Ok, pulling something from another thread...there was a discussion about whether or not sensor format (FF vs APS-C) has an effect on the size of the out-of-focus highlights that are rendered by a lens.
from
https://www.pentaxforums.com/forums/872694-post32.html Originally posted by blende8 This is not correct.
Below is a quick comparison between the DA16-50@50 and the FA50/1.4 (both at f2.8):
Same scene, tripod, focussed on something in the foreground, observed the circle in the background.
Originally I noted it first with the DA70, but other DAs show this, too.
Interestingly the DA55 does not show it. This lens covers FF.
After seeing this, I was very curious why that would occur because I am quite certain that the sensor format that a lens is made for has no effect on OOF highlights. A 50mm F1.4 made for FF will create the same size OOF highlights as a 50mm F1.4 made for APS-C, but the only made for FF will be able to create those same size circles over more area. That is my understanding, so I did a few tests of my own tonight.
Basically had my camera on a tripod a certain distance away from a subject, and had bright lights in the background for OOF highlights. Neither the camera position nor scene arrangement changed at all when comparing similar focal lengths in this test. The setup for my 50mm tests is seen here.
Now, I tested 4 different lenses at 50mm: DA 16-50/2.8, A50/1.2, F50/1.7, and FA50/2.8 Macro. I made shots with each of them at f/2.8 and f/5.6.
Here are the f/2.8 shots, in the order of the lenses listed above:
Now the f/5.6 shots.
There are a few interesting things to note here.
1. Assuming that my 50mm primes are indeed very close to true 50mm focal length, the DA 16-50 does not actually reach all the way to 50mm. I had the lens zoomed as far as it would go, but the field of view was significantly wider than with all the 50mm primes. This leads me to believe that the DA16-50 is more like 45mm on the long end (at least when relatively close focused), and Pentax decided to boost it for marketing.
2. The OOF highlights that the DA 16-50mm renders when set to 50mm are indeed smaller than the primes lenses (although not as much as Weiland seemed to indicate). HOWEVER, realizing the fact that the DA is actually a shorter focal length than the 50mm primes, it is clear that the DA will produce smaller OOF highlights because of the wider field of view. It is not because the DA is a lens made for APS-C. If the DA truly matched the focal length of the 50mm primes, then the OOF highlights would be roughly the same size.
I also did a comparison at 28mm with the DA16-50 against an F28/2.8.
f/2.8
f/5.6
Not much difference. I didn't quite seem to match the FOV perfectly with the zoom, but the OOF highlights are very close to the same size. Had I zoomed in just a tad bit more to match the field of view of the 28mm, they would be even closer in size.
And one more. DA50-135 vs K85/1.8 vs M85/2. All at f/2.8.
Again, the APS-C lens output is basically the same as the FF lenses. The APS-C actually has very slightly larger OOF highlights in this one because I zoomed just a hair too far and the FOV is slightly tighter.
Anyways, my point is that the format that a lens is created for does not have any impact on the size of the OOF highlight circles.