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Archive 2017 · canon 100mm f/2.8 non-L macro

  
 
beanpkk
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p.1 #1 · p.1 #1 · canon 100mm f/2.8 non-L macro


I got these images using a 5Diii with the venerable Canon 100mm f/2.8 non-L macro lens. The question I have is about focus breathing. To wit.....

Here is the dandelion with lens focused at the front of the dandelion at pretty close to MFD:
CX0A1036 by K Knight, on Flickr

...and without moving the camera, here is the same dandelion with the lens focused at the back of the dandelion, call it MFD + 1.5 inches:
CX0A1064 by K Knight, on Flickr

Note the large difference in field of view, with the closer-focused image having a significantly smaller FOV than one focused just over an inch farther away. Does FOV equate mathematically to focal length? What does this large FOV difference say about the extent of focus breathing for that lens?

And here's the stack, which is fine within the field of view at closer focus.
dand4_stack by K Knight, on Flickr

With the Canon 100mm f/2.8 macro non-L lens, and with a subject the depth of a dandelion at MFD, using a rail, which I also did, creates a significantly smaller change in FOV than refocusing the lens. Given that ~any~ change in FOV is detrimental for focus stacking (where ideally you'd like no change in FOV at all), the rail should produce slightly better results. If the lens didn't focus breathe, the best option would be to refocus the lens rather than use a rail. I suppose a lens that will do 1:1 images at MFD w/out any change of FOV while focusing would be prohibitively expensive. But it would be fun to use!

I welcome any comments and discussion!

keith



May 29, 2017 at 09:37 AM
Ian.Dobinson
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p.1 #2 · p.1 #2 · canon 100mm f/2.8 non-L macro


do you mean the 100 2.8 macro NON USM ? or the newer USM (non L)

as for focus breathing . its not unusal . as you get closer to the subject most lenses loose some focal length . if you look at the specs the MFD of the 100 / 2.8 Macro is .31m (from the sensor) its the same for both the non USM and the USM

that equates to a focal length of 78mm

100mm 1:1 would actually be 400mm focus distance ..

interestingly the newer USM has the same MFD but doesn't extend as you focus closer , but the newest 100L has a slightly shorter MFD (.3cm) which means its a tad shorter again)



May 29, 2017 at 11:12 AM
Photonadave
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p.1 #3 · p.1 #3 · canon 100mm f/2.8 non-L macro


I suggest cross posting this in the Macro World forum.

Disclaimer: I have no experience in macro stacking so please filter what I say.

I would try useg the method that minimizes cropping of the final image or, to take things further, experimenting with using a combination of the two with the hope that the process would not be too much of a PIA.

I would search further as there's likely information on this topic out there depending on the wording used in the search box.

I had the USM non "L" version in the past and I'm sure it has focus breathing due to focal length as you are noticing. I suspect that most modern macro lenses and zoom lenses with a "Macro" feature are this way so that they either extend in length less or conversely to maintain ample clearance between the subject and the front of the lens.

I'm looking forward to following this post and learning from it.



May 29, 2017 at 01:03 PM
beanpkk
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p.1 #4 · p.1 #4 · canon 100mm f/2.8 non-L macro


Thanks Ian and Photonadave.

Ian: I'm using the old 100mm 2.8 USM non-L....I confess I didn't know Canon made a 100mm/2.8 macro w/out USM. How do you get from focus distance of 31cm to a 78mm focal length, or 100mm 1:1 to 400mm focal length? I'm confused about the numbers: if the angle of view shrinks dramatically as I focus closer, and if angle of view equates to focal length (smaller is longer), then the effective focal length of this lens goes ~up~ at MFD and not down. There must be something invalid about calculating focal length from AOV?

Photonadave: You can't know much less about this than I do! I'm no optics scholar that's for sure. I have found equations online that let me calculate focal length from angle of view, and if I measure the AOV at MFD I end up with a longer focal length, not a shorter one. I hadn't thought about the macro forum, since it's really an optics question but that's probably a good idea. I have been told that using a rail is necessary, and that simply refocusing the lens creates "a mess", but within the area of the smallest field of view, either method works. And refocusing is easier than digging out the rail and setting it up! I too am hoping that this thread will shine a light onto all of this.

Thanks,
keith



May 29, 2017 at 02:50 PM
pjbishop
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p.1 #5 · p.1 #5 · canon 100mm f/2.8 non-L macro


I appreciate your post. Focus-statcking is a topic of never-ending interest. There are what looks like some pretty useful DIY rail setups available and I plan on trying a couple.. As for the original non-IS, non-L 100 Macro, I wish I hadn't sold it and gotten the newer one. The copy I have is not as easy to focus and not as sharp as its predecessor. I had problems with it on the 5D Mark II and now also on the IV. ( It's already been in to Canon once, may have to try again ).

I used the older 100 Macro to photograph paintings, and it was very sharp and effective. I haven't done any of that lately, so don't know how the IS version will work in that regard.



May 29, 2017 at 03:52 PM
molson
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p.1 #6 · p.1 #6 · canon 100mm f/2.8 non-L macro


beanpkk wrote:
I suppose a lens that will do 1:1 images at MFD w/out any change of FOV while focusing would be prohibitively expensive.



Actually, it would be your cheapest option - the old pre-USM EF 100mm f2.8 macro can be had pretty cheaply these days (I just sold mine for $275) and it is just as sharp as the newer versions.

The "focus breathing" you are seeing is a common trait of internally-focusing lenses, which must change focal length in order to focus closer, the old lens focuses by extension which greatly reduces the focus breathing.

Edited on May 29, 2017 at 04:53 PM · View previous versions



May 29, 2017 at 04:52 PM
Ian.Dobinson
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p.1 #7 · p.1 #7 · canon 100mm f/2.8 non-L macro


beanpkk wrote:
Thanks Ian and Photonadave.

Ian: I'm using the old 100mm 2.8 USM non-L....I confess I didn't know Canon made a 100mm/2.8 macro w/out USM. How do you get from focus distance of 31cm to a 78mm focal length, or 100mm 1:1 to 400mm focal length? I'm confused about the numbers: if the angle of view shrinks dramatically as I focus closer, and if angle of view equates to focal length (smaller is longer), then the effective focal length of this lens goes ~up~ at MFD and not down. There must be something invalid about calculating focal length from AOV?

Photonadave:
...Show more

Keith , I'm using an online macro calc (Cambridge in colour) . It has a handy couple of tools that can show what a lens actual focal length is at mfd (some lenses loose a lot ) . But I have to confess that without knowing mag ratios at longer than mfd it's impossible to tell what focal lengths are . I presume that some lenses get closer to their quoted focal length earlier than others .

As for using a rail to stack I will say I've never really used one but it would seem to me that the one thing you don't want to do is change the focus on the lens .
Surely you set the rail up and focus at the farthest point needed and then pull backwards . Let's say the lens is at your mfd of .31m . Moving the rig back on the rail just moves the point of focus .31m backwards . So each image taken has a different point in focus but they were all .31m




May 29, 2017 at 04:52 PM
beanpkk
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p.1 #8 · p.1 #8 · canon 100mm f/2.8 non-L macro


Thanks, Ian. I'll check out that site.

I did do some experiments with the dandelion. I did some using a rail, and some just re-focusing. I did some front to back and some back to front. In terms of end result, I had trouble seeing any difference. For this subject, at MFD with a depth of about 1.5 inches, using a rail and moving the camera changes the field of view less than refocusing the lens because of the large amount of breathing this lens does. So the rail is probably the technically better option. For front to back vs back to front, I would tend to think that back to front would be better, but with this subject where the in-focus front covers up the back parts, it didn't make any difference. For other subjects it probably (I would think) would.

Thanks for the comments and info,
keith



May 29, 2017 at 07:36 PM
Paul Mo
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p.1 #9 · p.1 #9 · canon 100mm f/2.8 non-L macro


http://www.ebay.com/itm/Very-Clean-body-and-Lens-Canon-EF-100mm-f-2-8-Macro-Lens-From-Japan-/232352476661?hash=item3619496df5:g:oTsAAOSwblZZK37O

Okay, clearing up my own confusion:

The lens above in EF mount - pre-USM.

100mm f2.8L USM

100mm f2.8L USM IS.



May 29, 2017 at 07:51 PM
Ernie Aubert
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p.1 #10 · p.1 #10 · canon 100mm f/2.8 non-L macro


I've never used a rail; I can't help but wonder: Moving the camera on the rail moves the sensor, thus changing the perspective (and the size of the image on the sensor). Is what's being said here that the perspective (and image size) changes even more by changing the focus while the sensor stays stationary? Interesting concept...


May 29, 2017 at 07:51 PM
Peter Figen
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p.1 #11 · p.1 #11 · canon 100mm f/2.8 non-L macro


Having done a lot of focus stacking with a range of Canon lenses from 24mm to 100 Macro, and having done both incremental focusing and using a RRS Macro Focusing Rail, cobbling between ten and sixty images together in Helicon or Xerene, I can say without a doubt that using your focusing ring is a better alternative to moving the entire camera/lens on a rail. There is too much perspective changing on the rail, and while there is breathing using the focusing ring, that's pretty easily dealt with in software.


May 29, 2017 at 08:50 PM
beanpkk
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p.1 #12 · p.1 #12 · canon 100mm f/2.8 non-L macro


Paul: Mine has USM, but is not an L. Maybe they don't make it any more? Mine is the one the L replaced/updated I think. It's listed in the Canon refurb site as 100mm f/2.8 Macro USM.

Ernie: Moving the camera changes the perspective and the field of view...that's right. In my dandelion setup, with the lens at Minimum Focus Distance (MFD), refocusing to MFD + 1.5" has a huge effect on the field of view, much more than just moving the camera that distance. That change with focusing is called "focus breathing" (for some odd and unknown reason :-) ) and the effect in the Canon 100mm f/2.8 Macro USM lens is huge. I have never looked through the newer 100mm f/2.8 Macro L lens so can't comment but I would bet it does pretty much the same thing. For stacking the first step is image alignment, necessitated by the fact that the field of view/image framing changes with each shot. This will always be the case using a rail, because the camera moves. But if there were a lens (perhaps the old 100mm non-L non-USM mentioned above) that doesn't focus breathe, we could leave the camera and just refocus and not need to do an alignment.

I'm open to correction at any point on this stuff.

keith



May 29, 2017 at 08:58 PM
Ernie Aubert
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p.1 #13 · p.1 #13 · canon 100mm f/2.8 non-L macro


I have that lens (100 f2.8 USM Macro); I think I'm motivated to do some MFD experimentation - well, with focus changes anyway, since I don't have a rail. I also have a Zeiss 2/100 Makro, so I may just as well try with that too. I just need to get one of those round tuits...


May 29, 2017 at 09:31 PM
charlyw
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p.1 #14 · p.1 #14 · canon 100mm f/2.8 non-L macro


Don't let the non-internal focusing of the old 100mm f/2.8 1:1 macro lens fool you, even that exhibits considerable focus breathing - as do the similarly designed old Tamron 90mm (non VC) and Tokina 105mm...

Focus breathing is a problem in stacking but the alternative to use a focusing rail isn't problem free either. the big advantage of a focusing rail is that you can make arbitrary length steps in whatever increments you need - something which doesn't work even when you use your camera tethered to make minimal focusing steps with a controller software. Couple that with the ability to be able to do larger steps when called for - recently I was waiting for a small solitary bee to emerge from a Serapia orchid (providing night time shelter is their pollinisation strategy) - I didn't know how far the bee would come out or how large it would be, all I saw for two hours was the backside of it. When it finally came out I had to readjust focus precisely but yet take the DOF into account (you don't want to focus at the closest bit of the bee, that would waste half of your available DOF) which the focusing rail enabled me to do and I got the shot where the bee just wiggled out of the flower - without focusing rail I would have missed the shot for certain...



May 30, 2017 at 02:26 AM
beanpkk
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p.1 #15 · p.1 #15 · canon 100mm f/2.8 non-L macro


You can see focus breathing just by aiming the camera/lens at something say 10 feet away and then turning the focus ring. Yes, the subject will become blurred, but you can see how the framing changes.

Using a rail certainly will allow more accurate and predictable focusing steps than adjusting the focus ring on the lens. On my lens, there is a little play in the focus ring, adding just a bit more uncertainty to the process. OTOH my rail is a cheap one and works well but there is a bit of movement there too. As long as you a) have a rail, b) aren't too lazy to get it out (), c) your subject depth doesn't exceed the length of the rail, and d) using the rail causes less framing change than refocusing the lens, then using the rail is the best option. The kicker is (b) for me! I think my rail was in the $40 range. And for reasons charlyw stated, using the rail may be better even if (d) doesn't hold true for the lens in use.

Good discussion -- thanks for the comments.

keith






May 30, 2017 at 06:03 AM
charlyw
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p.1 #16 · p.1 #16 · canon 100mm f/2.8 non-L macro


beanpkk wrote:
As long as you a) have a rail, b) aren't too lazy to get it out (), c) your subject depth doesn't exceed the length of the rail, and d) using the rail causes less framing change than refocusing the lens, then using the rail is the best option. The kicker is (b) for me! I think my rail was in the $40 range. And for reasons charlyw stated, using the rail may be better even if (d) doesn't hold true for the lens in use.


An here comes the rub, my focusing rail costs about as much as the non-L Canon 100mm f/2.8 USM lens does - so b is a given, else I wouldn't have spent as much (and it is a precision instrument which is a joy to use)...



May 30, 2017 at 09:20 AM
beanpkk
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p.1 #17 · p.1 #17 · canon 100mm f/2.8 non-L macro


Wow, charlyw you must have gotten a good one. I'm curious which one it is? At the camera store I went to (I bought mine locally) they only had two or three options, and none were in the $hundreds price class. Mine has a little play in the mechanism, but that's easily handled with the tightening screws, and mine goes both forward-backward and side-side, about 6 inches. It appears to be calibrated in mm. Made of metal, heavy (!), etc. Not a precision instrument, but good enough for a hopeless guy like me! On the other hand maybe (b) would be less of an issue if I had one that was a joy to use like yours! Mine is kind of a pain.

keith



May 30, 2017 at 10:05 AM
charlyw
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p.1 #18 · p.1 #18 · canon 100mm f/2.8 non-L macro


beanpkk wrote:
Wow, charlyw you must have gotten a good one. I'm curious which one it is?


Novoflex Castel Cross...



May 30, 2017 at 11:21 AM
scalesusa
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p.1 #19 · p.1 #19 · canon 100mm f/2.8 non-L macro


A really informative video that not only evaluates different focus rails, but using the lens focus ring, and using bellows. Each has its strong points.

https://lensvid.com/gear/choosing-the-best-focusing-rail-for-macro-photography/




Jun 01, 2017 at 04:54 PM





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