# 100mm L Macro: Extension Tubes vs Close Up lens for extra magnification?



## cayenne (Aug 18, 2016)

Hi All,

I just recently scored on the Canon 100mm L Macro lens and starting to get into the wonderful world of macro photography.

It is, I believe a 1:1 magnification lens. I'm in need of advice on how to get more magnification while keeping quality.

I've heard extension tubes are one way to do this. However, from my research, it seems to indicate that extension tubes are best done for shorter focal length lenses and that the benefits start to really dimmish as the focal length increases....I found (and lost) a weblink that showed what you get per mm focal length and the 100mm didn't seem to benefit that much. 

This article also said that the 100mm might benefit more from something called a Close Up lens, which seems basically to be a screw on magnifying glass. It said this had limits at some point with adding distortion at the edges I believe...?

So, hoping to get some advice...preferrable *Bang for the Buck* if at all possible...hahaha.......but get thoughts on the best route to go to go beyond 1:1 macro shooting with the 100mm Macro....

And in each category, what's the best to get on extension tube(s) and which is best to get for a Close Up lens for it?

Thank you all in advance!!

Cayenne


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## neuroanatomist (Aug 18, 2016)

Tubes vs. diopter lenses, an old debate. A close-up lens is an optic, therefore it affects IQ in a meaningful way. An extenstion tube is just air, so no meaningful optical decrement. From a practical standpoint, the optical hit on a good lens is minimal. I compared a Canon 500D on my 70-200/2.8L IS II with my bare 100L, and any differences in IQ were not readily apparent even viewing at 100%. Note that I mention the Canon 500D as it's the close-up lens of choice, there are other brands out there but Canon is considered the highest quality. 

IMO, 70-100mm is the gray zone where they derive some benefit from either approach. Longer than 100mm, the close-up lens is certainly the better way to go. Shorter than 70mm, tubes are better. In the case of the 100L, you're better off with extension tubes. 

For the close up lens, first off you'd need to adapt a larger close-up lens as there isn't a 67mm version (so you'd need a Canon 500D 72mm and a 67-72mm step up ring). You're correct that the 100L is a true 1x macro (1:1 reproduction). The approximate max magnification you'd get with a 500D close up lens is *1.28x*. With the non-L macro, you can go higher with the 250D close-up lens (1.44x), but that optic is only available up to 58mm threads, too small for the 100L. 

A 25mm extenstion tube on the 100L will get you to 1.37x, so already there's a benefit over the close up lens. Moreover, tubes can be stacked. Since your primary stated use is macro, I'd go with the Kenko tubes – you can get a set of three different sizes for less than just the Canon EF 25 II, and the air in the Canon tubes is no better (although I personally have the Canon tubes, I got them becuase my main use is a closer MFD with my 600/4 II and I trust the mount strength of the Canon tubes for the heavy gear, but that's not an issue with the 100L).


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## Random Orbits (Aug 18, 2016)

I know it's not one of the choices you offered, but MP-E 65. ;D


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## Mikehit (Aug 18, 2016)

Close-up lenses vary in price from a few dollars to over a hundred dollars. What you are paying for is better performance as you move away from the centre of the lens. The Canon lens (and the Nikon version if you can find it) have a double element to give better image quality hence th ehigher price. Cheap ones are a good way of seeing if you really want to get into photography greater than 1:1 and what you need to do to get there. 
With these lenses you keep the amount of light but lose quality

Extension tubes come with and without electrical connections (called 'auto' tubes) which maintain AF and metering and IMO it is worth the extra to get them with connections. With tubes, as Neuro mentions, it is only air so you maintain image quality but you start to lose light because you are pushing the macro lens further from the body. 

Having tried both (I bought the 58mm Canon close-up lens for my 70-300 zoom and later bought the Kenko tubes) I would say you get better bang for the buck with the tubes. But I take the close up lens with me for walkabout because it is easier to add and remove. 


In the last couple of years other makes of extension tube have appeared but make sure you look at ones with metal mounts.


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## cayenne (Aug 18, 2016)

Wow!!

Thank you both for the great replies!!

Ok, I'm gonna go the extension tube route to start with....

Can someone tell me the difference between these two sets of Kink extension tubes besides the price?

https://www.amazon.com/Kenko-Auto-Extension-Canon-Mount/dp/B000U8Y88M

And https://www.amazon.com/Kenko-Extension-Canon-Lenses--EXTUBEDG-C/dp/B000JGD9JY

They both appear to work with the Canon EOS camera...full frame....?


Thanks in advance,

cayenne


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## neuroanatomist (Aug 18, 2016)

Random Orbits said:


> I know it's not one of the choices you offered, but MP-E 65. ;D



Yes, that's my 'higher than 1x' option. Well, one of them. The MP-E takes TCs, too so it goes to 10x. After that, I mount my camera onto a Zeiss Stemi DV4 Stereomicroscope that delivers 20-80x magnification. ;D


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## neuroanatomist (Aug 18, 2016)

cayenne said:


> Can someone tell me the difference between these two sets of Kink extension tubes besides the price?



The difference appears to be just the $26. Since the cheaper one is actually sold by Adorama, that's the way to go.


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## cayenne (Aug 18, 2016)

neuroanatomist said:


> Random Orbits said:
> 
> 
> > I know it's not one of the choices you offered, but MP-E 65. ;D
> ...



Wow..as usual, you are full of fantastic information.
That lens is pretty cool looking.

May I ask..when doing focus stacking with that MP-E 65 lens...what do you use if not something like the RRS macro rails system?

Thank you in advance!!

C


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## kphoto99 (Aug 18, 2016)

One more option, Auto close-up reverse adapter:
http://www.tomtop.com/adapters-converters-301/p-d3631.html
It can work as a simple auto extension tube, but it is more flexible.
I got it a while ago, it is well made.


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## cayenne (Aug 18, 2016)

kphoto99 said:


> One more option, Auto close-up reverse adapter:
> http://www.tomtop.com/adapters-converters-301/p-d3631.html
> It can work as a simple auto extension tube, but it is more flexible.
> I got it a while ago, it is well made.



Oh thank you!!

that looks interesting indeed!! Does this work with any lens? What lenses/focal lengths work best for reversing the lens?


Thanks in advance,

cayenne


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## Mikehit (Aug 18, 2016)

cayenne said:


> kphoto99 said:
> 
> 
> > One more option, Auto close-up reverse adapter:
> ...



I have not seen those so cheap before (when I last looked a few years ago it was difficult to even find them!) Very interesting indeed

Yes, they will work with any lens but when reversing the traditional advice is to look at a lens 35mm or wider. 
If you think about it a wide angle lens takes a wide angle (obviously!) and squeezes the view into a narrower field. So if you reverse it, it takes a narrow section (the fly) and expands it to larger than life on the sensor.
All you need to do is find a way of connecting the filter ring on the lens to the mount on the body. 

Old-school is to buy a lens that has an aperture ring but this gizmo will work with auto lenses as well. Thanks, kphoto99.


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## danski0224 (Aug 18, 2016)

cayenne said:


> May I ask..when doing focus stacking with that MP-E 65 lens...what do you use if not something like the RRS macro rails system?
> 
> Thank you in advance!!
> 
> C



Given what they cost, those RRS macro rails are a huge disappointment to me.

There is a huge amount of slop in them, especially problematic when making back and forth adjustments. Something like the MP-E 65 just throws a huge spotlight on the problem. 

Henjar Photo has an extremely well made macro rail that is adjusted with a Mitutoyo micrometer. The price is relatively comparable and it's a much better product than the RRS macro rail.

And you can use extension tubes and a close up lens at the same time ;-)


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## Mt Spokane Photography (Aug 18, 2016)

cayenne said:


> kphoto99 said:
> 
> 
> > One more option, Auto close-up reverse adapter:
> ...



Reverse adapters are difficult to use. You must use a adapter ring to match the front lens thread. Zoom lenses work poorly, and with a 50mm lens, you must get very close.

Get the tubes, they are a much better solution for a 100L. I use reverse adapters to adapt unusual lenses because the camera mount does not matter. Focus is by moving camera and lens toward or away, so a macro rail is almost a necessity.

I can use AF with my 100L and a short tube, but a macro rail is best for high magnifications as well.

So, get tubes and a macro rail. They are the same story, cheap ones and expensive.


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## neuroanatomist (Aug 18, 2016)

cayenne said:


> May I ask..when doing focus stacking with that MP-E 65 lens...what do you use if not something like the RRS macro rails system?



Seems we're blending threads here  but Random Orbitz alluded to my solution. I do use the RRS rail for stacking, but I use Helicon Focus instead of PS for processing the stack.


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## kphoto99 (Aug 19, 2016)

Mikehit said:


> cayenne said:
> 
> 
> > kphoto99 said:
> ...



This comes with adapters for different filter thread sizes. It can also be connected together and used as a ~32mm extension tube.


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## tolusina (Aug 19, 2016)

The arithmetic to calculate the additional magnification provided by extension tubes is quite simple.

Start with a lens' native magnification from the lens' specification page.

Then divide the length of the extension tube(s) used by the lens' focal length, add the result to the lens' native magnification and you're done.

I'll give several examples, then calculate total magnification for each after adding the full 68mm stack of Kenko tubes.
- - -
Both 
EF 100mm f/2.8L Macro IS USM
and
EF 100mm f/2.8 Macro USM
have 1X magnification specs.
68mm ÷ 100mm = .68X additional magnification, 1.68X total with a full tube set.
- - -
EF 50mm f/2.5 Compact Macro also has 1X native magnification.
68mm ÷ 50mm = 1.36X additional, 2.36X total.
- - -
EF 40mm f/2.8 STM 
0.18X native
68mm ÷ 40mm = 1.7X additional, 1.88X total.
- - -
TS-E 24mm f/3.5L II
0.34X native
68mm ÷ 24mm = 2.833...
3.17333...X total
- - -
The longer a lens' focal length, the less additional magnification from the addition of extension tubes and the opposite. 
Notice that, with a full set of tubes, total magnification of the Shorty Forty is greater than the 100 Macros. I've no idea which combination is more suitable nor why one might be better than the other.

Depth of field gets incredibly thin, stacking is almost mandatory.

Lighting well at close distances is always a consideration.
- - -
I listed the TS-E 24mm primarily as an arithmetic example, I've no idea if tilt and or shift of the image circle can work together with extensions.
Someone here knows, I'm hoping they'll chime in.


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## neuroanatomist (Aug 19, 2016)

*TL;DR*

To determine magnification with an extension tube you need to use the effective focal length of the lens at the minimum focus distance, which is not the number printed on the barrel. You can get that value from Canon's information, but you have to go deeper than the top-line specs.
There's a practical limit to the length of extension tube(s) you can use – tubes shorten the working distance (front of lens to subject), as tube length gets longer the working distance gets shorter and eventually negative.




tolusina said:


> The arithmetic to calculate the additional magnification provided by extension tubes is quite simple.
> 
> Start with a lens' native magnification from the lens' specification page.
> 
> Then divide the length of the extension tube(s) used by the lens' focal length, add the result to the lens' native magnification and you're done.



Not quite done... Yes, the arithmetic is simple using the formula you describe:

*m' = m + (L/f)* where *m'* is the new max magnification (with tube), *m* is the specified max mag of the native lens, *L* is the length of the extension tube (or stack of tubes) and *f* is the focal length of the lens. (For Doug Kerr's derivation of the formula, go here.)

That formula works great...as long as you use the proper input values. But unfortunately, you're not. Also, it's worth noting that the arithmetic (even when done with correct values) doesn't tell the whole story.




tolusina said:


> I'll give several examples, then calculate total magnification for each after adding the full 68mm stack of Kenko tubes.
> - - -
> Both
> EF 100mm f/2.8L Macro IS USM
> ...



That seems simple, but unfortunately it's wrong. 

Let's use your example.
---
Both 
EF 100mm f/2.8L Macro IS USM
and
EF 100mm f/2.8 Macro USM
have 1X magnification specs.

Based on your simple arithmetic, with a 25mm extenstion tube
25mm ÷ 100mm = .25x additional magnification, *1.25x* total with the EF 25 II tube

But in their respective instruction manuals, Canon states that with the EF 25 II tube, the magnification will be *1.37x* for the 100mm L lens and *1.39x* for the 100mm non-L lens.

So, either Canon doesn't know how to determine the specifications for their own products, or there's something wrong with the way you're calculating the final magnification. I'll go out on a limb and say the Canon knows what they're doing. 

Now..._what_ is wrong with your calculation? The problem is that you're using the specified focal length of the lens, e.g. 100mm in the case above. Sure, it's printed on the barrel and all, but it's important to realize that the specified focal length is with the lens _focused at infinity_. When a lens is focused, a small group of elements within the lens actually moves to achieve focus. The consequence of that is that the focal length of the lens – which is properly defined as the distance from the sensor to the second/rear nodal point – changes as the lens is focused, because the position of the second nodal point moves as the lens is focused. Thus, the resulting effective focal length of a lens when focused at the minimum focus distance is shorter than the focal length at infinity. How much shorter depends on the design of the lens, e.g. what type of focusing system is used, where the focusing group sits in the optical path and how the focusing group moves (for a _crapload_ of detail on that sort of thing, see Pierre Toscani's information and animations here and here). 

I don't think many photographers are aware of this issue, which is commonly referred to as focus breathing. When you focus closer, the focal length gets shorter resulting in a wider FoV. For a still image with a subject at a 'normal' distance, it's likely that you wouldn't notice the effect at all. But in some cases, it can be quite significant. For example, if you're using a Nikon 70-200mm f/2.8 VR and take a tight close up at 200mm, you're essentially getting the framing of a 135mm lens. OTOH, videographers and cinemaphotographers are acutely aware of focus breathing, since it means that the framing/composition of the footage changes as you pull focus during a shot. One reason why cine lenses are so expensive is that they have minimal to no focus breathing. 

Although I suggested not many photographers are familiar with focus breathing, I expect many macro photographers are – anyone who's tried doing focus stacking by changing the focus of the lens (manually or with something like Helicon Remote and a tethered camera) will notice that the FoV changes through the stack. That's why the better way to focus stack is to move the whole camera+lens on a focus rail.

Ok, back to the example above where the formula-generated magnification doesn't match Canon's specifications. In the case of the 100mm f/2.8L Macro IS lens, which is 100mm at infinity focus, the _effective_ focal length with the lens focused at the minimum focus disance is ~68mm. So, back to the arithmetic:

25mm ÷ 68mm = .37x additional magnification, 1.37x total with the EF 25 II tube, and that matches Canon's value
68mm ÷ 68mm = 1x additional magnification, 2x total with the full Kenko tube set

Ok, but how do you determine the effective focal length at MFD for a given lens? It's not listed in the specs, and although there are a few 'focus breathing calculators' and formulae out there, they're not accurate becuase the effective focal length is dependent on the position of the rear nodal point within the lens, and that is in turn dependent on lens design. One way to determine the actual focal length is to empirically measure it, but without going into exhaustive details, I'll sum up by saying it's a royal PITA (it's pretty easy for distant objects, but the math breaks down at close distances, and that's what we really need to know). 

Fortunately, there is someone who knows how the lens is designed and knows exactly where the rear nodal point is at the MFD – the people who make the lens! If you look in the Canon instruction manual for most lenses, they provide value for the maximum magnification when used with the Canon EF 12 and EF 25 extension tubes. If you're using a single Canon tube, you're done – they've given you the maximum magnification. But if you're using Kenko tubes or stacking Canon tubes, you need to know the effective focal length at the MFD. You can estimate that with a rearrangement of the formula above and more simple arithmetic:

*fe = L ÷ (m' – m)*, where *fe* is the effective focal length at the MFD, *L* is the tube length associated with the Canon-provided maximum magnification *m'*, and *m* is the native magnification of the lens. You can get the *m'* values for the two Canon tubes in the instruction manuals for most lenses. 

For example, with the 180L Macro, the fe at 1:1 is 119mm. The effective focal length of the EF-S 60mm macro at 1:1 is 41mm.




tolusina said:


> EF 50mm f/2.5 Compact Macro also has 1X native magnification.
> 68mm ÷ 50mm = 1.36X additional, 2.36X total.



Actually, the 50mm Compact Macro is only 0.5x native magnification, unless you add the Life Size Converter (which costs nearly as much as the lens itself) to bring it to 1x mag. 




tolusina said:


> EF 40mm f/2.8 STM
> 0.18X native
> 68mm ÷ 40mm = 1.7X additional, 1.88X total.
> ---
> Notice that, with a full set of tubes, total magnification of the Shorty Forty is greater than the 100 Macros. I've no idea which combination is more suitable nor why one might be better than the other.



I'd say the 100mm macro would be a much better choice, because if you stack 68mm of extenstion tubes behind the 40/2.8 lens, the focus distance will be shorter than the resulting length of the optics, i.e. _the subject would need to be inside the lens_ in order to be in focus. This is one of those cases where calculating the theoretical maximum magnification gets dashed against the rocks of practical reality.




tolusina said:


> TS-E 24mm f/3.5L II
> 0.34X native
> 68mm ÷ 24mm = 2.833...
> 3.17333...X total
> ...



While the TS-E 24mm can work with tubes, including tilt and shift, this is another case of practical limitation. With a 12mm tube on the TS-E 24, you get 0.85x and the focus distance is about 3 cm in front of the lens. With a 25mm tube, you'll get a bit over 1x and the subject will need to be touching the front element (Canon doesn't recommend this, for obvious reasons). You certainly can't achieve focus with >25mm of tubes behind the lens.


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## chrysoberyl (Aug 19, 2016)

neuroanatomist said:


> Random Orbits said:
> 
> 
> > I know it's not one of the choices you offered, but MP-E 65. ;D
> ...



I can't find this Zeiss Stemi DV4 Stereomicroscope at Lensrentals...snicker.


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## Mt Spokane Photography (Aug 19, 2016)

I would not use tubes for a lens wider than 50mm because you must be very close to the subject, and even if that is not a issue, lighting something when the lens is 1/4 or 1/2 inch away can be a big issue. 

The 100L has enough working distance to let you light the subject evenly.


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## chrysoberyl (Aug 20, 2016)

Mt Spokane Photography said:


> I would not use tubes for a lens wider than 50mm because you must be very close to the subject, and even if that is not a issue, lighting something when the lens is 1/4 or 1/2 inch away can be a big issue.
> 
> The 100L has enough working distance to let you light the subject evenly.



I use a 20mm ET with my 100mm Milvus, and like it well (the working distance is fully acceptable), but it is a 1:2 macro. I have used the 500D close-up lens on my 100L and like the IQ, but the limited range is inconvenient.


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## cayenne (Aug 22, 2016)

danski0224 said:


> cayenne said:
> 
> 
> > May I ask..when doing focus stacking with that MP-E 65 lens...what do you use if not something like the RRS macro rails system?
> ...


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