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Working distance & focus - Canon 100mm macro w/Kenko tub
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JimGnitecki



Joined: 12 Sep 2017
Posts: 28

PostPosted: Wed Sep 13, 2017 12:32 pm    Post subject: Working distance & focus - Canon 100mm macro w/Kenko tub Reply with quote

I am new to macro and trying to determine my capabilities when shooting insects and tidal flats sea creatures. The subjects are generally pretty small. "Giant" ones are 2 or 3 inches across while the more typical subjects are 1/4" to 3/4" including legs and other protrusions! Then there is the issue of shooting them when they are under a 1 or 2" layer of seawater!

I am using a Canon 70D with Canon 100mm Macro lens, and have the 3-piece set of Kenko extension tubes, which support AF and TTL exposure via electrical contacts pass-through.

My setup allows shooting either via viewfinder, or Live View, or Live View via iPad using the Canon Camera Control software.

I want to achieve 1x to 3x macro if possible, as the subjects are so small and I want to pick up the details of hair, scales, eyes, etc to the maximum extent I can.

Next equipment add-on will be Yongnuo YN24EX E-TTL Macro Flash, even though the beaches are normally pretty bright, as this should enable me to use a smaller aperture for a deeper focal depth, as focal depth is THE big challenge, and the built-in flash is useless because the lens shades the subject.

I am also planning to buy a full license for Helicon Focus and Helicon Remote (The Helicon remote to replace Canon Camera Control.

With this starting point:

- How do I optimize manual focusing?

- How small a working distance can I achieve using 1 or more Kenko tubes?

- How high a magnification can I achive, still geting reaosnable quality results?

Jim G
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Chris S.
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Joined: 05 Apr 2009
Posts: 2815
Location: Ohio, USA

PostPosted: Wed Sep 13, 2017 11:42 pm    Post subject: Reply with quote

Jim,

I’m by no means the best person here to answer all your questions (not a Canon shooter), but welcome to the forum! Very Happy

Shooting creatures in tidal flats sounds like a wonderful macro specialty. I look forward to seeing the images you share.

Quote:
the more typical subjects are 1/4" to 3/4". . . .

I want to achieve 1x to 3x macro if possible, as the subjects are so small and I want to pick up the details of hair, scales, eyes, etc to the maximum extent I can.

If budget permits, you might consider getting a Canon MP-E 65mm lens for your work. This is a 1x-5x zoom macro lens whose sweet spot seems to be about 1-3x. (I’ve never used this lens, but quite a few members of this forum use it a lot.) Since you are already shooting Canon, and are undertaking a rather demanding field-macro specialty, this lens seems ideally suited to your work.

Using your 100mm macro lens on, say, 68mm of Kenko extension tubes, will not get you to 3x. I’m guessing it will get you close to 2x. (The actual figure can be computed mathematically; but one of the inputs to the calculation is the focal length of the lens, and most macro lenses are designed to reduce focal length as you focus closer—so I’m taking a guess that your lens is actually 60-70mm when focused at 1:1. In the real world, I prefer to simply test the lens/tube combo.)

Quote:
How high a magnification can I achieve, still getting reasonable quality results?

The performance of your 100mm macro lens on 68mm of extension may disappoint you. Such lenses usually perform better, when shooting at magnifications above 1x, if they are reversed (turned around and used backwards). While reversing a lens in the studio is doable, reversing a lens in the field is a pain.

The Canon MP-E 60mm lens neatly sidesteps these issues. (FYI, there are other ways to sidestep them, but that’s a long conversation, and this lens seems ideally suited to your particular situation.)

Quote:
How do I optimize manual focusing?

When you’re shooting near 1x and higher magnifications, set your lens to the desired magnification, and focus by moving the camera closer or farther from the subject. In such scenarios, attempting to focus with the focus ring causes problems.

Quote:
How small a working distance can I achieve using 1 or more Kenko tubes?

Most of us want a long working distance, not a small one!

The only real way to determine this is to measure. As you have the camera, lens, and tubes, you are probably in a position to do this?

Quote:
Next equipment add-on will be Yongnuo YN24EX E-TTL Macro Flash, even though the beaches are normally pretty bright, as this should enable me to use a smaller aperture for a deeper focal depth, as focal depth is THE big challenge, and the built-in flash is useless because the lens shades the subject.

Nearly every member of this forum has battled with the challenge of limited depth field inherent in macro work. For me, this presented an impenetrable wall that no photographer could break through, until the advent of focus stacking roughly a decade ago. Software such as Zerene Stacker and Helicon Focus, along with concomitant hardware developments, let us burst through this wall—and the photographic results have been amazing.

Equally, we have also faced the difficulties of light control in field macro. As you say, even when there is plenty of sun, flash is often required for field macro. My bet is you’ll need this not just to permit smaller apertures, but to freeze motion, and to direct the light to model your subjects well.

Quote:
Then there is the issue of shooting them when they are under a 1 or 2" layer of seawater!

This is potentially a huge issue! In your shoes, I would perhaps shoot these creatures in situ only up to 1x or so. For higher magnifications, how about making small, portable aquaria out of microscope slides, cover glass, and silicon sealant, and taking these into the field? (Be aware that microscope slides can be obtained in larger sizes than the normal 1-inch by 3-inch; 3-inch by3-inch are available.) If you had a selection of these, on a table placed on the beach, with flashes mounted on flexible arms on the table, and the camera mounted on the table, you might combine elements of studio macro and field macro to very good effect.

Cheers,

--Chris S.
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JimGnitecki



Joined: 12 Sep 2017
Posts: 28

PostPosted: Thu Sep 14, 2017 6:02 am    Post subject: Reply with quote

Thank-you, Chris. Your advice is helpful! Your idea of the mini-aquariums has gotten me thinking!

The question on how small a working distance I can achieve is based on the desire to "fill the frame" with the subject. My reasoning has been that the closer I can get, the larger the subject becomes in the photo and thus the greater the detail. This is limited by two things: (1) the desire of the critter to scurry off if I get too close, and (2) the ability of the lens to attain focus at really short distances.

I have done very limited testing at home on working distances and focusing, using inanimate objects as test subjects (because they don't try to scurry off during the experiment!) and have managed to get some photos of as high as 3X macro, but focusing is tricky once I get beyond about 1.5 to 2X macro.

It APPEARS to me that I can reliably focus down to about 5-1/2 inches of working distance with the Canon 100mm macro, but any closer and the focus becomes problematic. I plan next to experiment with the Kenko extension tubes, seeing which length of tube, or which combination of tubes, allows me to get closest with good focus.

I am working within a budget (retired, so limited income), and have been keeping an eye out for used bargains on Craigslist and Kiji. The Canon 100mm macro is an early result of those efforts - a very attractive deal! I have been reading about the MP65E macro lens, and there are 2 challenges there: (1) cost of even a used one, and (2) they are apparently a real challenge to learn to use properly! The "learning to use" challenge does not scare me, but the odds of finding a used one for a price I can afford seem low, especially since I am located on Vancouver Island, with a single return ferry trip to even nearby metro Vancouver costing about $130 for me and the car! Buying a used one without actually seeing and testing it first seems unwise.

But yes, if I can engineer acquiring one of those, I agree it would be more suitable for my smaller (1/4 inch to 1/2 inch) target subjects. The 100mm macro is suitable, and frankly better, and far easier to use, for many of my larger (e.g. 2 inch) target subjects.

I realize that with a 20 megapixel sensor, I can simply take the photos of 1/4 inch subjects from 5-1/2 to 7 inches working distance and then crop the photo, but I am fascinated by the microscale hairs, antennae, scales, and surface textures that these creatures have, and need as much resolution as I can reasonably attain!

I'll keep working on this . . .

Jim G
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banania



Joined: 16 Sep 2013
Posts: 152

PostPosted: Fri Sep 15, 2017 11:44 am    Post subject: Reply with quote

Hello, you can also use teleconverters like Kenko 2X teleconverter. I have been using that one with Canon 100mm L macro and it works fine and takes you to 2x. I have also Kenko extension rings but never really use them... I feel 2x teleconverter takes me further than the extension rings.

Never tried to combine those... maybe I ought to test this combo. That would take me to 3.3X, I think?

Another tip, which is maybe too obvious to mention, is to use a polarizing filter. I have a linear polarizer attached to my 100mm macro and feel that it is a must as it both protects the lens, kills reflections and deepends colors, especially the greens come more photegenic as they loose the dull greyish tone. As you are shoóting stuff under water it is a natural choice, but it is very useful in all macrophotography.

Henri
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JimGnitecki



Joined: 12 Sep 2017
Posts: 28

PostPosted: Fri Sep 15, 2017 1:28 pm    Post subject: Reply with quote

banania wrote:
Hello, you can also use teleconverters like Kenko 2X teleconverter. I have been using that one with Canon 100mm L macro and it works fine and takes you to 2x. I have also Kenko extension rings but never really use them... I feel 2x teleconverter takes me further than the extension rings.

Never tried to combine those... maybe I ought to test this combo. That would take me to 3.3X, I think?

Another tip, which is maybe too obvious to mention, is to use a polarizing filter. I have a linear polarizer attached to my 100mm macro and feel that it is a must as it both protects the lens, kills reflections and deepends colors, especially the greens come more photegenic as they loose the dull greyish tone. As you are shoóting stuff under water it is a natural choice, but it is very useful in all macrophotography.

Henri


I had not researched teleconverters yet, so thanks for that suggestion! And yes, I did not mention it but do have a polarizing filter on the lens.

Jim G
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Lou Jost



Joined: 04 Sep 2015
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PostPosted: Fri Sep 15, 2017 1:41 pm    Post subject: Reply with quote

Quote:
Never tried to combine those... maybe I ought to test this combo.


I regularly use both in the field; if the prime lens is very good, this can give good results. Best order is lens + tube + TC + camera.
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JimGnitecki



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PostPosted: Fri Sep 15, 2017 1:47 pm    Post subject: Reply with quote

Lou Jost wrote:
Quote:
Never tried to combine those... maybe I ought to test this combo.


I regularly use both in the field; if the prime lens is very good, this can give good results. Best order is lens + tube + TC + camera.


I did not even think about the "stacking order" when using a teleconverter simultaneously with extension tubes. So the order in which they are mounted does matter! What symptoms do you get if you put them on in an incorrect order?

Jim G
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Lou Jost



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PostPosted: Fri Sep 15, 2017 3:02 pm    Post subject: Reply with quote

Nothing major, but the teleconverter is designed to provide an image at a certain distance from the flange, and this order respects that design constraint. Lenses on the other hand are usually more robust to changes in extension.
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JimGnitecki



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PostPosted: Fri Sep 15, 2017 5:04 pm    Post subject: Reply with quote

I THINK I just achieved 4.1X macro, using the Canon 100mm Macro lens with 68mm thickness of all 3 Kenko extension tubes used simultaneously.

I set my Canon 70D down on a rigid table, with the lens and the 3 extension tubes in place. I activated built-in flash and Live View, and placed a bright yellow Sharpie highlighter onto a rigid pedestal of books to get it to the right approximate height to center the word "Highlighter" within the Live View frame. I set the lens for its maximum magnification (0.31 meter marking). I focused manually by sliding the camera/tubes/lens assembly towards and away from the Sharpie. It was easy to detect maxium sharpness at f5.6 because when focused "perfectly", the lettering in the word "Highlighter" showed clearly its print imperfections and wear points. A very small movement inward or outward from the Sharpie quickly blurred the lettering. I snapped the photo manually with the shutter button, as a remote was not necessary to get a clean image.

Please check my math:

The actual vertical height of the "Highlighter" lettering is approximately 3/64" = 0.047".

On my computer screen, the photo frame of the resulting shot is 5.5" in height. This corresponds of course to the 24mm height of a standard frame.

The Highlighter lettering in this frame is approximately 1-1/8" high. This means it is 1.125/5.5 = 0.2045 of the vertical height of the frame.

That makes the image of the highlighter word in the frame 0.2045 x 24 = 4.9mm high or 0.193"

0.193" divided by the actual height of 0.047" = 4.1X actual size

Did I do this math correctly?

Also, the working distance for the lens alone was 6 inches. With the extension tubes in place, that became 4.5 inches.

Jim G


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Lou Jost



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PostPosted: Fri Sep 15, 2017 5:06 pm    Post subject: Reply with quote

You know you can just take a picture of a ruler.
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JimGnitecki



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PostPosted: Fri Sep 15, 2017 5:13 pm    Post subject: Reply with quote

Lou Jost wrote:
You know you can just take a picture of a ruler.


I don't have a ruler with good enough markings! They are very ragged.

Jim G
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Lou Jost



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PostPosted: Fri Sep 15, 2017 5:19 pm    Post subject: Reply with quote

It doesn't matter, as long as you can read the mm marks.
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rjlittlefield
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PostPosted: Fri Sep 15, 2017 6:08 pm    Post subject: Reply with quote

Here's what Lou is talking about.



This is shot with a Canon T1i camera (sensor size 22.3mm x 14.9mm), using a Canon 100 mm f/2.8 L IS USM macro lens and 68 mm of Kenko tubes -- just the same as yours except that the 70D sensor is a hair bigger at 22.5mm x 15.0mm.

This image shows 11.55 mm of ruler, so the magnification is 22.3/11.55 = 1.93X .

Notice that I've used the actual sensor size, not 36 mm which would be the width "of a standard frame", as you put it.

Here at photomacrography.net, the convention is that we talk in terms of actual optical magnification unless otherwise specified. At some other places people use a scaled magnification that normalizes everything to a 24x36mm frame. We don't do that. In both worlds, a 1X macro lens images an area of size 22.3x14.9 mm when used on a 22.3x14.9 mm sensor. But we still call that 1X, even though imaging 22.3 mm across the width of a full-frame 36 mm sensor would be 1.61X .

--Rik
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JimGnitecki



Joined: 12 Sep 2017
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PostPosted: Fri Sep 15, 2017 7:00 pm    Post subject: Reply with quote

rjlittlefield wrote:
Here's what Lou is talking about.



This is shot with a Canon T1i camera (sensor size 22.3mm x 14.9mm), using a Canon 100 mm f/2.8 L IS USM macro lens and 68 mm of Kenko tubes -- just the same as yours except that the 70D sensor is a hair bigger at 22.5mm x 15.0mm.

This image shows 11.55 mm of ruler, so the magnification is 22.3/11.55 = 1.93X .

Notice that I've used the actual sensor size, not 36 mm which would be the width "of a standard frame", as you put it.

Here at photomacrography.net, the convention is that we talk in terms of actual optical magnification unless otherwise specified. At some other places people use a scaled magnification that normalizes everything to a 24x36mm frame. We don't do that. In both worlds, a 1X macro lens images an area of size 22.3x14.9 mm when used on a 22.3x14.9 mm sensor. But we still call that 1X, even though imaging 22.3 mm across the width of a full-frame 36 mm sensor would be 1.61X .

--Rik


Ok, I get the way it is done now. Thanks!

Jim G
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JimGnitecki



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PostPosted: Fri Sep 15, 2017 7:16 pm    Post subject: Reply with quote

In its specifications for the 70D, Canon shows the sensor as being 22.5mm x 15.0mm (APS-C).

So, redoing my math to allow for the APS-C sensor size of 15.0mm height:

The actual vertical height of the "Highlighter" lettering is approximately 3/64" = 0.047".

On my computer screen, the photo frame of the resulting shot is 5.5" in height. This corresponds of course to the 15mm height of the sensor in the 70d.

The Highlighter lettering in this frame is approximately 1-1/8" high. This means it is 1.125/5.5 = 0.2045 of the vertical height of the frame.

That makes the image of the highlighter word in the frame 0.2045 x 15.0 = 3.07 mm high or 0.121"

0.121" divided by the actual height of 0.047" = 2.57X actual size

Is that correct?

Jim G
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