Just got a C-Sonnar!

A curiosity - how do you buy an f1.5 lens that's "optimized" for f2.8? Why not just make f2.8 the maximum aperture?

I mean, I may be interested in the lens but I want to be able to use the f1.5 aperture since, I believe, a lens made at that aperture should be able to be shot at that aperture...I'm having a difficult time understanding the reasons for paying excess $$ to get an f2.8 lens.. regardless if the bokeh is "similar to" an f1.5 lens - it doesn't gain me any shutter speed in low light; it still has to be exposed at f2.8...

Curious,
Dave
 
dcsang said:
A curiosity - how do you buy an f1.5 lens that's "optimized" for f2.8? Why not just make f2.8 the maximum aperture?

I mean, I may be interested in the lens but I want to be able to use the f1.5 aperture since, I believe, a lens made at that aperture should be able to be shot at that aperture...I'm having a difficult time understanding the reasons for paying excess $$ to get an f2.8 lens.. regardless if the bokeh is "similar to" an f1.5 lens - it doesn't gain me any shutter speed in low light; it still has to be exposed at f2.8...

Curious,
Dave
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If they made it an f2.8 lens, it would still have focus shift, meaning it might not be usable until f4 or 5.6
 
dcsang said:
.... I may be interested in the lens but I want to be able to use the f1.5 aperture since, I believe, a lens made at that aperture should be able to be shot at that aperture...

Curious,
Dave
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Dave, I shoot mine in clubs and other low light situations at f1.5 with good results. I avoid shooting at minimum focus distance, though. That's where the focus shift impact is most evident (where the dof is thinnest).

I prefer to shoot standard portraits with the lens at f2.8 because IQ is quite close to wide open performance and margin for focus error (wider dof) is greater.
 
Chriscrawfordphoto said:
If they made it an f2.8 lens, it would still have focus shift, meaning it might not be usable until f4 or 5.6
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Maybe that's my issue.
The whole focus shift thing - I've never gotten my head around it - and, to be honest, don't pay attention to it.

Now, that's not to say that I don't believe it doesn't exist, it's just that I don't know how it manifests itself in film images (or digital for that matter) - to me, because of what I shoot, I only care if I get the image that I want (and my clients like) 🙂

So, that being said, why even bother making an f1.5 lens that has this "focus shift" and instead make a "proper" f2.8 lens and just call it that.

Cheers,
Dave
 
MCTuomey said:
Dave, I shoot mine in clubs and other low light situations at f1.5 with good results. I avoid shooting at minimum focus distance, though. That's where the focus shift impact is most evident (where the dof is thinnest).

I prefer to shoot standard portraits with the lens at f2.8 because IQ is quite close to wide open performance and margin for focus error (wider dof) is greater.
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This sort of helps me understand a bit better Mike. I still don't get the whole focus shift thing.

I know it's not just a "digital" thing but "back in the day" - i.e. when I was first learning photography, 32 years ago or more now - I had never ever heard of anyone complaining of "focus shift" from any lenses..

Cheers,
Dave
 
Dave,

The reason they made the Sonnar with focus shift is because that is an inherent property of that optical design. Now, why make Sonnars, when a Tessar or Gauss design (to mention two common 50mm lens types) has no shift? Gauss designs like the Leica Summicron and the ZM Planar (and most modern 50mm lenses for SLRs) tend to produce harsh bokeh. Not always; the Summicron's bokeh isn't bad, but my Nikon 50mm f1.4 AF-Nikkor and my Olympus 50mm f1.8 OM lens both have incredibly harsh bokeh. The Summicron is not bad, but the Sonnar has even nicer bokeh. If you like to do portraits and other pics that sometimes have out of focus backgrounds, then a Sonnar is a better lens. If you rarely or never do, if you shoot everything at f8 or below, then you won't see a difference in image quality and would be better off with a Summicron or ZM Planar because both are sharp and properly focused at all apertures and a used Summicron or new Planar is cheaper than a ZM Sonnar...and both lenses are usable at f2 if you sometimes need the speed.
 
MCTuomey said:
+1 what DubilUC posted

shooting fast normal or tele lenses wide open at/near minimum focus distance will result in at least a fair % of misfocused images. some with one eye OOF, both eyes OOF, nose/ears in focus unintentionally, and so on. it's just a function of very thin dof at full aperture and mfd. the nice thing about the c-sonnar is that it preserves nearly wide open image quality around f2.8. for me, that's focus error cushion. that's why i like to shoot f2.8-f4 with it and why f2.8 optimization does make some sense in my case.

when i use the c-sonnar wide open i like to be 5-6 feet or more from my subject. gives me room for error.
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Exactly, at 2m @ 1.5, you will have around 10" DOF, still front loaded a little, but as an example: A tight head shot focused on the eyes, will also have the nose, eyes and mouth in focus, but not the ears. And that beautiful OOF background to boot. But, 2m is a bit close for a Portrait for a 50mm on a film, -- For Me --.

It is a nice lens, with some great personality. It is a nice lens for m4/3, yes, with some purple edges on back-lit stuff (easily taken care of).
I have to shoot a roll on my M5, it has been sitting on my G1 for too long. A 3 day weekend for me starts now, so this is my "Film" break. 😛
 
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Chriscrawfordphoto said:
Dave,

The reason they made the Sonnar with focus shift is because that is an inherent property of that optical design. Now, why make Sonnars, when a Tessar or Gauss design (to mention two common 50mm lens types) has no shift? Gauss designs like the Leica Summicron and the ZM Planar (and most modern 50mm lenses for SLRs) tend to produce harsh bokeh. Not always; the Summicron's bokeh isn't bad, but my Nikon 50mm f1.4 AF-Nikkor and my Olympus 50mm f1.8 OM lens both have incredibly harsh bokeh. The Summicron is not bad, but the Sonnar has even nicer bokeh. If you like to do portraits and other pics that sometimes have out of focus backgrounds, then a Sonnar is a better lens. If you rarely or never do, if you shoot everything at f8 or below, then you won't see a difference in image quality and would be better off with a Summicron or ZM Planar because both are sharp and properly focused at all apertures and a used Summicron or new Planar is cheaper than a ZM Sonnar...and both lenses are usable at f2 if you sometimes need the speed.
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+1
Thanks for design details of how different designs render OOF areas. as a side, I like the Sonnar, over 50mm Nokton OOF more, the FS doesn't bother me, I consider it like having two lenses in one... Always sharp from f/2.8 on, and that "Special" rendering at f/1.5-f/2 for 1m-2m close ups.
 
dcsang said:
This sort of helps me understand a bit better Mike. I still don't get the whole focus shift thing.

I know it's not just a "digital" thing but "back in the day" - i.e. when I was first learning photography, 32 years ago or more now - I had never ever heard of anyone complaining of "focus shift" from any lenses..

Cheers,
Dave
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In my case, Dave, no one I knew owned the magically fast glass way back then (I'm real vintage), the kind of lenses that suffer from the shift. Probably why I never heard of it, either. We all shot f2 and slower lenses and were happy with it.

Thing is, since I picked photography back up, every lens I've owned that had focus shift I've really really liked.
 
Chriscrawfordphoto said:
Dave,

The reason they made the Sonnar with focus shift is because that is an inherent property of that optical design. Now, why make Sonnars, when a Tessar or Gauss design (to mention two common 50mm lens types) has no shift? Gauss designs like the Leica Summicron and the ZM Planar (and most modern 50mm lenses for SLRs) tend to produce harsh bokeh. Not always; the Summicron's bokeh isn't bad, but my Nikon 50mm f1.4 AF-Nikkor and my Olympus 50mm f1.8 OM lens both have incredibly harsh bokeh. The Summicron is not bad, but the Sonnar has even nicer bokeh. If you like to do portraits and other pics that sometimes have out of focus backgrounds, then a Sonnar is a better lens. If you rarely or never do, if you shoot everything at f8 or below, then you won't see a difference in image quality and would be better off with a Summicron or ZM Planar because both are sharp and properly focused at all apertures and a used Summicron or new Planar is cheaper than a ZM Sonnar...and both lenses are usable at f2 if you sometimes need the speed.
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Chris,

Thanks for the explanation - I don't want to give up my Summilux (pre-ASPH) but I'd be willing to see what this lens can do at the given apertures.

That said, this concept of "optimization" at a particular f-stop.. can you (or anyone for that matter) explain that one to me? Does this mean that if it's optimized for f1.5 that it "sucks" at f2.8 and vice versa?

Cheers,
Dave
 
If I still shot film, it would be because of this lens. It is the only m-mount lens I'm holding on to just in case... I use it every now and then with the Olympus E-P2, sometimes in combination with the Grainy B&W art filter.
 
dcsang said:
Chris,

Thanks for the explanation - I don't want to give up my Summilux (pre-ASPH) but I'd be willing to see what this lens can do at the given apertures.

That said, this concept of "optimization" at a particular f-stop.. can you (or anyone for that matter) explain that one to me? Does this mean that if it's optimized for f1.5 that it "sucks" at f2.8 and vice versa?

Cheers,
Dave
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The "optimization" simply makes the focus very accurate at f1.5, with the "shift" occurring between f2.8 and f4. Unoptimized, the accurate focus is at f2.8 and anything larger gets shifted. Here is an excellent review by Roger Hicks that talks about the shift/optimization.

http://www.rogerandfrances.com/subscription/ps%20firstlook%20sonnar%2050.html
 
dcsang said:
Chris,

Thanks for the explanation - I don't want to give up my Summilux (pre-ASPH) but I'd be willing to see what this lens can do at the given apertures.

That said, this concept of "optimization" at a particular f-stop.. can you (or anyone for that matter) explain that one to me? Does this mean that if it's optimized for f1.5 that it "sucks" at f2.8 and vice versa?

Cheers,
Dave
Click to expand...

As I understand it, "optimized" practically means the dof is distributed more or less one-third/two-thirds around the sharpest point of focus at the optimized aperture. if your c-sonnar is optimized at f2.8, it will tend to front focus when shooting at f1.5. if you c-sonnar is optimized at f1.5, it will tend to back focus when shooting at f2.8. this focus "waffling" is due to the shift of focus away from the camera position as the lens is stopped down at a given focus point, ie the focus shift.

from about f4-4.5 focus shift is not much of an issue with either optimization because it is "covered" by the wider dof available as the lens is stopped down.
 
MCTuomey said:
As I understand it, "optimized" practically means the dof is distributed more or less one-third/two-thirds around the sharpest point of focus at the optimized aperture. if your c-sonnar is optimized at f2.8, it will tend to front focus when shooting at f1.5. if you c-sonnar is optimized at f1.5, it will tend to back focus when shooting at f2.8. this focus "waffling" is due to the shift of focus away from the camera position as the lens is stopped down at a given focus point, ie the focus shift.

from about f4-4.5 focus shift is not much of an issue with either optimization because it is "covered" by the wider dof available as the lens is stopped down.
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Thanks Mike..

I guess if it's "optimized" at f1.5.. then shooting at f2.8 from a distance greater than the "minimal focus distance" may allow for accommodation of the "greater" DOF thereby getting more "things" in focus in your image (i.e. eyes and nose versus just the eyes).

Is this what you meant by shooting it at 5-6 ft away versus 3 ft? (I think it was you who said that *LOL*) 🙂

CHeers,
Dave
 
dcsang said:
Thanks Mike..

I guess if it's "optimized" at f1.5.. then shooting at f2.8 from a distance greater than the "minimal focus distance" may allow for accommodation of the "greater" DOF thereby getting more "things" in focus in your image (i.e. eyes and nose versus just the eyes).

Is this what you meant by shooting it at 5-6 ft away versus 3 ft? (I think it was you who said that *LOL*) 🙂

CHeers,
Dave
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yes dave, the greater distance will increase the dof at a given aperture and so will offset some or all of the focus shift. but an f1.5 optimized lens exhibits the worst effect of the focus shift at f2.8, so increasing subject distance is less helpful. imho, if you have an f1.5 optimized lens you should shoot it at f1.5 close up and avoid f2.8ish apertures if you're at min focus distance. f4 and down are good at all distances.

an f2.8 optimized lens exhibits the worst of the shift effect at f1.5. imho if you have an f2.8 optimized lens you should shoot it at f2.8 close up and not so much at f1.5 at min focus distance (unless you use the "lean" or other workaround). again, f4 and down, you're good to go at any distance.
 
MCTuomey said:
sug, mine are in my gallery "simple shots" ... sorry for my part in the long digression.
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Mike, thanks for that. I love that silly dog photo. Oh that is just priceless. There are so many great shots in your gallery with this lens.

Wide open aperture and the whole optimization discussion are all important aspects to know this lens I'm sure, but the character, handling and the actual photos are things I want to know and see more. 🙂
 
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