Ever wonder what the f-number of your eyes are? It can easily be calculated using the human eye’s focal length (~22mm) and physical aperture size. Here’s what Wikipedia has to say:
Computing the f-number of the human eye involves computing the physical aperture and focal length of the eye. The pupil can be as large as 6–7 mm wide open, which translates into the maximum physical aperture.
The f-number of the human eye varies from about f/8.3 in a very brightly lit place to about f/2.1 in the dark. The presented maximum f-number has been questioned, as it seems to only match the focal length that assumes outgoing light rays. According to the incoming rays of light (what we actually see), the focal length of the eye is a bit longer, resulting in minimum f-number of f/3.2.
The article also notes that the eye cannot be considered an ordinary air-filled camera since it’s filled with light refracting liquid.
Matthew Gore of Light & Matter created this beginner-friendly video tutorial on the three basic elements of exposure: aperture, shutter speed, and ISO. It’s explained with easy to understand illustrations and examples, and features graphics and sounds that are reminiscent of old 8-bit video games. You can also find a text-based version of the tutorial here.
Even if you have a good command of using f-stop numbers and properly exposing photographs, you might not understand the math behind why f-stop numbers are what they are. Here’s a simple (albeit math-filled) explanation by Dylan Bennett of what f-stop is, including a simple trick you can use to memorize the f-stop scale.
You probably know that stopping down (i.e. increasing your f-stop number) can increase the sharpness of your subject, but how much should you stop down to boost resolution without losing that nice, creamy bokeh? Roger Cicala did some research on this question and writes:
For those lenses that do benefit, stopping down just to f/2.0 provides the majority of resolution improvement. The difference between wide open and f/2.0 is generally much greater than the difference between f/2.0 and the maximum resolution.
Getting the edges and corners sharp requires stopping down to at least f/4 for most wide-aperture primes, and some really need f/5.6. Stopping down to f/2.8 may maximize center sharpness but often makes only a slight difference in the corners, at least on a full-frame camera.
None of the lenses performed any better after f/5.6 (for the center) or f/8 for the corners. Most were clearly getting softer at f/11.
If you’re using a wide-aperture lens, stopping down to just f/2.0 will reap big gains in sharpness while still keeping the depth-of-field narrow. Furthermore, for some lenses you don’t really even need to worry about stopping down for sharpness, since it hasn’t a relatively negligible effect on the outcome.
Modern DSLR lenses don’t usually have aperture rings, and opening and closing the aperture is the camera’s responsibility. If for some reason you need to keep the aperture blades locked in a certain position, the “lens twist trick” can help you do so. Simply untwist the lens from the camera while holding the depth of field preview button.
One practical use for this trick is time-lapse photography. Cameras don’t always close the aperture to exactly the same size every shot, and the slight variation can cause a flicker in the resulting time-lapse video (a problem called “aperture flicker“).
Canon’s new 1D X is an impressive fusion of the old 1D and 1Ds lines, boasting state of the art sensor quality combined with impressive speed, but there’s one downside that may be a big disappointment to some photographers: the camera loses autofocus when used with lenses with a max aperture of f/8.
While there aren’t any Canon lenses that naturally have an f/8 maximum, adding a 1.4x extender to a f/5.6 lens or a 2x extender to a f/4 lens results in a lens with a max of f/8. If you’re planning on upgrading to a 1D X but need extended reach (e.g. you do bird photography), you may need to shell out some extra cash for a faster lens.
Instructables user art.makes has a tutorial on how you can make a pair of paper iris glasses with adjustable apertures. You could definitely build upon the idea to make each side more like a camera lens (e.g. adding barrels, f-stop values) — perhaps as part of a geeky Halloween costume? Read more…
Based on a recently published patent filing, Canon appears to be working on putting aperture rings on EF-mount lenses to allow the aperture to be smoothly controlled during video recording. The patent, filed by the company back in March and published late last week, talks of a “diaphragm driving unit” and shows a third ring on the lens in addition to the zoom and focus rings.
As many of you know, Canon is planning a “historic” announcement in Hollywood on November 3rd. Many people are guessing that an EF-mount camcorder will be announced, while others are hoping for a Canon 5D Mark III that’s even more geared towards filmmakers. This new patent is further proof that Canon is indeed planning big things for the filmmaking market.
Tina Roth Eisenberg, AKA swissmiss, has just launched an online temporary tattoo store called Tattly. Of the small selection currently offered, two of them are designed for photo geeks: Aperture and Instant Camera. You can pick up a pair of either tatt for $5 with free shipping in the US. Hopefully the prices will come down a bit if the store becomes popular.
Bryce Bell of cardnetics created this business card design that features a built-in aperture mechanism. Pull the lever down and the aperture opens up. If you run a photography-related business, this could be a neat business card to pass out to your clients. Pre-assembled cards start at $6 each, while you can buy kits that you put together yourself for $2.50. If you want to try printing and laser cutting the card yourself, the design templates are available here.