Archive for May 2013
A new release of the Instant Guide to DSLR Dashboard is available for your reading pleasure. In addition to minor tweaks and improvements, this version of the guide includes information on setting up wireless tethering and using Raspberry Pi as a DSLR Dashboard server.
If you’ve already purchased Instant Guide to DSLR Dashboard, you can download the new version as described in the guide.
Our garden residents provide ample opportunities to make use of my Tamron SP 300mm f/5.6 Adaptall 2 lens mounted on a Canon EOS 1100D. Most of the time, I have to shoot through the thick double-layer glass of a terrace door, but I managed to capture this photo through an open window on the second floor of our apartment. This is, by the way, our blackbird named Haru. These days, he is busy feasting on apples we put for him and his lady (more about her in another post) and patrolling his territory, a.k.a. our garden.
Sunday wasn’t a very good day for him, though. After he took a bath in a plastic tray we put for that purpose, the poor bugger flew right into the glass terrace door. He hid then in a corner of the garden, and sat there for a while slightly confused. He is alright now, dashing around the garden and looking busy as usual.
Taken with Canon EOS 1100D and Tamron SP 300mm f/5.6 Adaptall 2. Processed in digiKam. Shutter speed: 1/250 sec. Aperture: f/5.6 ISO: 400
The Sharpen tool in digiKam offers three sharpening methods: simple sharp, unsharp mask, and refocus. Each method has its advantages and drawbacks. The simple sharp technique uses a standard convolution matrix algorithm to improve image details. If you are curious about the nitty-gritty of the convolution matrix, the GIMP documentation provides a brief description of the algorithm. In fact, the simple sharp tool in digiKam is ported from the GIMP project. The main advantage of the simple sharp method is its simplicity. The Simple Sharp tool in digiKam has only one adjustable parameter called Sharpness which determines the strength of the applied sharpening filter. On the downside, the simple sharp method doesn’t handle image noise very well: it tends to introduce more noise in photos taken at lower ISO settings.
Unsharp mask is a popular sharpening method which sharpens the edges of the elements without increasing noise. The unsharp mask technique creates a slightly blurred version of an image, which is then subtracted from the original in order to detect edges. The resulting mask is then used to increase contrast along the detected edges to produce a sharper final image. The Unsharp Mask tool in digiKam has three adjustable parameters:
Radius specifies how many pixels on either side of an edge will be affected by sharpening. High-resolution photos allow higher radius.
Amount determines the strength of sharpening.
Threshold specifies the minimum difference in pixels that indicates an edge where sharpen must be applied. This lets you protect areas of smooth tonal transition from sharpening, and avoid creating blemishes in face, sky or water surfaces. 
When using the unsharp mask tool, you should keep in mind that it can introduce subtle color shifts and halo artifacts visible as dark or light outlines near edges.
Finally, the Refocus method is based on the Refocus plugin for GIMP which uses a technique called FIR Wiener filtering to sharpen the image (see http://en.wikipedia.org/wiki/Wiener_filter). Similar to the original plugin, the Refocus tool in digiKam offers several adjustable parameters:
Circular sharpness is a key parameter which determines the radius of the circular convolution. Basically, it specifies the strength of the refocusing action.
Correlation helps to reduce artifacts. Increasing the correlation value reduces the sharpening effect. Useful values are 0.5 and values close to 1 (e.g., 0.95 and 0.99).
Noise filter may help to reduce artifacts. Similar to the Correlation parameter, increasing the noise filter value reduces the sharpening effect. A useful value is 0.01.
Gaussian sharpness is used to specify the radius of the Gaussian convolution for correcting Gaussian blur. In most cases, it should be set to 0, as it introduces artifacts. When using non-zero values with Gaussian sharpness, you might need to increase the Correlation and Noise filter parameters, too.
Matrix size determines the size of the transformation matrix. Increasing this parameter may give better results, especially when large values are chosen for the Circular sharpness or Gaussian sharpness parameters. In most cases, you should select a value in the range 3-10. 
Refocus is the most powerful and effective sharpening tool in digiKam’s arsenal, as it not only offers a superior sharpening method and granular controls, but can also handle noise.
 Source: http://refocus.sourceforge.net/
It all started with a Tamron 70-150mm f/3.8 CZ-715 Adaptall lens I got thrown in as a freebie when I bought my Nikon F-301. Although I had a vague idea of the Adaptall technology, I knew nothing about this particular lens. While doing research on the lens, I discovered that Tamron had a strong product line of the SP series Adaptall 2 lenses targeted at serious amateurs and professional photographers. One lens, in particular, piqued my interest: Tamron SP 300mm f/5.6 Adaptall 2 54B. While this model is a bit slow, it has an impressive 300mm focal length and features 1:3.3 macro capabilities. More importantly, the lens is rather inexpensive, and I’ve managed to find a unit in excellent condition at a very reasonable price on a local online auction.
Tamron also produced a 2x converter for use with Adaptall 2 lenses, and I was lucky to find one on eBay. This converter doubles the focal length, but it does so at the expense of the aperture. So the converter transforms a Tamron SP 300mm f/5.6 into a 600mm lens with the maximum aperture of f/11. Tamron lenses with the Adaptall 2 adapter for Nikon F mount are compatible with Nikon’s analog and digital SLRs. When bolted onto a Nikon DSLR with a DX sensor, the lens’ focal length equals 450mm. Add the 2x tele converter, and you get an whopping 900mm focal length.
To test the lens, I went to our local botanical garden. I started with my Nikon F-501 film SLR loaded with Fujifilm Fujicolor C200.
I also tried the lens with my trusty Nikon D90 DSLR. Using Tamron Adaptall lenses on a modern DSLR is only possible in the Manual mode. The camera can’t read aperture values either, and you have to switch to manual focusing. In other words, shooting with the Tamron SP 300mm f/5.6 Adaptall 2 lens is a full-manual affair. On the positive side, focus confirmation seemed to work just fine.
So how did the lens perform? For its age, the lens did admirably well. Sharpness is good, and the lens produces pleasing and creamy bokeh. Overall, it’s not so shabby for a twenty-something-year old lens, especially considering the price.
By the way, if you are looking for information about Tamron’s Adaptall lenses, the Adaptall-2.org website got you covered.