As will be apparent to anyone reading this blog, bird photography is a Thing for me. This is an activity ordinarily pursued with a long lens; my usual setup totals about 5 pounds, or another half pound if I add a teleconverter. I'm used to toting it, but it does get heavy after a while, and I might not want to pack it if I were going on a trip that wasn't targeted at birding. So, I was interested in finding a possible alternate optic that might be usable even if not quite as good. I was intrigued to find that I could buy a used Canon 70-300 DO lens in excellent condition for less than $350 USD. This lens is notably shorter than others in its focal length range, thanks to its use of Diffractive Optics (DO) technology. It was expensive when it was introduced in 2004, and opinions about its sharpness and contrast for an expensive lens have been mixed
In 2004, digital camera technology wasn't nearly as advanced as it was today. A 6 or 8 megapixel sensor was competitive in consumer-grade DSLRs, which limited the number of pixels that could be cropped away to frame a small subject without visibly diminishing resolution. Sensors were also less capable of operating at high ISOs without becoming excessively noisy. Since bird photography often requires fast shutter speeds, high ISO usage is often necessary.
Today's sensors are much larger and can reach into higher ISO territory before becoming intolerably noisy. Digital post-processing technology provides impressive denoising capability, and AI software products like Topaz Photo AI can often extract or reconstruct image detail that's otherwise lost to the naked eye. One relies on the AI to derive and reflect detail that's actually present in the scene being photographed rather than hallucinating artifacts that aren't, but that's a larger question that I won't attempt to reconcile here. Rather than considering the output from a camera as necessarily comprising an end result in itself, it can now be provided as the input to constructive post-processing. The test of a camera and lens combination, therefore, need not be the appearance of the photos that it outputs directly, but rather whether the information contained in them (most likely, in their RAW files) is sufficient and suitable as a basis to create even better results digitally.
When I looked at a trial image taken with the DO lens (significantly cropped, as most of my bird photos are), it seemed rather noisy as it came from the camera, but exposure at ISO 3200 on a dim day could explain at least some of that.
More broadly, I wasn't seeing as much detail in the bird and its surroundings as I'd like for my collection.
Sharpening and denoising in Darktable provided some improvement in another version.
I still hoped for better, though, and thought that the Topaz software provided an impressive result.
I think the DO lens will be a useful complement to my current setup, but would probably have been disappointed if I weren't able to apply post-processing technology to the images it collects.