Jump to content
UltravioletPhotography

A sneak view of the gear for UV macro work


nfoto

Recommended Posts

I'm posting a few snapshots of the gear currently used for taking true macro (> 1:1) shots of flowers. The set up is at an early stage of experimentation thus what you see is a moving target, but anyway here it is.

 

The flower is set in a small metal (aluminium) cube in which a hole is drilled to act as a water reservoir. This is required so the flower won't wilt immediately after being blasted with my studio flashes. The Al block concurrently functions as a cooler to prevent overheating of the flower. Later I consider adding cooling fins to the block.

 

Here is a tiny Lysimachia punctata ready to be blasted into UV oblivion by my powerful Broncolor studio flashes (each with uncoated Xenon tube and 600 W/s output). I made a make-shift platform by pulling a part of one of my Nikon Multiphot photomacrographic stands and added an X-Y rotating microscope stage to get 3-D movement control. Quite crude and likely needs to be much improved later. I'm currently looking into focusing blocks with micrometer adjustments.

 

heavy_metal_U1408232916.jpg

 

As evident from the picture, the flash reflectors are very wide. I found by trial and error this kind of reflector is much more efficient than the usual more narrow reflector (used with umbrellas and softboxes). The least efficient of all is the 'bare bulb' method recommended by earlier authorities on photomacrography (H.L. Gibson of Kodak fame to name one). To add to the spatial dispersion of light I also added a large Al foil reflector in the immediate background.You have to be careful to avoid light hitting the front of the lens so either use a short lens shade, or carefully arrange the reflectors so light spilled onto the front of the lens is reduced to a minimum.

 

By trial and [much] error I have come up with three lenses that can be pressed into service for the UV macro work. None of them are perfect for this area of photography and I will continue the quest to find even better candidate lenses. However, for now I can make do with this (non-)dynamic trio.

 

First out is the Olympus 38 mm f/2.8 OM Macro lens, made many years ago for the OM system of SLRs. An unusual feature is that the lens comes in its own focusing mount and has automatic aperture operation (however, only functional on an Olympus body). I decided to 'ruggedise' the lens after seeing how it fared in the field. To this end the Olympus mount was replaced with an 'F' mount, the exterior of the lens was covered in a rubber sheath, and I added a front protector that at the same time acted as a lens shade and a mounting foundation for a Nikon SB-21 ring flash (this is a strictly visible/IR flash, but I also perform ordinary shooting with the lens). A metal cap for the front rounded off the proactive measures.

 

Olympus38_U1408252926.jpg

 

Set up in this manner, the Olympus 38 mm covers the range 1.8 to 3 X magnification. Any bigger and the amount of extension to add tends to be impractical (do remember I strive for a field-proven item able to withstand real-life conditions).

 

The Olympus has a customised CPU implanted and the same apply for the two extension rings seen in the background (for the next two lenses to be discussed later). I make a dedicated tube for each and every non-CPU lens so I can keep track of all actual technical settings for each photograph. Thus, with the CPU for the Olympus, any Nikon firmly believes there exists a 38 mm lens with aperture range 2.8-22, operating in 'G' mode, and thus any setting done on the lens can be recorded to the EXIF header of the files. I'm never going to spill the beans and disclose the truth to my trusting Nikons..

 

The front end of the 38 mm is safely ensconced within a robust C-mount adapter lifted from an F-C adapter and further the retaining ring for the optional SB-21 flash.This lens thus fortified has survived many a drop in the field over the years.

 

Olympus38_front_viewU1408252929.jpg

 

For the rear end, I attached a stray light guard pulled off an M2 extension ring. I purchased a stack of these rings as they are very robustly constructed, plentiful and cheap. Not all lens combinations require this efficient shade, but the Olympus certainly does.

 

The UV/IR filtration is either inside the camera (D3200, D5300), or done through a rear-mounted filter box. My unit is provided by the German company Teleskop-Service. It has easily exchangeable filter holders. As the box is designed for astrophotography, it is based upon their special 48 mm filter standard, and has 42 mm female threads at either end. The holders accept directly the 2" Baader series, or the smaller 1.25" series by an insert. You can also use 50x50 filters which fit snugly inside the holder and is held in position by a 46-48 mm step ring acting as a spacer.

 

Filter_box_U1408252931.jpg

 

Filter_holders_U1408252934.jpg

 

I added 42-52 and 52-42 mm step rings, respectively, to the front and rear of the filter box. That allows easy on-the-fly adaptations making connections to 42/39 mm, m43, or Nikon 'F' mounts. Thus the filter box doubles as an extension tube as well and provides linkage between different optical components.

 

The other two UV candidates are Canon 20 m mf/3.5 and the Macro-Nikkor 35 mm f/4.5 lenses. They are far from perfect, even more so than the Olympus 38 mm. The Nikkor is much more responsive to UV than the Canon and also quite a bit sharper, but does show significant spherical and axial colour abberration. The Canon is softer, less willing to pass UV, but at the same time exhibits less direct abberrations. A tough choice indeed.

 

Macro_lenses_U1408252935.jpg

 

These two attach through RMS threads (affectionately and a little ironically nick-named 'Royal Screw'. Hint: The Society is British). Thus you need the proper adapters as well to attach these minute lens heads. I'm fortunate enough to have several BR-15 adapters at my disposal, some of which have undergone further modifications of course). However, RMS adapters can be purchased on eBay these days, so the outlooks aren't that bleak in case you just happen to stumble over a suitable lens.

 

Here is the Canon 20 mm f/3.5 in its field-orientated configuration, ready to do 10X work. You can remove the M2 in front and replace the rear M2 with say a PK-11 (with CPU of course) to get to 5X instead. However, the 5-10X range clearly is not within the comfort zone for the Canon, but a balance has to be struck between performance and practicality.

 

The Macro-Nikkor likes being outside its designated working range (8-15X) even less than the Canon, thus requires more extension, and is not practical to use in the field. I only use it in my studio.

 

Canon20f3,5_U1408252936.jpg

Link to comment

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
×
×
  • Create New...