvious choice (rather than an independent make) because it works with EF-S lenses and I have a couple of those.
Now to the question, any idea how I work out the new closest focus distance, or focus range, when using an extension tube? I was looking to by the 12 OR 25mm rather than both (£69 & £109 each on a well-know retailer's site, probably a bit cheaper if I shop around).
I've had a trawl on the net but not found anything yet...
__________________ Stuart R
Life is an incurable disease with a 100% mortality rate
Re: Extension tubes - calculating the closest focus distance
Quote:
Originally Posted by StuartR
I want to reduce the minimum focus distance of my Canon 70-300mm zoom for some close-up insect work (bees, butterflies, dragonflies etc).
I have a Canon 60mm macro lens but I find I have to get too close to the subject to fill the frame with this focal length which is obviously not ideal. I also have a Canon 500D close-up lens which is a pretty good performer but I'm thinking about buying an extension tube to retain the optical quality of the 70-300mm lens.
The Canon MkII extension tube is the obvious choice (rather than an independent make) because it works with EF-S lenses and I have a couple of those.
Now to the question, any idea how I work out the new closest focus distance, or focus range, when using an extension tube? I wasy less looking to by the 12 OR 25mm rather than both (£69 & £109 each on a well-know retailer's site, probably a bit cheaper if I shop around).
I've had a trawl on the net but not found anything yet...
I don't know the formula for calculating the min focus distance, but I can tell you Jessops have their own brand which will support the auto features on your Canon camera and the set of three will cost lees than a single Canon unit.
Re: Extension tubes - calculating the closest focus distance
Quote:
Originally Posted by Patrick
I don't know the formula for calculating the min focus distance, but I can tell you Jessops have their own brand which will support the auto features on your Canon camera and the set of three will cost lees than a single Canon unit.
Patrick
I had a look at those Patrick but I'm fairly sure they don't work with EF-S lenses - I'll be proved wrong though!
__________________ Stuart R
Life is an incurable disease with a 100% mortality rate
Re: Extension tubes - calculating the closest focus distance
Quote:
Originally Posted by coupekid
Hi Stuart,
I have the Jessops ones, and they dont seem to autofocus with the standard kit lense if thats any help.
Not sure where you live Stuart, but if your in or around the Reading area, your more than welcome to try them!
Thanks for the offer coupekid but I took the plunge and bought a set from Jessops (much to my surprise my local store was open on a Sunday AND had them in stock - just the one set but then that's all I wanted . The latest version works fine with EF-S lenses (there's a note to this effect in the box). I've only taken a few test shots so far - hope to have something worth posting soon!
__________________ Stuart R
Life is an incurable disease with a 100% mortality rate
Re: Extension tubes - calculating the closest focus distance
Quote:
Originally Posted by carman
My experience of extension tubes is that the DOF is so small that auto focus is a waste of time. I got rid of my Auto Macro for just this reason.
I've already found it easier to switch the AF off most of the time when using the tubes but there have been a couple of occasions when the AF worked OK (bright conditions, using a single tube).
__________________ Stuart R
Life is an incurable disease with a 100% mortality rate
Re: Extension tubes - calculating the closest focus distance
Quote:
Originally Posted by carman
My experience of extension tubes is that the DOF is so small that auto focus is a waste of time. I got rid of my Auto Macro for just this reason.
I agree Manual Focus for macro is best and would always advise switching AF off, for several reasons not least that because of the limited depth of field, with manual you can select the best spot to focus easily to maximise what DF is available.
But auto tubes are still useful as the lens and camera can communicate other very helpful information such as exposure, shutter speed, and aperture and show them in the view finder.
Re: Extension tubes - calculating the closest focus distance
I now use an OM 50mm f.18 manual with OM-4/3 adapter on my E330. Using Live view mode B makes life so much simpler. I bought a set of manual tubes from Hong Kong the set up works fine.
__________________
The older I get the better I used to be!
. The latest version works fine with EF-S lenses (there's a note to this effect in the box). I've only taken a few test shots so far - hope to have something worth posting soon!
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