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Friday, 03 August 2018


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I'm really tired about the so-called "equivalencies" between full-frame and other formats, especially when people misunderstand them and think that a 35mm APS-C lens is "really" 52mm. No, it isn't! When you get right down to it, every format has its own characteristics. The "equivalencies" are just ways of trying to draw correspondences between them, but these correspondences are always imperfect.

Re the Pentax 50mm lens, I find it kind of interesting that they're now creating insanely huge, heavy, complex normal lenses. Back in the day, manual-focus Takumars always seemed smaller and lighter than comparable lenses from Nikon, Canon, or Minolta.

Of course 1.2 is 1.2, but 25mm is also 25mm and not 50. If you convert, convert everything.

You might also believe that, having the same depth, a bucket with a diameter of 1 foot collects the same amount of water than one with a diameter of 2. No, it wont, it simply wont. The latter will collect 4 times more water. It's basic physics.

Lenses wok the same and a FF 50mm ƒ/1.2 will collect 4 times the light/photons per unit of time than a M43 25mm ƒ/1.2 because it has 4 times the collecting area.

But like I said in that other comment, I don't care. M43 works more than well enough for me with its pros and cons.

I think your reader meant that the depth of field of the 25mm 1.2 is equivalent to a 50mm 2.4.
(I’m not getting mixed up in that, there is so much confusion about that. A video I saw from a big site had in the headline that smaller sensors have less depth of field...)

I love the juxtaposition.

". . . my 20mm ƒ/1.7. Optically it's still one of my favorite lenses, but it's remarkably slow to focus

20 mm, F1.7, 6/7, 55.5x20.5 mm, 55 g.

"...But I'm still really GASsed out supine and stupid by the Olympus lens."

25 mm, f1.2, 19/14, 70x87 mm, 410 g.

"What are we going to talk about when the only lenses anyone uses are in smartphone modules?" - Stop scaring me!

Isn't f/2.8 equivalent to 17 miles an imperial gallon 8-)

From Mike’s post, “Other readers said it is really a wide-angle lens. Nope again, because angle-of-view descriptor words take into account the format of the lens-sensor system for which the lens was designed.“

Yup. And to figure what is a “normal” lens for any format, you go by the diagonal measure. In film cameras 35mm format was about 43mm. 6x6 was approximately 85mm, and using Mike’s example of an 8x10 view camera, a 300mm (or 12”) was normal. Optics are optics and that stuff is all the same no matter what type camera you are talking about.

I agree with Ken Tanaka about not buying very expensive m4/3 lenses. I have used m4/3 for 6.5 years and am still quite happy with it for my purposes. Currently I am using the PEN-F and E-M10II. The Olympus f1.8 and Panasonic f1.7 primes are small, not overly expensive, and very good. That is what I want. I don't want the big, very expensive lenses. If I did want something them I would instead just go ahead and get a FF body (Sony mirrorless, maybe a future Canon/Nikon mirrorless, or DSLR) and get some good primes to go with it.

With regards to your comment on the AF speed of the Panasonic 20mm f1.7, while it is a bit slower than my other 10 or so m4/3 lenses I found while spending time on multiple occasions playing with the Fuji X-Pro2 and X-T2 with the Fuji 23mm f2, Fuji Zeiss Touit 32mm f1.8, Fuji 35mm f1.4, Fuji 35mm f2, Fuji 56mm f1.2 that the 20mm f1.7 on my E-M10II at the same time/place could S-AF as fast as those lenses. I haven't heard much complaining about the S-AF speed of those Fuji primes.

If your life is about depth of field then apertures are equivalent by one rule; if you care primarily about exposure, they're equivalent by a different rule. (And it's often a matter of what your kind of photography gives in abundance vs. what is always in short supply, as much as differing preferences.)

For me, DoF is nearly always something I'm struggling to get more of under dark conditions, and exposure is the real limitation on getting the picture at all, so I care about the f/stop as stated (okay, okay, what I actually care about is the t/stop).

Similarly, when I was growing up, tilt lenses (and tilts on view cameras) were primarily used to give the appearance of much more depth of field than was actually present, to make the pictures people wanted (not just art/landscapes, but product photography). Now, people buy them mostly to "misuse" them to reduce the apparent depth of field.

Certainly limiting DoF to reduce background distractions and help focus attention can be a very useful technique; but it's still the exception in my work.

Isn't if fair to say that DOF of an f/1.2 lens in m43 is equivalent to DOF of an f/2.4 lens in 35mm format?

I dislike the oversized 50 mm lenses. Part of the charm of the fifty is that it can be put on the camera and casually carried around, taking pictures with a setup that's pretty compact and evokes the feeling of SLRs from the 70s while delivering high image quality. But look at that Pentax! I first thought it was a 645 format camera; full frame DSLRs are the new medium format in terms of size.

Since I very much like the 50 and put my money where my mouth is, my carry-anywhere 50 is the Sony 55/1.8, which is very light, focuses fast and renders a pleasant image at any aperture. Granted, it's only f1.8 (on full frame, equivalent to f1.8 as can be read on the Internet), but in this day and age I rarely feel the need for f1.4 since ISO 800 is still fantastic and modern lenses are sharp even at the largest aperture. For more meticulous use, I choose the Voigtländer 65/2, which is bigger, a macro, not 50, has "only" 10 elements and is at the top of the game in terms of performance.

Perhaps this illustrates why you should be writing technical books on photography rather than thrillers. Have you thought about a "best of" book from the blog?

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