C-Sonnar Question

[Huck Finn]

I'm confused from reading descriptions of focus shift with this lens - as it applies wide open at the MFD.

I've read that it "front focuses" - which I take to mean that that everything toward the front of the subject will be in focus but that everything behind the focus point will be blurred.

I've read that the DOF is asymmetrical so that the point of sharpest focus is toward the front of the DOF with the in focus DOF extending behind it. Thus, if you focus on the eye, for example, the nose will be OOF.

So, which is it? Is the area of sharpness in front of the point of focus or behind it?

Thanks in advance for your reply.

 

[ferider]

Hi there,

the f2.8 optimized lens front-focuses by about 6cm wide open and at MFD. I.e. focus plane will be at 94cm from the camera, while the camera thinks it is at 100.

Like this:

The f1.5 optimized lens always back focuses (behind the subject) at f2 and above.

Roland.

 

[Huck Finn]

Hi, Roland -

How are you? It's been a while. This lens is tempting me once again.

Thanks for the description. I see why it's confusing. Front focus or back focus depends on the optimization.

So, if I'm not mistaken, if I focus the f/2.8 lens on the eyes at MFD wide open, I'll get the nose focused clearly but maybe not the eyes & definitely not the ear. So, I'd be best advised to focus on the ear?

When Roger Hicks recommends rocking back 2 or 3 inches after setting focus, he must be talking about a lens optimized at f/1/5?

Thanks again.

 

[ferider]

Hi Huck,

that's right. When your lens is optimized for f2.8, and you focus on the eye at MFD wide open, you have to lean in 2-3 inches. Here is an ugly mugshot (cropped) that shows it:

Bottom is what comes out without correction. Top is when you lean in.

Good to read from you here; hope all is well.

Roland.

 

[mfogiel]

Please, look here:

http://www.rangefinderforum.com/forums/showthread.php?t=51742&highlight=comparative+focus+sonnar

and here:

http://www.flickr.com/photos/59177039@N00/sets/72157602216140269/show/

turn on the info while looking at the slideshow.

 

[Huck Finn]

Please, look here:

http://www.rangefinderforum.com/forums/showthread.php?t=51742&highlight=comparative+focus+sonnar

and here:

http://www.flickr.com/photos/59177039@N00/sets/72157602216140269/show/

turn on the info while looking at the slideshow.

Hi, Roland -

These have been extraordinarily helpful - especially the 2nd one. I remember reading the old thread when it was created a couple of years ago & had forgotten a lot of it, so it's helpful to review a lot of that stuff.

With the help of your input here, I've decided that it's time to get the C-Sonnar for my general use.

So, I'm putting my Leica 50 Summicron up for sale on ebay next week to finance it. It's amazing how much it's appreciated in value since I bought it.

However, as good a lens as the Summicron is, I don't really use it. I much prefer the Rollei 40/2.8 Sonnar for general use. When I need a faster lens, I'm mostly using my Biogon 35/2.

I like the fact that the C-Sonnar will give me a different look without any added bulk from the Summicron. I think that I'm more likely to reach for it in portrait-type situations or when I just want something different. The fact that I can leave it on & continue to get sharp pictures when stopped down is an added plus. I don't really need or want two 50's, so the high price that the Summicron is selling for these days means that it will simply be a trade at no cost to me. I might even make a few bucks on the deal.

You've been more help than you know. You're a good guy to spend so much time bringing me up to speed.

All the best & happy holidays! 🙂
Bill