View Single Post
  #18  
Old 19th June 2017
drmarkf's Avatar
drmarkf drmarkf is offline
Full member
 
Join Date: Aug 2008
Location: Cambridge, UK
Posts: 4,028
Thanks: 248
Thanked 372 Times in 316 Posts
Likes: 1,295
Liked 940 Times in 527 Posts
Re: Diffraction Testing.

Quote:
Originally Posted by Ricoh View Post
Could 1/15s be the reason, or is that sensor stabilisation so good that it should produce a sharp image in the absence of diffraction.
I certainly considered that, Steve, and there might be an element of shake of course, but I took 13 frames of assorted boats going past there at 15 and 23mm, and f22/ASA64, and the shutter speed varied between 1/15th and 1/20th. This was with the E-M1ii and Panny 12-35, using body IS-Auto. I had focussed roughly in mid-stream and obviously was holding the camera as steady as I could. That image has had some reduction in clarity, structure and contrast selectively over the boat & oarsmen, but nowhere else.

All of the shots look basically the same, but if there is any consistent difference it is between those at 23 and 15mm, with the former looking better in the background (the one I showed is a modest crop of a 23mm one - it's around 90% of the frame width). That would be consistent with diffraction being less at longer focal lengths (I don't know if that's a characteristic of that lens), but you'd expect variation if it was camera shake, and worse at longer FLs, surely?

Certainly, I'm very happy handholding that camera-lens combination at around 17mm at 1/15th in the street in the evening or when I'm after subject blur, and it's something I do all the time. I don't count & measure this sort of thing, but I'd estimate well under 10% of my shots like that would show unacceptable background blur. I regularly handhold in the street at 1/10th, in fact, with both the 12-35 and Panny 15 (ignoring what is possible with the 12-100, of course!).

The next time the opportunity arises I'll test this out a bit more formally, comparing with c.f8 with an ND filter.

I could think of some scenarios where a bit of overall softness would actually look quite good, so it would be good to know for sure.
__________________
Regards,
Mark

------------------------------
http://www.microcontrast.com
Olympus E-M1ii x2: 7-14, 12-100, 17, 40-150, 45, 60, 75, 300, 1.4tc.
Panasonic 12-35, 15. Samyang 7.5 fisheye. Laowa 7.5.
Assorted legacy lenses, plus a Fuji X70.