In relation to actual shooting and everyday use, we all pretty much know what manipulation of an f-stop does. For example, a 200mm lens with an iris opening width of 50mm would be expressed as an aperture of 200/50 = 4, therefore having an f-stop of f/4. The f-stop is measured by a simple equation then which is focal length over diameter of the (current) lens opening. The ratio is of the focal length to the lens’ aperture. It’s expressed as a ratio, hence on your camera you’ll often see it expressed as 1:1.4 or something of the sort. It is the f-stop that give us a definitive standard say on how wide the aperture is – aka how wide open the iris created by the lens blades is. Yes, some of you will be more than versed in the information to follow, but without a doubt, there are lots of photographers who make their living as such who have little-to-no real understanding of this.Īperture is measured via f-stops. To really understand how this works, it’s beneficial to understand a bit more about F-stops and T-Stops, from the ground up. Also worth noting is that price is not necessarily a good indicator of how close a lens’ aperture will match the T numbers. That actual number, 1.7, is the T-Stop, and some lenses, typically cinema lenses, will be rated as such. So while, for example, a lens’ aperture may be open to 1.4, the actual measure of light hitting the sensor may, in fact, be equivalent to 1.7. For those of you who want a very short and summarized version, the video really simply states that while an F Number may suggest how much light may pass through the lens, it’s not entirely an accurate measure of how much really gets all the way through to the sensor due to light absorbance and reflection etc. It would seem prudent, however, to stand on the back of this, and take it a bit further. The video is very good and gives a basic overview of what F-Stops and T-Stops are, explaining the basics of their function and how they are measured. It’s about the relationship between F-Stops and T-Stops, and as you can all imagine, anything mentioning an F-Stop is enough to get photographers to re-adjust their glasses. Recently a video by Matt Granger has been moving between photographic sites and working its way into conversation like a politician works a room.
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