Ultron 28/2 Review

[padraigm]

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Sean gave another great review of the new VC lens and seeing the resolution pictures one has to be quite surprised. I don't know as stated, what the design constraints are for VC to be releasing lenses like this that clearly have stark issues. But the price well I guess we can put up with a lot. I have the 35 1.4 also for my compact low light work and I knew what it's limitations were before I bought it. The speed , size and price in the end became just to hard to pass up. But it is still surprising thought. Can someone knowledgeable comment on why there seems to be such focus shifts with the new VC lenses? I know with most lenses there is always a compromise somewhere. I would just like to understand this one better.

[sean_reid]

Sean gave another great review of the new VC lens and seeing the resolution pictures one has to be quite surprised. I don't know as stated, what the design constraints are for VC to be releasing lenses like this that clearly have stark issues. But the price well I guess we can put up with a lot. I have the 35 1.4 also for my compact low light work and I knew what it's limitations were before I bought it. The speed , size and price in the end became just to hard to pass up. But it is still surprising thought. Can someone knowledgeable comment on why there seems to be such focus shifts with the new VC lenses? I know with most lenses there is always a compromise somewhere. I would just like to understand this one better.

 

Thanks for the article comments. Lens design is certainly not simple and I won't pretend to be a lens designer here. But note the following trend among fast CV (rather than VC) lenses: It's usually most vociferous from people who've never actually read the review in question. <G>

 

Focus shift:

 

CV 35/1.4

CV 40/1.4

CV 28/2.0

 

 

Little or no focus shift:

 

CV 28/1.9 Aspherical

CV 35/1.2 Aspherical

CV 35/1.7 Aspherical

CV 50/1.5 Aspherical

 

Interesting trend - yes? Now consider the nature of spherical aberrations. Here's an interesting page that I linked in the review: Spherical aberration

 

Keep in mind that at apertures like F/2.8 and F/4.0, the 28/2 is going to show strong resolution *somewhere*. It just won't be at the plane where the lens was focused wide open. That fact sometimes seems to keep some people from recognizing focus shift in certain lenses. They may point to examples made at, say, F/4.0 that show excellent resolution. But of course, the plane where that focus exists isn't the same one they'd see if the lens was wide open.

 

The last time I noted the focus shift in a new CV lens, the 35/1.4, there was a firestorm of protest and accusation on a certain other forum. I imagine we may see that all over again.

 

Cheers,

 

Sean

[thompsonkirk]

Whew, I'm glad I waited for this review. I traded in my CV 28mm 1.9 on a Summicron, but have since felt cautious about carrying a >$3K lens in some of the places I like to shoot. I thought of buying the CV f2 to use on my older & somewhat battered M8 body when around grit, sand, unpleasant weather, or unpleasant people. But I don't enjoy focus shift at the apertures I'm most likely to use, so I'll just let that option pass, thank you.

 

Again Sean's review proves to be my most valuable Leica 'accessory' in relation to cost!

 

Kirk

[gravastar]

Sean, many thanks for the review - most informative.

 

What I would like to see Cosina make available for their older lenses are replacement bayonets in the new format, even though there may be screws in the coding area. That's assuming there wouldn't be any focus/tolerance issues in doing this.

 

Bob.

[sean_reid]

Whew, I'm glad I waited for this review. I traded in my CV 28mm 1.9 on a Summicron, but have since felt cautious about carrying a >$3K lens in some of the places I like to shoot. I thought of buying the CV f2 to use on my older & somewhat battered M8 body when around grit, sand, unpleasant weather, or unpleasant people. But I don't enjoy focus shift at the apertures I'm most likely to use, so I'll just let that option pass, thank you.

 

Again Sean's review proves to be my most valuable Leica 'accessory' in relation to cost!

 

Kirk

 

Thanks Kirk. If you don't need the speed - in those iffy places - consider finding a good copy of the CV 28/3.5. That would really be worth having because its also very compact.

 

Cheers,

 

Sean

[sean_reid]

Sean, many thanks for the review - most informative.

 

What I would like to see Cosina make available for their older lenses are replacement bayonets in the new format, even though there may be screws in the coding area. That's assuming there wouldn't be any focus/tolerance issues in doing this.

 

Bob.

 

Hi Bob,

 

The screw location is the the trick. The new bayonet uses, of course, new screw locations. Still....it could be done. I end up sending my non-coded lens to John Milich to be milled.

 

Cheers,

 

Sean

[lxlim]

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Thanks, Sean, once again for the meticulous attention to details.

 

Coincidentally, my sister-in-law is getting married next week and I was thinking of getting a faster lens than my CV 28f3.5. Its a timely review, I was going through you 28mm reviews barely 8 hours ago

[lct]

Hi Sean, i see very little focus shift with my CV 35/1.4 SC at f/1.4 as if the lens were calculated to be used at full aperture. How is the 28/2 at f/2 from this standpoint?

[jlancasterd]

If you don't need the speed - in those iffy places - consider finding a good copy of the CV 28/3.5. That would really be worth having because its also very compact.

Sean

 

Another vote here for the CV 28/3.5 - it's the 'permanent' lens on my M8 and regularly produces pin-sharp images, capable of enlargement to poster size - up to 90cm wide. The CV 28/1.9 will also produce cracking images provided that you don't want to shoot into the sun.

[ArtZ]

...I see very little focus shift with my CV 35/1.4 SC at f/1.4 as if the lens were calculated to be used at full aperture

 

I bought at Camera Quest this summer a CV 35/1.4 (MC) just for its size, weight, softness @ f1.4... and price. John Milich coded it for me. I had heard about the focus shift on this lens but, to be honest, I didn´t care about it (considering its price).

 

I've done more elaborate tests than dirty tests but I couldn't call them professional tests either.

 

My conclusion concerning my copy is it has very (and I mean VERY) little focus shift. None at f1.4 in distances up to 2.5-3 m), between 3 and 10 m I could say there's very little focus shift (front focus), nothing really important (and I'm not even 100% sure if it's focus shift or just softness) and from 10m it's difficult to say because the softness of the lens.

 

What I found about this lens is the color is a bit "cold" different of all my other 35mm lenses (Lux ASPH, MATE, Biogon or my "lost in the mail" Nokton 1.2 -sniff) BUT, since firmware 2.0, the colors with this lens have somehow improved. I will make more tests after my M8 will come back from Solms.

[sean_reid]

Hi Sean, i see very little focus shift with my CV 35/1.4 SC at f/1.4 as if the lens were calculated to be used at full aperture. How is the 28/2 at f/2 from this standpoint?

 

Hi LCT,

 

By definition, a lens can not show focus shift at maximum aperture. Focus shift is when a lens' peak focus changes (to different distances) as it is stopped down.

 

I also found the 35/1.4 to have good resolution, on center, wide open. The same is true for the CV 28/2.0. Both also hold their resolution fairly well when stopped down one stop.

 

Best,

 

Sean

[sean_reid]

I bought at Camera Quest this summer a CV 35/1.4 (MC) just for its size, weight, softness @ f1.4... and price. John Milich coded it for me. I had heard about the focus shift on this lens but, to be honest, I didn´t care about it (considering its price).

 

I've done more elaborate tests than dirty tests but I couldn't call them professional tests either.

 

My conclusion concerning my copy is it has very (and I mean VERY) little focus shift. None at f1.4 in distances up to 2.5-3 m), .

 

Hi,

 

Again, a lens can't show focus shift wide open. The focus wide open is the base line reference. Assuming that the RF in a given body is working correctly (adjusted properly) a lens that front-focuses or back-focuses wide open needs to be adjusted by a lens technician.

 

Cheers,

 

Sean

[lct]

...By definition, a lens can not show focus shift at maximum aperture...

Ah yes i did not know that thanks. Aside from flare, which is worst than my late pre-asph Summilux 35, the CV 35/1.4 SC is really good at f/1.4 indeed.

[sean_reid]

Ah yes i did not know that thanks. Aside from flare, which is worst than my late pre-asph Summilux 35, the CV 35/1.4 SC is really good at f/1.4 indeed.

 

Hi LCT,

 

The flare, of course, is to be expected in a single coated lens. Flare reduction is a primary goal of multi-coating. The reason CV offers the SC lenses is that some of us like the look of lenses that tend a bit towards veiling flare. I, personally, like those kinds of lenses much more when they're not paired with filters. The combination of filters are flare-prone lenses can be problematic.

 

This might be interesting to read: Spherical aberration

 

Is it any wonder that Leica has come to use aspherical elements in most of its fastest lenses?

 

Cheers,

 

Sean

[lct]

...The reason CV offers the SC lenses is that some of us like the look of lenses that tend a bit towards veiling flare...

I bought the SC to avoid the harsh bokeh of the NC. The SC bokeh is almost as smooth as that of my late pre-asph Summilux 35/1.4. With good sharpness and smooth bokeh, the 35/1.4 SC is a rather unique lens if one use it mainly at full aperture IMHO.

[ArtZ]

Hi,

 

Again, a lens can't show focus shift wide open. The focus wide open is the base line reference. Assuming that the RF in a given body is working correctly (adjusted properly) a lens that front-focuses or back-focuses wide open needs to be adjusted by a lens technician.

 

Cheers,

 

Sean

 

Same for me... I didn´t know that, thanks. In fact, I've been using this lens since last August always at 1.4. I will test it on other aperture values when my M8 will be back home.

[sean_reid]

I bought the SC to avoid the harsh bokeh of the NC. The SC bokeh is almost as smooth as that of my late pre-asph Summilux 35/1.4. With good sharpness and smooth bokeh, the 35/1.4 SC is a rather unique lens if one use it mainly at full aperture IMHO.

 

Hi LCT,

 

The veiling flare tends to soften the bokeh in various kinds of light.

 

Cheers,

 

Sean

[sean_reid]

Same for me... I didn´t know that, thanks. In fact, I've been using this lens since last August always at 1.4. I will test it on other aperture values when my M8 will be back home.

 

If you've been happy with it so far, maybe there's no need to test.

 

Cheers,

 

Sean

[tbarker13]

Hi,

 

Again, a lens can't show focus shift wide open. The focus wide open is the base line reference. Assuming that the RF in a given body is working correctly (adjusted properly) a lens that front-focuses or back-focuses wide open needs to be adjusted by a lens technician.

 

Cheers,

 

Sean

 

Interesting. But how does the Zeiss 50/1.5 sonnar fit into that? I'm not sure if Zeiss is still sending them out this way, but the originals were optimized at, I believe, f/2.8.

I know my first copy of that lens was off by several inches when used wide open.

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Hallo,

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[sean_reid]

Interesting. But how does the Zeiss 50/1.5 sonnar fit into that? I'm not sure if Zeiss is still sending them out this way, but the originals were optimized at, I believe, f/2.8.

I know my first copy of that lens was off by several inches when used wide open.

 

Hi Tim,

 

I need to check with Zeiss but I seem to recall something like that as well. If that is the case, it's an exception to the norm. One can always ask a tech to adjust a lens so that it gives peak focus at some aperture other than wide open but it is the norm for a (properly adjusted) lens (on a properly adjusted camera) to focus correctly when it is wide open. If the lens does not show focus shift (and many do not) then it remains correctly focused as it is stopped down.

 

One example is CV's own 35/1.2. It focused correctly, on my test camera, at F/1.2 and it remained focused correctly as it was stopped down. It would be difficult to use an F/1.2 lens that did not focus exactly as intended at F/1.2.

 

I actually heard a couple anecdotal comments about focus shift with the CV 28/2.0 on this forum (some time ago) and thought to myself: "Gosh, I hope not."

 

Cheers,

 

Sean