150mm 2.0

Started Aug 22, 2013 | Discussions thread
bobn2 Forum Pro • Posts: 51,034
Re: Excellent!

MAubrey wrote:

Great Bustard wrote:

So, the 150 / 2 at f/2.8 resolves 51 lp/mm in the center and 47 lp/mm on the edges, whereas the 300 / 4 at f/5.6 resolves 39 lp/mm in the center and 35 lp/mm on the edges.

Now, when we normalize for sensor size, we have:

  • 150 / 2 at f/2.8: 51 lp/mm x 13 mm/ph = 663 lp/ph (center); 47 lp/mm x 13 mm/ph = 611 lp/ph (edge)
  • 300 / 4 at f/5.6: 39 lp/mm x 24 mm/ph = 936 lp/ph (center); 35 lp/mm x 24 mm/ph = 840 lp/ph (edge)

What you have going for you is that most people here (perhaps even including yourself) do not understand the difference between lp/mm and lp/ph, and what it has to do with the resolution of the photo (Hint: lp/ph is the relevant measure in terms of the photo the lens produces with the camera it was used with).

Ah, but GB...what sensor are they putting the 150mm on? The lenstip data is on a 10MP E-3 sensor. Put it on a contemporary 16MP sensor with a weaker AA filter and you'll see a difference. The best μ43 lenses are hitting 83 lp/mm these days in the center. If this lens is as good as everyone says, we shouldn't expect anything less. So we could likely expect that on an E-M5 or E-M5 that the 150mm f/2 likely be breaking 80 lp/mm = 1040 lp/ph in the center & 977 lp/ph on the edge.

The Canon 300/4 was being tested on a 8MP camera, which has a pixel size the same as a 5DII, so we might expect that the 5DII would indeed produce the kind of resolution calculated above. Anyway, as has been pointed out frequency, the increase of pixel density is a matter of diminishing returns, you don't get full whack as you increase. Photozone has tested some lenses on 10 and 16MP, and they get about a 22% increase, so we might expect this lens to go from 51/47 to 62/57 rather short of your 80. That would be 806/741 lp/ph. The 80 lp/mm sounds optimistic to me. That rating was for a macro lens, and you wouldn't expect a long lens to get close to that.

Anyhow, the discussion has got to the point of diminishing returns, what was being proposed was that the Canon 300/4 was somehow in a different league in terms of image quality (a pretty average lens). The truth is, on the cameras they are designed to work with, they are much of a muchness.

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