Achieving High Magnifications in Macrophotography
Achieving extremely high magnifications in Macrophotography
Here is some info I put together for those interested in how to achieve very high magnifications in Macrophotography. All this applies to all types of subjects including our beloved trichomes The article below is for magnifications greater than 1:1 with a DSLR . Up to 1:1 you can just use a standard macro lens with no additional equipment .
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Basic Tools
SLR camera body, Lenses (preferably Macro Lenses or Specialized microphotography lenses or Cine lenses), Teleconverters , Extension Tubes / Bellows
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Coupling lenses
One good way to achieve results up to 10x is to use stack two lenses together . For example a 28mm lens reversed in front of the 200mm will give you 200/28= 7x magnification with superb quality if the optical marriage is good between the two lenses . This is a good way to achieve automatic diaphragm/metering connections between the lens and the body . The reversed lens must have aperture ring , set it one or two stops slower ( if it is f2.8 set it to f4 ) . Now control everything as you would normally do . TTL flash and everything works as it should . Both lenses should be primes , as zooms will not give sufficient quality . You can couple the two lenses with a coupler ring . If the filter rings do not match ( eg. 49mm and 52mm ) use a step-up / step-down ring . What you are basically doing , is using the reversed lens as a close up filter , but now the lens is used as a very high quality one . Now this is good for up to lets say 10x . You can always use photo tape or electrical tape but use one that doesnt leave sticky stuff behind . It is good way to do some tests with your existing lenses .
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Specialized lenses for very high magnifications
The best lenses for macrophotography from 5x magnification and up to 30-40x is achieved with specialized lenses ... the notorius Leica Photar , Carl Zeiss Luminar , Nikon Macro Nikkor ( not the Micro ) , Canon macro photo , Olympus Zuiko Macro . All these lenses are highly corrected for high magnifications and most of the small focal length lenses , that is from 12mm to 20mm are corrected from 5-20x . Remember that any lens is only corrected for a specific magnification . Most conventional lenses are optimized for infinity or very low magnifications . Most macro lenses are optimized for 1:10 or 1:5 .. depends on the manufacturer .
The Photars are very expensive but the best , the Luminars are very good as well , expensive and not so rare . The Macro Nikkors are VERY rare . The Canon macro photo 20mm is not the best but quite affordable , as is the Olympus Zuiko Macro which is better than the Canon one , and faster too . There are some other macro specialized lenses which can be bought for quite cheap . A good leica ( leitz ) photar 12.5mm will sell for 200-300 usd easily on Ebay but the quality is EXCEPTIONAL , so is the Luminar's 16mm quality . These lenses use RMS mount which a specialized screw mount used for microscopes objectives . And of course you can only use them with bellows ( or extensions tubes of course ) .
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Reversing a lens
When we work more than 1:1 , the lens must be reversed for high sharpness. The reason is because lenses are designed to work best if the the distance between lens and sensor is smaller than lens subject . Highly corrected macro lenses such as the photar / luminar / canon macro photo / olympus zuiko macro and other are already reversed ( the design is reversed ) so no need to reverse them again.
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Cine lenses
Now because the specialized lenses I described above are quite expensive ( although you can definitely buy a used one quite cheap like 100usd , for a 10-20mm lens ) there is another way to achieve very good quality with less cost . This is to use a Cine lens but you must use it reversed . There are some tried cine lenses ( from 16mm and 8mm cine formats ) that work very good , almost as good as a Luminar or a Photar in magnifications from 10x to 20x . For the 16mm format, 25mm lenses are 'normal' and for the 8mm cine format 12.5/13mm lenses. . The cine lenses have to be reversed to work properly in macrophotograhy. The only problem is it is quite difficult to reverse them on a bellows . The best technique is to use their filter thread . If you cannot find an adapter , cut a hole from a plastic Nikon F ( or whatever the mount ) cup and be innovative .. ( use glue tape whatever ) . Ugly, inelegant , works.
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Focal length
Also remember that small focal lengths are the best choice for high magnification work ... we generally do not want more than 25mm in most SLR cams. I would choose a lens which falls between 10-25mm for extreme magnifications . The reason is that you can get extreme magnification by using less extension. This is really important for minimizing the problems from diffraction and loss of light due to using lots of extension. Microscopes use small focal length lenses for these reasons.
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Diffraction problems and effective f-stops
The other problem is diffraction. That is one of the reason most of the macro photos are soft and blurry. The marked f-stop is only equal to the effective f-stop only at 'infinity'...and then again there is some light loss when light passes through the glass elements. When we use a 50mm macro lens at 2x magnification and we use the marked f-stop f/16 ... the effective f-stop is not f/16 ... it is more like ~f/40 . There is a formula to calculate this. A modern digital APS-C sensor becomes 'diffraction limited' at about f/11 , depends on Sensor size and mpixel . So anything more than an 'effective fstop' of around f/11 and the quality degrades dramatically. This is the reason we must use a wide aperture when we work with more than x4 magnification which unfortunatelly then leads to shallow depth of field. Specialized macro lenses for high magnifications ( Photars/Luminars etc ) are best from their widest aperture and give less good results at higher f-stop numbers. On the other hand most macro lenses that go up to 1:1 are sharpest between ~f4 and ~f11 . So if we work with high magnifications ( more than 4x ) it is best to use a f4-f5.6 , use a smaller aperture and the quality will start to degrade very much due to diffraction. Microscope lenses/objectives do not have aperture control and always are in the f/1 - f/1.6 range ) . I hope this makes sense . If it doesn't , try shooting with your macro lens at 1:1 and use f5.6 and then f/32 . Then compare the sharpness..
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So what is the best approach?
It depends on the available equipment and magnification one wants to achieve.Here are some options:
1) If we already own a 200mm or a 300mm lens and a 28mm or 50mm , we can try to "stack" / couple them together with a coupling ring. 200mm/50mm will give 4x , 200mm/28mm will give x7 . Retains automatic functions
2) Buy a specialized macro lens for high magnification ( such as Photar/Luminar etc... ) and use it with a bellows (or extension tubes) . This will give the ultimate quality . Easy to achieve up to x20 with a 10-20mm lens . Usually high cost
3) Use a 50mm / 28mm lens reversed on bellows/extension tubes
4) Use a reversed cine lens 12-13mm / 25mm reversed on bellows . Very good quality but it is not easy to know which is a good cine lenses for macro work , plus you have to mount it somehow on a bellows . ( KodakCineEktarII 25mm/f1.9 is awesome )
5) Use a mixture of teleconverters / extension tubes / close up diopters and whatever else there is in house and experiment ! :D
L33t
