What extension tubes do.

[Vincent Azzano]

What extension tubes do.

Okay, this is my first photo how to thread in a while, so please bear with me.

Extension tubes are available in a variety of sizes for SLR cameras, there are 3rd party brands and there are ones made by the OEM, but they all have the same purpose, to reduce the minimum focus distance of a given lens. All of my examples are taken with the same camera, the same lens, and the same aperture, so that depth of field was not affected in that way. The camera is a 1D from Canon, the lens is a 70-200 2.8L with a minimum focus distance of 1.5m without any modifiers. Here is a sample of the absolute closest that I can get to my Milliapora without any modifiers:

Not to bad right? Wrong! Well, it is OK for an overall picture, it is in focus etc... but you can't really see any detail. How can you get closer? Well I could CROP the image in photoshop or lightroom, or any other of the many post processing programs that are available today. The biggest problem with cropping, is that you are reducing the percentage of pixels that are actually used on the subject. I know, that sounds weird, but think of it this way, if I were to crop that image in close, even though I used an 8MP camera to take the image, I may only be using 2-3MP on the cropped image. So what right? Nope. The fewer MP you have, the less detail you can keep. The best solution is to put more of the subject on the sensor. That is the advantage of the extension tubes, by reducing the minimum focus distance I can put more pixels on the subject. These next images were captured using increasingly more and more extension tubes. In order from least to most:

12mm Extension Tube

20mm Extension Tube

36mm Extension Tube

Okay, that is it for single tubes, how about stacking them? Yup!!! I can do that too!

48mm

56mm

68mm

So why wouldn't you use extension tubes all the time? Well there are some disadvantages to their use. One is the reduction in depth of field, you can see in these images how the background (and foreground) gets more and more out of focus as the length of extension tubes increases. Another disadvantage is that the longer the tube gets, the longer your shutter speeds need to be. Longer shutter speeds mean that you have to use a tripod, it also means that unless you are VERY good at panning, that you will not be using an extension tube for fish pictures.

Is there a way to get even closer? Yup! You can add a diopter to the front of the lens, this last image is captured with all 68mm of extension tubes, PLUS a 500D diopter on the front:

More on diopters later!

If you have questions about extension tubes, feel free to ask them in this thread.

Thanks for reading,
-Mike

This was really helpful!! Thanks for the info

 

[robbyg]

This is just my opinion, but if your getting into Macro photography it's probably better to get extension tubes unless you have loads of spare cash. As you have seen you can get pretty good pictures with extension tubes that cost around $100. Yes dedicated Macro lenses will give you a better picture but your looking at typically a $900+ expenditure. If you find yourself really getting into Macro Photography then you can buy a good 1:1 Macro lens at a later date.

 

[d.fast]

900$ is a pretty expensive lens!(Though this is very relative if you start checking middle- to high-end products in the photography world) if you want to try macro photography I would suggest another route. Use vintage lenses instead. I have bought a few macro lenses on local flea markets for 10-25$ each and cheap adapters are about 10-20$. This applies mainly to mirror less cameras, I have zero experience with DSLRs. You will have no auto focus and have to learn adjusting aperture and shutter speed manually. All good skills to learn anyway and auto focus is not very important for macro shots imo.

Here is a shot of a tube worm shot on an old Sigma mini-wide 28 mm macro lens I found for 6$. Perhaps a bit of a lucky find, ebay prices are higher but there are tonnes of lenses around for old film cameras that in general have no value yet for the average person unless they are really special lenses. For normal photography they might be a bit tough to use, but for macro shots of invertebrates they are a great starting point. Perhaps a rough start for a new photographer but you will learn quickly and it is very rewarding.

 

[Lovefish77]

Interesting topic - I think best of both worlds if you pair a macro lens with an extension tubes, in my understanding that is the only way you can go beyond 1:1 magnification. Any macro lens can only get you 1:1; beyond that you need to mount or stack extension tubes.

 

[d.fast]

No, that's not really true. Here is the secret with extension tubes:

They move the focus point so you can get closer to your subject and still focus. This is what's making the extension tubes able to turn regular lenses into macro lenses.

Macro is just a fancy term for lenses specialized for close focus.

We have another problem that most macro shooters don't face, our subjects are in an aquarium so we are limited by their position in relation to the glass walls. Do in my case my lenses are pressed against the aquarium. Adding tubes to my macro lenses does not make a difference because I can't get closer, I need greater magnification and the only way to do that is to get bigger lenses. Well there are some other methods, but they have flaws.

There are macro lenses that provide greater magnification than 1:1 as well, here is one example: https://petapixel.com/2020/08/18/venus-optics-unveils-the-worlds-first-2x-ultra-macro-lens-for-mft/