# Anyone tried an extension tube with a big white to reduce min focus distance?



## GuyF (Sep 8, 2014)

Taking shots at the weekend from a bird hide with my 5D3 plus 500mm mk2 and quite a few times found the minimum focus distance was maybe just a couple of feet too far (I wasn't able to move further back). Flipping through a book by David Noton (Google him if you're not familiar with his work), he mentions having used a 14mm extension tube with a 500mm lens for the same reason. He doesn't say anything regarding losing a stop of light or what the min/max focus distances get reduced to so I wondered if any of you know how to calculate the changes in min/max focus based on an extension tube of size "x" with a lens of length "y".

If any of you have used a tube to reduce the min focus distance of a big white, I'd be grateful for any info you can offer.

Thanks!


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## Lawliet (Sep 8, 2014)

GuyF said:


> so I wondered if any of you know how to calculate the changes in min/max focus based on an extension tube of size "x" with a lens of length "y".



distance of subject to sensor = (focal length + width of the ring)*(1+(object size/image size on the sensor))
Keep in mind that in most modern lenses the actual focus length changes due to internal/rear focusing; you can use the formula w/o ring and the actual distance and magnification to get the real focal length at minimum distance


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## mackguyver (Sep 8, 2014)

GuyF said:


> Taking shots at the weekend from a bird hide with my 5D3 plus 500mm mk2 and quite a few times found the minimum focus distance was maybe just a couple of feet too far (I wasn't able to move further back). Flipping through a book by David Noton (Google him if you're not familiar with his work), he mentions having used a 14mm extension tube with a 500mm lens for the same reason. He doesn't say anything regarding losing a stop of light or what the min/max focus distances get reduced to so I wondered if any of you know how to calculate the changes in min/max focus based on an extension tube of size "x" with a lens of length "y".
> 
> If any of you have used a tube to reduce the min focus distance of a big white, I'd be grateful for any info you can offer.
> 
> Thanks!


Yes, I've used the 12mm and 25mm extension tubes for just that reason. Art Wolfe and Arthur Morris do this as well. According to TDP, you're magnification changes as follows:

Maximum Magnification (MM) 0.15x 
Magnification Range with 12mm Ext Tube 0.18-0.03x 
Magnification Range with 25mm Ext Tube 0.22-0.06x

In terms of the new MFD, you'll just have to sort that out, but you can probably find the numbers out there somewhere. You'll lose infinity focus, AF doesn't work well, if at all, and the closer you get, the more light you'll lose, but it's not a shocking amount. Wide open shots may have a bit more vignetting as well. To get closer, these trade offs are worth it, however.


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## 20Dave (Sep 8, 2014)

mackguyver said:


> ... You'll lose infinity focus, AF doesn't work well, if at all, and the closer you get, the more light you'll lose, but it's not a shocking amount. Wide open shots may have a bit more vignetting as well. To get closer, these trade offs are worth it, however.



Since I don't (yet) have a macro lens and I started shooting insects this year, I started using extension tubes quite a bit. I don't have the specific formulas that you are looking for, but I will say that losing infinity focus doesn't just mean "way out there". You may be surprised at how close "infinity" becomes. And, it got very annoying for me to keep taking the tube on and off. They do the job as advertised (shorten the focus distances), but it takes a little time to get used to. I most often used the long extension tube (25mm or longer), so using the 12mm probably won't have as dramatic of an effect. 

As for the AF, I found that I couldn't AF often because my subject wasn't in the new focus range. I end up usually trying manual focus first just to see if it is in range, then let the AF take over from there. I've never had an issue with AF once I knew that the subject was in the focusing range.

One last comment of something that I read about but still surprised me in practice - when I attached the extension tube to my 70-200 mm zoom, adjusting the zoom actually moves the focusing range rather than zooming in/out. That also took some time getting used to.


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## mackguyver (Sep 8, 2014)

Dave, using the tubes on the 70-200 is a bit different because you're wanting to use them for near-macro work. I believe Guy is wanting to get closer to subjects than his lens' roughly 12 foot minimum focus will allow. This is a problem with long lenses (particularly the 800mm which has a 20 foot MFD). If a small bird or something comes close, you want to get it framed or at least closer to it and the tubes let you do that. You are not going to get anywhere where near 1.00x (1:1), but it's nice to have for those types of shots when standing 8 feet instead of 12 feet away makes a big difference.


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## Skatol (Sep 8, 2014)

GuyF said:


> Taking shots at the weekend from a bird hide with my 5D3 plus 500mm mk2 and quite a few times found the minimum focus distance was maybe just a couple of feet too far (I wasn't able to move further back). Flipping through a book by David Noton (Google him if you're not familiar with his work), he mentions having used a 14mm extension tube with a 500mm lens for the same reason. He doesn't say anything regarding losing a stop of light or what the min/max focus distances get reduced to so I wondered if any of you know how to calculate the changes in min/max focus based on an extension tube of size "x" with a lens of length "y".
> 
> If any of you have used a tube to reduce the min focus distance of a big white, I'd be grateful for any info you can offer.
> 
> Thanks!


From another thread. I asked a similar question.

Quote from: neuroanatomist on August 20, 2014, 08:11:31 PM

Quote from: Skatol on August 20, 2014, 03:41:21 PM

Quote from: neuroanatomist on August 12, 2013, 11:57:46 AM

...(the only reason I went with Canon tubes is that my main use is to reduce the MFD of a supertele, and I wanted to be sure of the mount strength - not an issue of concern for macro lenses).

For starters math is not my strong point. Just curious as to how much the MFD is reduced on a 600mm lens when using extension tubes. I currently have two setups.
1. 300/2.8 w/ 2x TC, MFD ~ 10ft.
2. 600/4(non-IS), MFD ~ 20ft.
Will an extension tube(s) get my 600 MFD to ~10 ft?
My slight understanding of the math says no.
Thanks for any enlightenment you may provide.


*An EF 25 tube will get your 600/4 to an MFD of ~15 feet.*


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## 20Dave (Sep 8, 2014)

mackguyver said:


> Dave, using the tubes on the 70-200 is a bit different because you're wanting to use them for near-macro work. I believe Guy is wanting to get closer to subjects than his lens' roughly 12 foot minimum focus will allow. This is a problem with long lenses (particularly the 800mm which has a 20 foot MFD). If a small bird or something comes close, you want to get it framed or at least closer to it and the tubes let you do that. You are not going to get anywhere where near 1.00x (1:1), but it's nice to have for those types of shots when standing 8 feet instead of 12 feet away makes a big difference.



Agreed, I wasn't clear in my post as to when I was answering his question or just giving some additional information. Originally, I was using the tubes for the same reason - my 400mm f/5.6 also has a very long MinFD, and often I couldn't get that far back without standing in a lake or off the trail in the trees. It was just after using the tubes for a bit that I started using it for more macro work. 

Not coincidentally, I am going to pay close attention to the MFD of the new telephoto lens coming out (or was going to when I thought that it was a 100-400). If it can improve on my 400mm, then I would consider upgrading. I just wish that there was one lens that could handle the work for both the short MFD that I'd like for insects and the long reach for birds. The 300mm 2.8 seems closest to fitting the bill, but it's not quite long enough for birding (and it ain't cheap).

Thanks,
Dave


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## Steve (Sep 8, 2014)

I've used extension tubes on my Sigma 300-800 because it has a long 6 meter MFD. It's....weird. It definitely lets me focus closer but it mucks up the zoom bizarrely. I can keep infinity and focus closer at 800mm, which is great, but focus is completely out of whack all through the rest of the zoom range and barely works at all by 300mm. 

At any rate, this is pretty niche info here since I'm in the distinct minority as an owner of this lens but I thought I'd throw that out there to any lurkers who might have one and be curious about how well it takes tubes.


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## Mt Spokane Photography (Sep 8, 2014)

After discovering the MFD of my 400mm f/5.6L, I researched the mfd and magnification for various Canon telephoto lenses before buying one to use for closer distances. Those with a reasonably long focal length, IS, and good magnification are the 300mm f/4 L(59.1", 0.24X Magnification) 100-300mm L (47.2" 0.21X Magnification)and 100-400mm L (70.9", 0.20X Magnification) They are good for getting close shot of small birds. A TC on the 300mm f/4 will get even more magnification without changing the mfd. (No Canon TC's fit the 100-300L, and a TC on the 100-400L requires f/8 AF ability.) 

Since its difficult to get a small bird to hold still when you move closer or further away, I bought the 100-400L so I can zoom. I certainly hope that any replacement keeps the magnification in the 0.2 or greater range.

The new Sigma 150-600 has a 0.2 magnification and a 8.5 mfd which is good for a 600mm lens. The Tamron 150-600 has nearly the same specs.


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## Lurker (Sep 8, 2014)

http://www.bobatkins.com/photography/eosfaq/closeup.htm

Down the page a bit is a table. Don't think it has the new lenses, not sure if that's an issue or not.


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## scyrene (Sep 8, 2014)

I tried a 12mm tube with the 500 II but the maximum focus distance was surprisingly close, and I found getting accurate focus a lot harder. No doubt practice will help  Also be aware that cheaper tubes may not be strong enough to support the lens - I had one shear through, albeit with a couple of extenders added. Handle with care!


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## DominoDude (Sep 8, 2014)

Steve said:


> I've used extension tubes on my Sigma 300-800 because it has a long 6 meter MFD. It's....weird. It definitely lets me focus closer but it mucks up the zoom bizarrely. I can keep infinity and focus closer at 800mm, which is great, but focus is completely out of whack all through the rest of the zoom range and barely works at all by 300mm.
> 
> At any rate, this is pretty niche info here since I'm in the distinct minority as an owner of this lens but I thought I'd throw that out there to any lurkers who might have one and be curious about how well it takes tubes.



Super! This information is golden.


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## jvhigbee (Sep 9, 2014)

I have recently been using 2 12mm tubes and a EF 1.4 lll extender on my EF 70-200 f2.8L IS ll and it reduces the mfd to about 30". I really like what I've been getting. When the sun comes back out later this week I will try it on my 300mm.
http://www.pbase.com/jvhigbee/pad


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## Jack Douglas (Sep 9, 2014)

Here's Downy with 300 and 36 mm ext. No cropping. Set-up from a blind, maybe 5 feet. Not sure if I really needed the tube for this shot but I had been in closer. Data is included in the shot. Everything is automatic and focus is fast.

I love the 300 with and without tubes for butterflies - near macro at a distance.

Jack


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## GuyF (Sep 9, 2014)

Many thanks to all of you for giving me your thoughts and experience. I've always said this site is excellent for the quick and useful advice from (most of) those who use it.

I'll do a bit more research - I see Kenko tubes appear quite similar to Canon in that they use metal where it matters.

I'm lucky to also have the 300mm f2.8 mk1 but couldn't carry it and the 500mm around at the same time, hence thoughts of extension tubes. (Why have one mid-life crisis when you can have two and buy a big white each time to cheer yourself up? )

As a small thank you, have a slightly over-saturated shot of a Nuthatch taken with the 300mm (I'm not really a bird watcher but am told the Nuthatch is very rare this far north in the UK. There's bleedin' loads in my local woods).

Take care.


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## Steve (Sep 9, 2014)

GuyF said:


> I'll do a bit more research - I see Kenko tubes appear quite similar to Canon in that they use metal where it matters



Brand doesn't really matter with extension tubes since there's no optics. Metal is probably better and you definitely want the pass through contacts. I've got cheap Opteka's and they're fine. They fit snug and are perfectly solid. I don't think I'd trust a full stack of them to hold the weight of my 300-800 but on a tripod its no worries.


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## Jack Douglas (Sep 9, 2014)

Just to mention that my set is Kenko and I don't allow them to carry the weight of a lens or use multi-stack with the 300 or 300 X2 (too much play). Was a great deal on Amazon last year so about $150 for the set (about 1/2 local store price), no regrets.

Another uncropped, ISO 1600 dull day. 300 with 36 ext. DOF is a real challenge.

Jack


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## neuroanatomist (Sep 9, 2014)

GuyF said:


> I'll do a bit more research - I see Kenko tubes appear quite similar to Canon in that they use metal where it matters.



Personally, I feel more comfortable with the Canon-branded tubes between my 600 II and my 1D X, that's a fair bit of weight even on the back end.

I bought my Canon tubes used, got the two of them for less than the Kenko set, and the fact that there's no optics means low risk with a used purchase.


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## scyrene (Sep 9, 2014)

Steve said:


> GuyF said:
> 
> 
> > I'll do a bit more research - I see Kenko tubes appear quite similar to Canon in that they use metal where it matters
> ...



Internally, the Kenko tubes are plastic. I had one shear through when mounted to a large lens/teleconverter combination. The screws in the metal mount are fitted into plastic underneath. I've heard that Canon tubes are stronger inside, but I have no firsthand evidence of that.


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