Medical / clinical photography
see also:
my examples of clinical photography (warning some blood involved):
Introduction:
medical photography falls into a number of different applications, each requiring a different approach and tools:
close up photos of flat skin lesions, eyes or oropharynx:
an even light source with minimal shadows and minimal catchlight, usually with a single small flash aimed from superior temporal or temporal direction to avoid nasal shadows, and its precise location adjust so as to avoid the catchlight obscuring the pathology.
"By presetting the magnification ratio and then focusing by moving the entire camera assembly, the same magnification for all images is ensured. Scientific validity is compromised if the lens is focused by adjusting its focusing ring because this also changes the image magnification.
When a photograph of both eyes together is needed, use a 1:4 reproduction ratio. This allows the center of the image to be located at the bridge of the patient's nose, with a complete view of both eyes and both temporal orbits. Careful camera work results in a symmetrically composed photograph. Place the plane of sharpest focus at the level of the corneas; again, a small specular reflection provides a reliable indicator for use in focusing. Place the flash directly above the lens to provide symmetrical illumination for both eyes."
high quality macro lens eg. 100mm f/2.8 macro in 35mm terms.
TTL macro flash makes photography much more simple
unlike portrait photography when nice large catchlights are desirable, clinical photography requires small catchlights so they don't obscure detail, and this means a small flash.
a ring flash is acceptable for photography of both eyes such as for strabismus but gives too large a catchlight when used on one eye
generally you will need a small aperture such as f/11-22 to give adequate depth of field although resolution declines with aperture due to diffraction issues.
close up photos of skin textures or lesions that you wish to portray height or depth:
side lighting eg. twin tube macro flash system
high quality macro lens
close up photos of corneas:
ambient light from a slit lamp to demonstrate flourescein staining on corneas (ie. no flash)
LV of 1 thus exposure needed would be approx. 1600ISO, f/5.6 (for DOF) and 1/30thsec
high quality macro lens or IS lens with close focus
The highest magnification generally considered useful for external eye photography assignments is 1:1, ideally a 35mm equiv. focal length of about 100mm with an aperture of f/2.8 for easier focussing and also for easier imaging of dark irises.
camera with relatively low noise at high ISO and with excellent low light AF and effective image stabiliser, whilst being weatherproof to enable easier decontamination as you tend to touch patient's eyelids, tears and potentially transfer to the camera eg. Olympus E3 with ZD 50mm f/2.0 macro and optionally a 1.4x or 2x teleconverter for higher magnification.
high magnification images of corneal lesions may require up to 10:1 magnifications which may be achieved via:
photographic slit lamp biomicroscope with its own highly-collimated flash, to which one attaches a dSLR and an ISO of 200 is most commonly used
dSLR with micro lens but still an issue with lighting and critical focusing.
photography of the full face:
Photography of the full face requires a magnification ratio of 1:10.
"Because this size allows a small area of background to appear in the photograph, carefully choose the background color. To avoid any unusual color casts on the subject resulting from reflected light or from the psychological effects of juxtaposition, a matte finish neutral gray color should be used. If neither a formal photographic studio room nor the space for a roll of seamless background paper is available, one wall of a room in the clinic may be finished with neutral gray paint of between 18-36% reflectance. If space permits, seat the patient several feet in front of the wall to avoid recording any wall texture or sharply defined shadows"
If using available light, camera should have an image stabiliser and easy custom white balance - eg. Olympus E510 or E3 with the ZD 50mm macro lens.
relatively close photos of wounds:
flat ambient light is often the best here as flash often produces unwanted reflections from blood or oozing fluid which prevent visualisation of underlying structures
ambient office lighting typically has an LV of 2.5 (EV 7.5 at ISO 100) => 1600ISO, f/5.6 at 1/60-125th
high quality macro lens or lens capable of image size down to ~10x15cm
preferably an image stabiliser as may need small lens aperture for adequate depth of field
If using available light, camera should have an image stabiliser and easy custom white balance - eg. Olympus E510 or E3 with the ZD 50mm macro lens.
digital imaging of legacy Xray films on screens:
electronic flash is of no benefit thus a camera with an image stabiliser shooting at ISO100 for max. dynamic range to ensure adequate tonal rendition of important shadow detail (a 14 bit sensor would be even better)
live preview may not work for imaging Xrays on a screen lit by flourescent lighting as the horizontal banding artefact makes it near impossible to use. I suspect this may be an issue for other older technology flourescent lighting situations but new flourescent bulbs do not seem to be an issue.
camera should have an image stabiliser and easy custom white balance - eg. Olympus E510 or E3 with the ZD 50mm macro lens.
procedural work:
as these are usually in a sterile field, camera needs to be able to take steady shots from a distance of 1-3m, preferably without distracting flashes or need to use tripods.
to ensure the best timing, a burst mode of 10fps is ideal
thus a camera with low noise at high ISO with image stabiliser and easy custom white balance
eg. Olympus E510 or E3 with the ZD 50mm macro lens.
the ability to mount the camera above the scene and control it remotely by WiFi can be very useful
eg. Canon 1D Mark III with 70-200mm L series f/4 or f/2.8 IS lens + WiFi attachment + mounting stand
special purpose UV and IR work:
UV and IR photography is often used for forensics
ideally the camera should be one without the usual IR blocking filter and with a live preview for composition and focus
IR can be used to demonstrate subcutaneous veins
eg. Fuji S3 Pro UV/IR camera with Nikon UV/IR lenses
eg. modified Olympus E510
general documentary work:
wide angle zoom lens to capture the staff &/or patient in their environment
use at conferences:
cameras can be an important tool as an aid memoir to record visual presentation materials efficiently as well as a tool for networking and promotion
image stabiliser makes life easier and a reasonable short telephoto focal length
whilst the Olympus E510 or E3 with the ZD 50mm lens is fine, they are a little noisy in this environment, so this is one situation where a non-dSLR such as the Canon G9 would come in handy as it can be set to a relatively silent shutter.
digital imaging of ECG's and other documentation instead of using a scanner:
an A4 size 12 lead ECG recording can be imaged as follows:
scanner at 75dpi for computer display
scanner at 300dpi for re-printing
10 mpixel camera will give just over 300dpi at full resolution of an A4 sheet
setting the E510 to SQ jpeg at 1024x768 gives a good size for computer display while keeping file size low (200kb at 1/8 compression) and results in just under 90dpi for an A4 sheet.
Equipment options:
Beginners kit:
Olympus E510 with kit lens
this is capable of taking very reasonable shots of most clinical situations in available light and has the option of built-in flash if really needed.
strongly consider a ZD 50mm macro lens.
Advanced kit:
Olympus E3 with 12-60mm SWD lens for best AF in low light
strongly consider a ZD 50mm macro lens and perhaps an Olympus ring flash
this is a great compromise on capability, weather-proofing, size, weight and cost with a 3-5EV image stabiliser in the body.
My preference is a hybrid model utilising the strengths of each digital format:
Olympus kit for most work including ultra-wide angle and macro:
Olympus has image stabilised body which:
when combined with the 7-14mm lens allows hand-held ultra-wide photos of people working while allowing slow shutter speed to blur their faces
even the 14-42mm ED kit lens works very well hand held for the vast majority of clinical shots including Xrays mounted on a viewing box and ECG's using office lighting and is capable of reasonable close up shots of hands.
its f/5.6 wide aperture at the telephoto end will limit available light shots of procedures though where subject is moving - may need to resort to flash with this combination.
the ZD 50mm macro lens allows even sharper images and its f/2.0 aperture is of use in low light and doubles nicely as a portrait lens.
the wider depth of field and much lighter camera allows hand held macro flash photography while the image stabilised live preview makes manual focus of macro subjects much easier when hand held.
it has a MUCH more easy custom white balance procedure than the Canon - and given the frequent use in ambient lighting - usually of different fluorescent lights, this is VERY useful.
I initially considered the Canon 1D Mark III but it's just too big & heavy to take to a hospital environment each day.