extension tubes - a waste of time?

[philmar]

I am interested in doing some macro work - something to do around the house on these long cold winter evenings! I purchased a Kenko Extension Tube Set (12, 20 & 36mm Tubes) many months ago on the cheap but haven't gotten around to using them. Obviously they reduce the amount of available light (yes I have a tripod). And it seems the autofocus won't work. I haven't really bothered to read up on macro photography or extension tubes so I am hoping for a few words of wisdom/tips from anyone here.
I have Canon 24-70 L, 10-22 EFS and a 70-100 L IS. Do the tubes lend themselves to be better used with one (or none!!) of these lenses? Should I just not bother with tubes because they aren't useful (and why)?
I know nothing about macro photography. Would I have been better off investing in a good macro lens?
They look like a rather cheap (inexpensive) way to delve in to macro photography. I imagine they must have drawbacks over macro lenses (why else would people pay big bucks for them?).
So what are your thoughts on using extension tubes for macro photography? THANKS!


...oh, and when the weather gets better, just how DO you get them insect critters to hold still while you menacingly move that enormous (to them) 24-70 lens in their face?

[Digitally_Altered]

cant get any cheaper than what you have to work with, play away... I have used my 70-200 with extension tubes, but yes you will do well with a 100 2.8 macro

[John_B]

philmar,
They should work well with either your 24-70L or 70-200L

I personally would rather use a true macro lens like my 100mm f/2.8 for macro photos, as I can get better photos much easier with it.

However you can get true macro 1:1 with your current setup. I suggest you put all of the Kenko tubes on your 24-70L and set your lens to 70mm with AF off (or your 70-200L at 70 with AF off). This should give you true 1:1 life size macro. You can focus by moving the camera closer or further away from the subject. Using a flash (probably need an off shoe cord with external flash) will give you faster shutter speeds with more DOF (smaller aperture).

Good Luck with it :)

[philmar]

would the 100 2.8 macro work well with a crop sensor camera? - I have the 30D

[philmar]

philmar,
I suggest you put all of the Kenko tubes on your 24-70L and set your lens to 70mm with AF off (or your 70-200L at 70 with AF off). This should give you true 1:1 life size macro. You can focus by moving the camera closer or further away from the subject.

why not use the focusing ring to focus?

[John_B]

would the 100 2.8 macro work well with a crop sensor camera? - I have the 30DIt has worked well on my 40D ;)
why not use the focusing ring to focus?Because there is very little difference. ex. a Canon 28-105 f/3.5-4.5 lens set at 50mm can focus from 1ft to infinity normally however with 68mm of Kenko extension tubes it can focus from approximately 1/4" to 1/2" <-- a 1/2" from lens to subject when lens is set to Infinity ;)

[Mike]

I have only extension tubes for macro stuff - no macro lens. I use a Pentax 50mm f/1.7 lens with a manual aperture ring converted and mounted to some cheapo £5 tubes. The setup works very well for me and I can get some excellent results. In fact, one of my shots with this set-up has just been voted as a Maxshot for the Still-life share of the POTN Book Vol3.

As John says above using the focus ring is pretty pointless. As the depth of field is quite narrow just a slight forward or backward movement is all that is necessary for achieving your desired focus.

Getting good shots of critters is not at all easy - they move about quite a bit and it can get rather frustrating but the end results can be quite worthwhile.

Just as an example, here's a shot made with my pentax lens/tubes setup on my 30D:

http://photography-on-the.net/forum/attachment.php?attachmentid=256690&stc=1&d=1206474307

[Coppatop85]

I have some questions to!

I am in the same boat as the OP (check lenses). Why use the 70-200 at 70mm and not 200? What is the difference? Don't you get more working distance at 200mm?

I tried to use the tubes with a 50mm 1.8 a while back, but i found I had to get SO CLOSE to my subjects, I would either block the light, or scare the bug away. Especially while on a tripod, I have this big setup and it is hard to move it around slightly without scaring bugs off.

Also, how do reversing rings work. Is it possible to setup my sigma 30mm 1.4 reversed to my 70-200? What kind of reverser do I need? Would any of my other lenses work better reversed (tamron 17-50 maybe?)

Also, I usually find that no matter what aperture I use, the amount of space that is actually in focus is EXTREMELY small. Is this normal, or am I just working with the wrong equipment. If this is normal, how the hell do you shoot macro handheld (if at all)?

[John_B]

Coppatop85,
I suggest next time start your own topic with your questions ;)

Using the 70-200 at 70mm with a full set of Kenko extension tubes will give you just about true macro 1:1 Life size. If you set the lens to 200mm you will not get a macro photo, but a close up photo. :)

The simple math is extension used / Focal length used = Magnification

So in the case of a full set of Kenko extension tubes 68mm / 200mm focal length = mag of .34 or 1:3 which is 1/3rd of true macro

Being close to subject is a side effect of macro ;) That is why true macro lenses in the 180mm are made to give that extra few mm of room. The smaller the lens focal length the closer the subject has to be. ex. with a Canon 100mm f/2.8 macro lens the subject is about 6" away from the glass when set at 1:1 macro

You can reverse a lens onto another lens but working distance between lens and subject is very very small!

Small DOF is a reality in macro photography that is why many use small apertures f/16 or smaller or combine many photos.

Using a flash makes hand held macro photography much more possible :)

[Coppatop85]

Thanks John!

[marcoj70]

Hey John, how did you come up with those calculations? At 100mm (with a 100-400 lenses on a 40D body) with the 3 Kenko rings I actually measured a magnification on 1.3 at minimum focal point, while at 400mm I had a magnification of around .9.
Back to Phil, I like the longer lenses for field work, where as you say the critters get spooked, because I can stay a little further away; I prefer a little less magnification than taking a picture of where a critter had been! (without the critter in the frame).
This is how I work:
I choose the lens to use in a specific situation knowing the lens min and max focusing distance with the 3 rings. For example, my 100-400 with 3 rings can focus between 15 cm at 100mm to approx 2.5 meters at 400mm (distance from the tip of the lens). So on field I first set the tripod at a distance within these borders. If the critter hasn't been spooked by this, I attach the camera to the tripod. If the critter hasn't been spooked even by this, I zoom the lenses to acquire rough focus, keeping the focusing ring at mid range. Then I fine tune the focus with the focusing ring. If by then the the critter is still there, and if I remembered to attach the remote, I finally take the picture!

To get a "table" of my lenses focusing distances for small distances, I used a simple ruler with a sliding mark on it, positioned it on a table with the tip at the edge of the table (or slightly over the edge). I mounted the lens on a tripod and positioned its lower side so it almost touched the edge of the ruler. I manual focused/zoomed to the desired combination, and then moved the sliding mark until it came to focus. Then I looked at the ruler.
For settings which have bigger distances I just try to "foot focus" (moving the camera) until it comes to focus on a picture on the wall, then estimate the distance.
Regarding magnification, I take the same ruler and set it parallel to the sensor plane and vertical or horizontal in the frame, then move the tripod with the camera until I achieve focus (by now I know what the distance should be ;) ). Then I count the millimeters (or inches fractions) I can see. A little math knowing the sensor size gives me the actual magnification for that settings.

[LordV]

Marco - not sure what sensor size you are using but with 68mm of extension tubes you should get about 0.7:1 at 100mm and 0.17:1 at 400mm. There may be some error in the calcs if the lens has significant magnification without tubes at min focus but it wouldn't be that much ?
Brian V

[John_B]

marcoj70,
Well I don't know how you got your numbers? ???
Here is a link that is great for figuring out the exact number Julian's Lens Calculator <-- click to see (http://eosdoc.com/jlcalc/)

For the math you truly get 0.17:1 at 400mm with 68mm extension tubes as (LordV said) when your lens is focused at infinity. When you lens is focused at its closest point I believe it is no longer 400mm in length and thus give different magnifications with extension tubes. The math isn't simple because many zoom lenses have internal focus which affects the numbers a bit too much to bother with for me ;)

However on a 40D with a 100-400L set at 400mm with 68mm of extension tubes with the lens set at its closest focus point you will not get 0.9:1 magnification. The magnification I got was 0.49:1 the photo showed 45mm of a ruler on a 22.2mm sensor.

Try again shooting a ruler in focus, then divide the size of the sensor (40D is 22.2mm) by the mm shown in the photo 22.2mm/45mm = 0.49 or about 1/2 life size ;)

Wow that was a macro mouthful :lol:

[philmar]

Thanks for the replies thus far....I'll digest'em tonight.

[philmar]

One thing I've noticed about some macros is the limited depth of field. This makes spot-on focus quite difficult. What are the advantages of a macro lens over extension tubes? is one advantage better DOF?

[LordV]

Philmar. The DOF in macro is unfortunately purely dependent on the aperture and magnification but not on how you achieve the magnification so the DOF at the same magnification and aperture would be the same.

Main advantages of a macro lens over non macro lens with ext tubes are.
#1 Still have infinity focus
#2 focus field is flatter edge to edge
#3 Focus distances are often longer at the same magnification.

It is quite common to use ext tubes with a macro lens to push the max magnification even further.
Brian V.