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05-09-2011, 04:09 AM   #1
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Macro beyond 1:1

Hello...

I want to get more serious with macro photography (mostly plants and insects). And I'm wondering what lens to get for my K20D. One thing I would be very much interested in is achieving magnification greater than 1:1 (say 2:1 or even 4:1). I imagine that would be possible by using a 1:1 macro lens with extension tubes provided that the focal length was long enough to maintain a viable working distance. Say at least 100mm.

I understand that getting more DoF than a sheet of thin paper will be a big issue when trying to get to larger magnification. That means that I will need to stop down quite a bit. In consequence I'll need to be making sure to get enough light onto the subject. I expect a tripod to be a must for this endeavor :-) Any experiences with regards to what is still practical in terms of magnification and aperture/lighting when shooting macro outdoors would be very interesting for me.

Are there any lenses that offer magnification greater then 1:1 without additional equipment such as extension tubes?

Is using extension tubes to go beyond 1:1 even a good idea? Are there other options? And if you know of a lens you would recommend for this sort of scenario, I'd love to hear about it.

Thanks,
Lars

05-09-2011, 05:35 AM   #2
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I have never tried this but you could try using additional extension tubes beyond the normal set of three used to get to 1:1 life size.

Consider the fact that you may be getting a little bigger then life anyways on a D-slr considering the fact that the image is cropped with a macro lens plus extension tube set. I do not know how the extra tubes will affect the picture but it is worth the time to find out.
05-09-2011, 05:52 AM   #3
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Lars,

Among long macros are the Pentax FA* and A* 200/4ED ones. I assume they are discontinued and very expensive.
I recently got the Sigma 180/3.5 EX macro (also discontinued), it weighes ~1kg so I imagine it needs a tripod, even if I only have tried it handheld. With obviously various success.
Also the Sigma 150/2.8 macro might be available new in Pentax mount after all (I did think it wasn't) and could be an option if so.

Seb.
05-09-2011, 06:10 AM   #4
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Welcome Lars. I am far from an expert with Macro beyond 1:1 but do occassionally push it as far as 3:1 with a combination of accessories I just happened to have on the shelf to try. Since AF is useless, I keep an old MF 100/3.5 Phoenix mounted on a rail with a K20D and extend its native 1:1 ability with extension tubes, a Raynox 150 clip-on, and a Pentax 1.7x TC. I have not done enough controlled work with above to say which provides the best overall function as all 3 have advantages I use at times. Unfortunately, I don't have the patience for stacking so have not any real uses for greater than 1:1 shooting. But it was fun to play with and I did learn that unlike tele-extenders where the IQ can visably suffer, the super-macro shots with this combination looked sharp and colorful in spite of painfully thin DOF at f22.

- extension tubes; cheap for contact-less variety, adjustable,
- Raynox 150, maybe 250 also; inexpensive and very convenient except if using ring/macro light
- 1.7x (or any other) TeleConverter; you probably already have one!

Just a thought to achieving high macro ratios with parts you may already have lying around.

05-09-2011, 06:35 AM - 4 Likes   #5
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QuoteOriginally posted by stevbike Quote
Consider the fact that you may be getting a little bigger then life anyways on a D-slr considering the fact that the image is cropped...
The crop-sensor doesn't affect magnification. A 1:1 setup at close-focus distance will deliver 1:1 images whatever the frame size.

QuoteOriginally posted by lars.o Quote
Are there any lenses that offer magnification greater then 1:1 without additional equipment such as extension tubes?
No.

QuoteQuote:
Is using extension tubes to go beyond 1:1 even a good idea? Are there other options?
There are two ways to increase magnification: extension, or supplementary optics.

First, some definitions. A camera lens is one that can be directly mounted on a camera. A camera macro lens has extension built into its body, such as my Macro-Takumar 50/4 or Vivitar-Komine 90/2.8 macro. An enlarger or bellows-macro lens has no focusing mechanism, is meant to be used on extension. Extension means bellows and/or tubes; a reversed camera lens with a deep front inset also provides some extension.

Increased magnification with a macro or non-macro camera lens, or to an enlarger or bellows-macro lens, can require adding LOTS of extension, especially with longer focal-length lenses. So if you have a 1:1 100mm camera macro lens, you'll need another 100mm of extension to reach 2:1. I have used longer such setups but only with a shoulder-stock mount for stability -- and the gear looks like a firearm!

Adding extension is easier with shorter lenses. A 1:1 50mm camera macro lens only needs another 50mm of extension to reach 2:1. But working just two inches away, you will probably scare the bugs! Non-macro camera lenses can be mount-reversed, with extension added, for fine macro results. But a reversed prime still has a working distance under two inches.

One trick I recently discovered: I put a lousy A35-80/4-5.6 zoom, Pentax's worst, on a mount-reversal ring, and got good macro results! At 35mm it reaches about 2:1; at 80mm it reaches around 1:2 at 6in / 15cm working distance, and can also focus past infinity. But high magnification still means working *very* close.

So, what about supplementary optics? A corrected close-up adapter like the Raynox DCR-150 or -250 allows for pretty close work with decent results. But the classic tool for clean optics is with reverse-stacking of lenses. Magnification is a simple ratio. The lens mounted on the camera is the PRIMARY; the reversed lens is the SECONDARY; and magnification is the ratio of focal lengths, PRIMARY : SECONDARY. So a 50mm lens reverse-stacked on a 100mm gives 100:50 or 2:1. Stacking a 35mm lens onto a 105mm gives 105:35 or 3:1. Extreme magnification can be reached this way! BUT... working distance will be under two inches. Reversed primes always have a working distance equal to their register, which for Pentax lenses is around 4.5cm.

A teleconverter is another form of supplementary optics. This will increase your working distance by its TC X-factor, but will also degrade image quality to some extent. This IQ loss probably won't be too great with a TC that is well-matched to the camera lens. I have even use a variable-magnification macro TC. It worked for me; but then, my standards are low.

So, the awful truth: For great magnification you must either work very close, or use LOTS of extension on longer lenses, or degrade image quality a bit. A magic wand does not exist. The laws of optics are merciless.

Last edited by RioRico; 05-09-2011 at 06:43 AM.
05-09-2011, 06:46 AM   #6
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what RonRico said, +1
05-09-2011, 07:09 AM   #7
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QuoteOriginally posted by lars.o Quote
Hello...

I want to get more serious with macro photography (mostly plants and insects). And I'm wondering what lens to get for my K20D. One thing I would be very much interested in is achieving magnification greater than 1:1 (say 2:1 or even 4:1). I imagine that would be possible by using a 1:1 macro lens with extension tubes provided that the focal length was long enough to maintain a viable working distance. Say at least 100mm.

I understand that getting more DoF than a sheet of thin paper will be a big issue when trying to get to larger magnification. That means that I will need to stop down quite a bit. In consequence I'll need to be making sure to get enough light onto the subject. I expect a tripod to be a must for this endeavor :-) Any experiences with regards to what is still practical in terms of magnification and aperture/lighting when shooting macro outdoors would be very interesting for me.

Are there any lenses that offer magnification greater then 1:1 without additional equipment such as extension tubes?

Is using extension tubes to go beyond 1:1 even a good idea? Are there other options? And if you know of a lens you would recommend for this sort of scenario, I'd love to hear about it.

Thanks,
Lars
Yes there is, but not in PK mount The canon MPE-65mm can go from 1x - 5x all by itself.

I shoot above 1:1 exclusively (I personally hate 1:1) and use extension tubes most of the time to do it. If you want 100mm of working distance I cant help you.

But what I will say is that if the objects you shoot are inanimate, look into focus stacking. Stopping down a ton will result in diffraction making the image soft.
05-09-2011, 07:23 AM   #8
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QuoteOriginally posted by RioRico Quote
The crop-sensor doesn't affect magnification. A 1:1 setup at close-focus distance will deliver 1:1 images whatever the frame size.
While the lens magnification remains the same, wouldn't a cop-sensor will see better magnification if we consider subject size to image size on sensor.

05-09-2011, 07:53 AM   #9
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Wow, RioRico, thanks for the comprehensive reply! This does helps a lot...

Is there a way one can calculate the working distance for 1:1 from the focal length of a camera macro lens? Once I got that, I'd assume when adding extension to reach 2:1, I would get to the half that distance, right? For a 100mm Macro, I read about working distances of around 150mm for 1:1. Now if I were to add 100mm of extension in order to get to 2:1, would I need to get as close as half the working distance (say 75mm) or will the extension factor into that so I would get as close as 65mm?

When reverse-stacking a prime on another lens, how close does the primary lens need to be able to focus? Will it be necessary to use extension tubes or is it necessary to increase the distance between primary and secondary lens?

How far can a macro lens be stopped down without getting noticeable quality degradation from light diffraction? Are there lenses that can be stopped down beyond f22? At 150mm working distance with a 100mm lens, that would indeed be looking at a DoF of around 1mm at f22. Ouch. Damn those laws of physics ;-)
05-09-2011, 07:57 AM   #10
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"The crop-sensor doesn't affect magnification. A 1:1 setup at close-focus distance will deliver 1:1 images whatever the frame size."

I was looking at it from the point of view from comparing the lens when used on a film to D-slr camera. Yes when you just look at from the lens on the camera without camparing the two camera formats, it is still just 1:1.
05-09-2011, 08:05 AM   #11
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For diffraction, you wont see it much @ 1:1 but it is still there past ~ F/10 depending on the lens. As the magnification increases so does the diffraction at any given aperture. Basically F/10 for instance at 5x magnification would be nearly useless IMO. Hence the creation of photo stacking.

an extreme example of my point:




@ F/5.6 and 5 image stack crop




@ F/16.....

and full sized version: http://farm5.static.flickr.com/4107/5084205236_d40f350f3f_o.jpg

That should give you a rough idea.
05-09-2011, 08:30 AM   #12
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There is a lot of good info in this thread: ways get closer than 1:1
05-09-2011, 09:09 AM   #13
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Here is a sampling of some pictures I took today. The top one is the 50mm f4 macro without anything added. The bottom is the same lens on the 3 extension tubes and a 2x converter on it. I just wanted to see how it would look.

05-09-2011, 09:15 AM   #14
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QuoteOriginally posted by yusuf Quote
While the lens magnification remains the same, wouldn't a cop-sensor will see better magnification if we consider subject size to image size on sensor.
The definition of 1:1 is that the size of the image on the frame (film or sensor) is the same as the size of the subject.

Let's say I have a lens setup for 1:1, and I'm shooting a ruler. On a full-frame 36x24mm camera (film or digital), I'll see ~1.5 inches in the viewfinder. On a half-frame 24x18mm film camera, or ~25x16mm APS-C camera, I'll see ~1 inch in the viewfinder. The recorded image magnification remains the same. The cropped frame chops off the edges of the projected image, that's all.

I can rig my KW G&T Patent Etui 6.5x9cm folder (with groundglass back) for 1:1 also, and I'll see ~3.25 inches on the groundglass. If I were shooting film in all those, and I stacked the various-sized negatives on top of the ruler, everything would line up. The recorded details are all the same size. The ruler ticks are all the same distance apart. The larger frames just capture more of the projected image.

And the focal length of the lens makes no difference to magnification. A longer lens just allows/forces you to work further from the subject. A non-reversed lens can't focus closer than its focal length. So, on any camera, working distance for 1:1 with a 24mm lens is one inch; for a 50mm lens, two inches; for a 100mm lens, four inches; etc. (Note: I refer to non-reversed non-zoom lenses. Reversal and zooms have different working distances.)

To really get into this, read the BIBLE (old testament, anyway) of close-up and technical shooting [ Field Photography: Beginning and Advanced Techniques by Alfred A. Blaker ] which is still an incredible deal at Amazon.
05-10-2011, 01:15 AM   #15
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So much good information. You guys are awesome!

I think I'll have a try with a bellows setup. I am also dabbling in B&W film photography and happen to have an enlarger with some Rodenstock optics (50mm APO, 80mm and 120mm). I'll let you know how it goes when I'm able to get my hands on a usable bellows thingy...
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