Summi Luchs: Good article, but it does not clarify a common misunderstanding of "equivalent aperture", seen in many postings. The article nicely shows the equivalence regarding focal length, DOF, gathered light etc.. But what is frequently misunderstood is that f/1.8 leads to the same exposure time regardless of sensor size for the same scence, light and ISO setting. Some people assume that an "equivalent" aperture of f3.6 (in this example for a f/1.8 MFT vs. full frame) also would lead to a longer exposure and so is not usable in low light. You can extrapolate this from the article, but for beginners it would be nice to add a simple summary that clarifies the practical aspects.
@mosc,I found this a very helpful reply to Summi Luchs's opening comment, which expressed my own view well. Your reply was the missing piece of the jigsaw.My concern with the concept of "equivalent aperture" is that it is too difficult for the unwashed masses and will be misused and misunderstood.
Thomas Kachadurian: The one clarification that is missing is that this does not hold with exposure.
If I expose a photo at f4-1/125-iso400 with my Canon 6D and a 50mm lens, and it is the correct exposure, then make second photo in the exact same conditions f2-1/125-iso400 with my Olympus EM-10 and a 25mm lens the second photo will be 2 f stops over exposed.
Exposure for that scene will be f4-1/125-iso400 with any lens camera combination a Sony RX100II, a Panasonic GH4, A Nikon d7000, a Canon 5D3, or a Hasselblad film camera. Crop factor does not change exposure.
I cannot tell you how many of my students come to me confused about their photos because they read about equivalency on the web and adjusted their exposure accordingly.
The problem is that the prominence being given to "equivalent aperture" in the recent camera reviews is going to be misunderstood.A photo taken at 2.8/100th sec on a small sensor is less likely to have motion blur than a photo taken at 5.6/25th second a larger sensor. But Joe Bloggs will read that the f2.8 small sensor camera has an equivalent aperture of f5.6 and misunderstand.More photos are spoiled by too low a shutter speed than noise and DoF.
konmin: I think having a common benchmark is useful reference for everyone. I do appreciate Richard and his team for writing this article.
Hmm, for crop sensor cameras, I hope camera manufacturers would be upfront about the equivalent aperture values too.
Most do state the equivalent focal lengths (in 35mm terms) but ignores the aperture values.
The reason could be that the aperture values would appear less appealing if camera manufacturers do so e.g. a Panasonic 42.5mm F1.2 OIS on a Four Thirds sensor would be 85mm F2.4 in 35mm terms.
Mark 9473, Absolutely. The unwashed masses who don't read this article, but understand that exposure is determined by F number, shutter speed and ISO, would think "equivalent aperture" applied to the exposure as well as DoF.That is the danger of the equivalence concept, that it will be misunderstood, and wrong buying choices will be made.
Mike Boreham: The primer righty mentions pigment and dye inks as an important factor, but the first group test makes no mention of whether the printers are pigment or dye, and the side-by-side comparisons do not include this factor.
Great thanks very much!
The primer righty mentions pigment and dye inks as an important factor, but the first group test makes no mention of whether the printers are pigment or dye, and the side-by-side comparisons do not include this factor.