Notes on practical aspects of using the Nikon D80 DSLR for photomicrography

A hobbyist's personal perspective by David Walker, UK

 

Salient points from tests below on author's Zeiss microscope:

- The Nikon 10 Mpixel D80 seems a competent camera for photomicroscopy if sought as an extra feature to traditional photo work; its lack of lens-off metering and true mirror lock can be worked around, as users have found for the D50.

- The D80's 'exposure delay' mode (shutter release 0.4 sec after mirror up) with a 40x objective does permit vibration free work at 1/250th or at longer than 1/8th sec with tungsten lighting (on author's setup) .

- For 10x objective and lower mags, no evidence of camera vibration seen when using 'exposure delay' with tungsten lighting at normal shutter speeds e.g. 1/250th.

- The D80 is not currently supported by the Nikon Capture / RAW software compatible with the D50/D70/D200 and there's a considerable extra cost for Nikon's new 'Control Pro' software with separate RAW editor 'Capture NX' (ca. $220 for both).

- Buying just the 'Camera Contro Pro' software (ca. $70) keeps cost down if Photoshop Elements 3+ is owned.

- On a Zeiss scope the standard 10x Kpl W eyepiece was a competent projection lens for Zeiss achro and apo objectives with no evidence of undue aberrations in crop area.

- Little if any improvement was spotted in test images taken with the 10 Mpixel D80 cf 6 Mpixel D50; image appraisal e.g. critical focus seems harder with such large images.

 

The Nikon D80 is a 10.2 effective Mpixel DSLR released in 2006 and has received good reviews; it has a typical price of 539 / $925 for the D80 body in UK / US (Jan 2007).

This article assesses from my hobbyist's perspective selected features of the D80 (on loan to me) for photomicroscopy on a Zeiss stand. In particular I was interested to see how it compared to the 6.1 Mpixel Nikon D50 which the author is very familiar with. Fellow microscopy enthusiasts trying other makes and models of DSLRs have also shared their experiences. (See links.)

The two key features not on the D80 cf the D200 of potential interest to the microscopist are a true mirror lock and retaining metering with the lens off. The D80 does have an 'exposure delay mode' where the shutter is triggered 0.4s after the mirror goes up. The Nikon manual notes an example of the potential use of this feature is 'microscope photography'.

Mirror lock on a DSLR (as on SLRs) does not necessarily remove all camera sourced vibrations for photomicroscopy, the shutter can also contribute (e.g. see Ian Walker's experiences with the Canon 350D on a sturdy Zeiss stand). In-camera metering is useful but not vital because the DSLR allows fast assessment of an exposure on the camera's LCD or on a PC screen within a few seconds of capture if software for remote camera control / image transfer software is used.

 

Microscope - camera set-up

The D80 was attached via a third party 35 mm photomicro' adaptor to a vertical monocular tube on the spare top port of a Zeiss Photomicroscope III (shown right). A USB 2.0 cable enables remote control and image transfer to a PC. A Wein SafeSync adaptor was used for flash work with an old SunPak 2400 flash gun when required (sat on field lens below condenser).

A sturdier Zeiss vertical tube is available for 35 mm work, I'm still seeking one, but the present camera attachment may well be similar to that of other hobbyists.

The projection eyepiece was a Zeiss 10x Kpl W eyepiece (on small collar). In the absence of a suitable projection eyepiece, I've previously found that this gives a good flat field essentially aberration free for Zeiss objectives in the crop area of the sensor with a D50 DSLR. Visual / camera focus was matched by using the dioptre setting of the bino head.

This set-up captured 66% of the field that a 35 mm SLR captured. I tried a 4:1 projection eyepiece from Zeiss but found it gave no benefit in field or image quality over the 10x Kpl eyepiece. Some DLSR users (e.g. Ted Clarke and Jan Hinsch, see links) have shown that a 35mm SLR lens of appropriate focal length can be a good match for projection in photomicroscopy; an approach I'm keen to try but isn't practical at present on my set-up because of a lack of a sturdy external camera support or custom coupling.

Despite a good parallax set-up for camera focussing, final critical focussing for such large images was often required by inspecting a sequence of images transferred to the PC while making tiny focus adjustments. The image was viewable on the PC screen after ca. 3 secs for a full res RAW image.

 

 

Interfacing camera with a PC for remote camera control and image transfer

The Nikon D80 is apparently not currently supported by Nikon Capture 4.x software i.e. the camera remote control and RAW editing package that supports the D50 / 70 / 200. Nikon have brought out two new software packages 'Camera Control Pro' for remote control and 'Capture NX' for RAW editing. To buy both these packages is an extra 178 / $220 typical cost in UK/US. (Nikon Capture 4.x wasn't a trivial purchase at 80/$90). There's 30 day free trials of the two packages downloadable from the Nikon website and they offer an upgrade path for Nikon Capture owners.

Only the Camera Control Pro software alone is required if a potential D80 buyer has photoediting software that supports Nikon's RAW files, e.g Photoshop Elements 3+ or CS with Adobe's Camera Raw 3.6 plug-in. Saving captured image files to jpeg avoids the need for RAW support but loses the advantages that RAW offers.

For this review I used the trial Nikon Control Pro software and Photoshop Elements 3 as my PC is next to the microscope. This proximity isn't always practical and images saved to card can be edited later, although for me the almost instant image review and ability to tweak fine focus in particular was an invaluable feature.  

 

Potential oversampling and Image Appraisal

For an excellent discussion of the factors affecting sampling with interactive Java tutorials to show when oversampling may occur, see the links below to the Nikon MicroscopyU website. These tutorials clearly show that capturing an image and retaining detail at the lowest magnifications requires the greatest pixel count (Mpixels) but at the highest mags a quite modest sensor can often suffice for screen images. So for the typical hobbyist like myself using objectives from the lowest to highest power, it's worth being aware of when oversampling occurs and compare captured images with the visual to see whether it's detrimental. My own preference, as I don't require large prints and often just screen images, is to switch to a modest 1.3 Mpixel webcam or even security style camera for image capture with a 40x objective and higher. I find the heavily resized DSLR images less satisfactory at this power and prefer the ease of on-screen 'live view' focus that a better matched sensor gives (see examples below) especially for live organisms.

From a practical standpoint, within a given budget, normal photo requirements such as print size most likely govern the DSLR sensor size so the specs may have been predetermined before the bonus of use for photomicroscopy.

To appraise DSLR images after capture, there's a natural tendency to 'pixel peep' as it has been dubbed i.e. viewing images at 100% on screen. I do it myself, but need to keep in mind that for the typical 100 dpi LCD screen on my PC this is equivalent to viewing a poster sized 'print' on screen of 38 x 26 inch from a close distance so even when focussed they can look soft, especially as 'out of camera' DSLR images tend not to have the same sharpening that the consumer digicams often have.

 

Assessment of the D80 'exposure delay mode' feature for vibration reduction

Every photomicro set-up is of course different, so the results below can only be illustrative for the author's set-up.

The camera vibration with tungsten lighting was assessed using a similar procedure to that suggested by Zeiss in their excellent 'Photomicrography with 35 mm SLR cameras' which is downloadable from their website; i.e. shutter speeds from 1 sec to 1/250 sec captured a sequence of images using the 10x objective and 40x objective. Focus was judged by viewing images at 100% with a reference image taken with electronic flash i.e. where vibration wouldn't be a factor.

The shutter speed windows which gave vibration free results are summarised below.

Objective

Without shutter delay

With shutter delay

10x

 ca. 1/8th or longer

 all speeds

40x

1 sec or longer

1/8 sec or longer and 1/250 or shorter


1/250th tungsten, no exposure delay mode.


1/250th tungsten, exposure delay set. 


1/250th, electronic flash. 


1/250th, no exposure delay mode.


1/250th, exposure delay set. 


1/250th, electronic flash. 

Many of my photomicrography interests are with a 10x objective or lower. I used the D80 camera with tungsten lighting at typically 1/250th with 'exposure delay' with no fear of the camera mirror or shutter causing vibration.

At 40x objective and above, especially where the microscopy technique may demand shutter speeds lower than 1/250th, I would prefer to use flash (as I do on my D50) to ensure vibration free results.

 

Six versus ten megapixels (D80 cf D50)

I had a stab at comparing images near the limit of visual acuity at low mags on the D50 cf the D80 where the extra megapixels of the D80 are most likely to show any benefits. Two test subjects are below.

For the subjects tried, I was struggling to see any marked differences in image detail between the D50 and D80. Camera review sites do show significantly extra line pair resolution for standard test charts and a prime lens in normal photo work for the D80 cf D50 but perhaps may not be evident in most photomicroscopy subjects. I'd be interested to hear suggestions from readers of demanding test subjects for the microscope at the lower mags.

 

Selection of images from the D80

So, enough of the 'pixel peeping'(!), below are a selection of images from the D80. For resizing the huge 10 Mpixel images for the screen, the Photoshop 'WP Pro' plug-in by Fred Miranda was used, with 'low sharpening' set.

 

Comments

If buying a DSLR for normal photography and the Nikon D80 is a contender, from this limited look it certainly seems capable of competent results on a microscope, with neither the lack of true mirror lock nor lens-off metering a serious limitation. The 'exposure delay' feature of the D80 on the author's photomicro' setup gave me confidence to use objectives at 10x and below with tungsten lighting at normal speeds e.g. 1/250th rather than dropping to slow speeds to capture vibration free images. With a 40x objective, 1/250th still gave vibration free images with 'exposure delay'.

The 'killer features' for my own preference of a 6 Mpixel DSLR (a D50) on a microscope rather than a 3 Mpixel consumer digicam (a Sony S75) is not the extra megapixels but the superior low noise performance, the powerful remote camera control with quick image review and the 'big C' - Convenience! The DSLR can be securely and cheaply coupled to a microscope albeit at the expense of the cropping factor with my setup, whereas attaching my Sony S75 consumer digicam was a bodge at best with vignetting. Although many suitable consumer digicams like the Coolpix 9xx series, Sony W7 have been shown by users to work well on a microscope with simple mechanical couplings and often without cropping problems.

My own choice of a Nikon mount model was for the 35 mm film legacy but other DSLR makers offer features on their models that Nikon haven't rapidly taken up on their budget to mid-priced models, notably true mirror lock, lens-off metering, auto sensor dust removal, image stabilisation in camera body and even live preview is offered by some makers now (e.g. Olympus E330, see Ted Clarke's article link below). If considering remote camera control and image transfer, the software required and that for RAW image editing is worth factoring in as it may be a considerable extra cost.

Do you need 10 Mpixels for photomicroscopy? I find my 6.1 Mpixel Nikon D50 is excellent for low to mid power microscopy but overkill much of the time at higher mags and felt the D80 images on a microscope were bigger but not necessarily better. The reason frequently cited for more megapixels is for larger prints or perhaps the option to selectively crop, for which the D80 is an excellent camera if budget permits. But these latest models are currently a big commitment price wise and being the latest sensor have a correspondingly higher depreciation. For the microscopist keen to try a DSLR body, the older 3 - 6 Mpixel models sell very competitively e.g. on eBay for a half to third of the price.

Comments to the author David Walker are welcomed.

 

Acknowledgement: Thank you to a colleague for the extended loan of the Nikon D80 over Christmas / New Year.

Footnote: Initially I did not have full D80 NEF file functionality in Photoshop Elements 3 with Adobe RAW 3.6 plug-in until I discovered from a web search that a plug-in left from running Nikon Capture will conflict if present and should be moved, not just renamed; see this resource). 

 

Selection of links:

Websites reviewing digicams including DSLRs: DPreview, Imaging-Resource, Megapixel.net, Steve's Digicams and Luminous Landscape. The first two include rigorous tests of sensor parameters such as resolution (with lens) and noise.

Micscape articles on DSLR models for photomicroscopy.

Canon 350D on a Zeiss Axiostar assessed by Ian Walker.

Nikon D50 on LOMO Biolam assessed by David Walker.

Nikon D200 assessed by Dan McNeil.

External articles on DSLR models for photomicroscopy.

'Adapting a Canon 300D (Digital Rebel) Camera for Photomicrography Through a LOMO Multiscope Microscope' article by Ken Vernon on www.amateurmicrography.net (follow 'Articles' link).

'"How to" tutorial series: About the use of digital single lens reflex cameras on microscopes' by Jan Hinsch. Modern Microscopy, February 2004. Includes suggestions for mounting a camera and the use of SLR lenses for projection.

'Olympus E330 DSLR for photomicrography with older design microscopes' by Ted Clarke, Microscopy Today, September 2006. Local copy  of article in pdf courtesy Ted Clarke and Microscopy Today Editor. Ted Clarke article includes a description of the use of an Olympus 28 mm f2.8 lens for projection and also describes the benefits of the E330's live preview with magnify mode. Detailed image of Figure 4 from this article here, courtesy of Ted Clarke. (Ted is currently assessing the E330 with a Meiji stereo on a homemade stand, personal communication, see this image of set-up kindly supplied Ted.)

The multi-award winning photomicrographer Charles Krebs shares his set-up and techniques on his website.

The microscopy forums listed on the Micscape Index are an excellent place to read enthusiasts' experiences with various DSLR models as well as discussions on the pros and cons of DSLRs cf consumer digicams for photomicroscopy.

Nikon MicroscopyU website interactive tutorials.

'CCD resolution for optical microscopy'

'Digital camera resolution requirements for optical microscopy'

'Spatial resolution'

(Note that the sensor type in consumer rather than scientific digicams can be another parameter to consider e.g. whether Bayer or Foveon, see this DPreview resource.)

 

 

 

 

Microscopy UK Front Page
Micscape Magazine
Article Library


Microscopy UK or their contributors.

Published in the January 2007 edition of Micscape.

Please report any Web problems or offer general comments to the Micscape Editor .

Micscape is the on-line monthly magazine of the Microscopy UK web site at Microscopy-UK


Onview.net Ltd, Microscopy-UK, and all contributors 1995 onwards. All rights reserved.
Main site is at
www.microscopy-uk.org.uk with full mirror at www.microscopy-uk.net .