Archived posting to the Leica Users Group, 2014/02/21
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]> ... the reality is that focusing at shooting aperture is just not as > discriminating as wide > open focusing. ... Exactly. So, one of the first things I did was set up a system that allowed me to easily focus the Sony and it's 35mm FE at f2.8. The result was images at f8 that were not critically sharp. As I've said before, the a7r is far from a perfect camera. That said, I've also found that the focus magnifier makes a huge difference. It does seem to allow stopped down focus viable. One of the things I miss with the 35mm FE optic is a mechanical infinity focus stop (can't have one when it varies with f-stop). With my dual or multiple focus stacking workflow, it's simplest to take one shot at close distance and immediately move the lens to the infinity stop. With the Sony a7r I have had to find where f 5.6 - 11 is at it's best by using the focus distance scale that is in the viewfinder. It's not quite as easy, but it works. It seems to be just off the left edge of when the infinity symbol appears in the viewfinder. > > First time ( in all the A7r reviews I have read) that I have heard of > this.... > The reviews usually never get into this kind of detail. So, for a fanatic like me, it's always a bit of a crap shoot buying equipment. (B&H must get very tired of me returning equipment that was over-hyped in reviews.) I really do try to wring as much out of the hardware as I can for my very particular type of photography. With the B&W dyes on metallic paper medium that is among my favorite now, even the a7r cannot achieve what is needed for a 17 by 24 inch panorama without multi-frame stitching. The edges are not good enough with the 35mm FE optic and a single frame. So, if the viewfinder with the 35mm on the camera shows me a good 2x1 pan framing, I whip out the Leica 75mm and do a multi-frame stitch job. I might add that with the "rule of thirds" grid lines in the viewfinder, I can easily pre-visualize the 75mm frame as well as the 2x1 stitch job that the 75mm can do. And talk about lack of critical reviews, have you ever heard the medium format digital people talk about ray angle and its affect on edge sharpness? Do they have some magic that has eluded the top 35mm manufacturers? As the a7r v. M240 MTF50 test results I noted in a previous post make obvious, the MP count by itself is irrelevant for the edges. The ray angle and quality of micro-lenses on the chip are huge factors off axis. Zeiss seems to be the leader in the ray angle reduction, and Leica seems to be the leader in the micro-lens department. Paul www.PaulRoark.com > > Is this also true with the A7 (plain old 24MP camera)? > > > Frank Filippone > Red735i at verizon.net > > The Sony a7r focuses at approximately the the f-stop it is set at; it opens > what looks like maybe a half stop more than the shooting aperture. You can > look at the front of the camera and see the iris opening just a bit when > it's focusing. It does not open all the way to wide open (f/2.8 for the > 35mm FE) for easier focusing and brighter viewing. > > So, the a7r is unlike any modern SLR I am aware of. The typical SLR stays > wide open for viewing and focusing, and then stops down for the shot. With > an electronic viewfinder, the viewfinder is just as bright no matter how > closed down the iris is, as long as the exposure (iris, shutter and ISO) is > on the mark. As such, half the reason to have the iris open (viewing) is > eliminated. The other reason SLRs have the iris open when focusing is to > have the DOF very shallow, so it's easier to focus. However, this raises > the issue of focus shifting when the iris shuts down. Sony gave Zeiss one > more variable to forget about (relatively). Since the focusing is being > done at close to the shooting aperture, Zeiss is free to allow focus > shifting as needed to meet other design parameters. > > This is another example of the extent to which the optics and electronics > are being designed as a package. So, one irony of the Sony is that while > it's able to use legacy glass, it is also going to have optics that are > more > tied to the camera than in the past. As such, I think Zeiss will be able > to > produce sharper lenses for less money than could be done when they had to > worry about focus shift issues. > > Note that there is an interesting possible future solution to the vibration > -- have the iris do it all. It can be both iris and leaf shutter. Some > compact cameras do this. However, you'd lose legacy glass compatibility > and > some very high speeds. I would not be surprised to see some lenses with a > leaf shutter option. They are the smoothest shutters. > > Paul > www.PaulRoark.com > > > On Thu, Feb 20, 2014 at 10:19 PM, Frank Filippone > <red735i at verizon.net>wrote: > > > Paul says it does stop down before it AF, Sonny says it stays open > > during AF... Specifically with the same 35mm FE lens > > > > ???? I am confused..... > > > > Frank Filippone > > Red735i at verizon.net > > > > > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information >