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Archive 2010 · Zeiss 25mm ZF.2 announced
  
 
edwardkaraa
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p.3 #1 · Zeiss 25mm ZF.2 announced


Well, your findings seem to agree with the MTF of these 2 lenses that are provided by Zeiss. I tend to believe these MTF more than any independent reviewers whose techniques are most of the time lacking.

HerbChong wrote:
sharper across the field and esp in the corners.

Herb...





Jun 09, 2010 at 09:14 PM
wayne seltzer
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p.3 #2 · Zeiss 25mm ZF.2 announced


HerbChong wrote:
based on my examination of other Zeiss 21/2.8 images at 100%, mine is not different in any significant way from others. if anything, it shows even people who own Zeiss lenses are sometimes sloppy at simply things like focus and post processing. dead center at f8 or f11, my 25 is sharper than my 21 though only just barely visible under ideal circumstances. it does slightly better in the corners than the 21.

Herb...



Herb,

I would expect these lenses to have very close center sharpness at f8 but how about at f4 of f5.6? Is there any difference?
Concerning the corner sharpness being better in the 25, what type of shot and how are you comparing them since the 25 has alot more field curvature? Are you doing the comparison shots agains a flat building wall or are you doing a normal landscape shot where the lower corners end up in the close foreground and thus can be rendered sharper by a lens with more field curvature?

Z* 25/2.8 owners,

Is there anything this lens can do that, that both the 21 and 28 could not do better?
This lens seems like a value (aka poorman's) 21 with a floating element like the 28 to do close focusing better and is just not as well corrected for CA like the 21.
Sorry, just trying to figure out the use for this lens, since it is easily the least posted Zeiss lens in the forum.
Let's see a shot with the 25 that shows its unique strength.




Jun 09, 2010 at 09:15 PM
Andi Dietrich
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p.3 #3 · Zeiss 25mm ZF.2 announced


the most disappointing news is that Zeiss needed another 6 or 8 months to deliver something which they could have done long before and announced as a redesign. IMO they dont take their business very seriously.

Lotusm50 wrote:
which are done at infinity,


what is their definition of infinity? 50x the focal lenth = 1.25 meters? I just wonder



Jun 09, 2010 at 09:21 PM
denoir
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p.3 #4 · Zeiss 25mm ZF.2 announced


Lotusm50 wrote:
Looking at Zeiss MTF's, which are done at infinity, at f5.6 the ZF 21mm and the ZF 25mm are very comparable. The 25mm could indeed perform better the the edges of the frame at f5.6 (might depend on the nature of the subject, to some extent), while we might expect the 21mm to be a little better in the center.


Um, what charts are you looking at? The Zeiss ZF MTF charts that I'm looking at here show that the 25 is weaker in the corners at f/5.6. The 25 start dipping at 17 mm (tangential) and stops lower than the 21 that does a sharper but shallower dip around 20mm. I won't even go into the sagittal lines which are significantly worse.



Jun 10, 2010 at 12:41 AM
Lotusm50
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p.3 #5 · Zeiss 25mm ZF.2 announced


denoir wrote:
Um, what charts are you looking at? The Zeiss ZF MTF charts that I'm looking at here show that the 25 is weaker in the corners at f/5.6. The 25 start dipping at 17 mm (tangential) and stops lower than the 21 that does a sharper but shallower dip around 20mm. I won't even go into the sagittal lines which are significantly worse.



But as strong, if not bit stronger, to the edges of the frame. I said edges, not corners (I already said its a little weaker in the corners). It's weaker in the last couple of millimeters of the frame (absolute corner). And as I said, the 21 is a bit stronger in the center. Also the relative differences between the sagittal and tangental curves lead to the point made that, "{might depend on the nature of the subject)".




Jun 10, 2010 at 12:53 AM
denoir
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p.3 #6 · Zeiss 25mm ZF.2 announced


Those are mighty big absolute corners in that case - from about 15 mm to 25mm. The 25/2.8 may possibly have an advantage in sharpness around 10mm, but it's difficult to read from the chart. To be honest we're splitting hairs up until 15 mm and there is also something to be said for a smoother edge/corner transition at the cost of some sharpness.

Having said that, there is a perfectly simple explanation that fits what Herb, Lloyd and the MTF measurements that Mike provided say. It may very well take up to f/11 to get the absolute corners sharp and beyond that point the 25 may be less diffraction limited than the 21. Lloyd was only commenting the corners at f/11 and that doesn't exclude that the overall sharpness is better compared to the 21 at smaller aperture. In fact that's exactly what the third party MTF measurements say - at f/16 the 25 definitely takes the lead if the numbers are to be believed.

Lloyds comments about it being almost as sharp as the 16-35 was wide open or near wide open and the MTF charts for that look quite differently. One of the defining properties of the 21/2.8 is that it's very sharp wide open across the whole frame except the extreme corners. It's MTF curve at f/2.8 is similar to f/5.6 while the 25 at f/2.8 behaves quite differently.

So I don't really think there is any contradiction here.



Jun 10, 2010 at 01:52 AM
Mirek Elsner
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p.3 #7 · Zeiss 25mm ZF.2 announced


Z* 25/2.8 owners, Is there anything this lens can do that, that both the 21 and 28 could not do better?

Not an owner, they did not make it in the EF mount, which I use. I believe the 25 focuses closer than 21 or 28.



Jun 10, 2010 at 02:01 AM
Lotusm50
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p.3 #8 · Zeiss 25mm ZF.2 announced


The co

denoir wrote:
Those are mighty big absolute corners in that case - from about 15 mm to 25mm. The 25/2.8 may possibly have an advantage in sharpness around 10mm, but it's difficult to read from the chart. To be honest we're splitting hairs up until 15 mm and there is also something to be said for a smoother edge/corner transition at the cost of some sharpness.

Having said that, there is a perfectly simple explanation that fits what Herb, Lloyd and the MTF measurements that Mike provided say. It may very well take up to f/11 to get the absolute corners sharp and
...Show more


The corner is NOT at 25mm! Do the math. The absolute end of the corner is at 21.6mm. Zeiss put the graph to 25mm for completeness (or convention, or some other anal reason). My reading of their MTF's. is that it is really only in the last 2mm,19-21mm, where you can potentially see a difference between the 21 and 25mm at f5.6 (in addition, of course, to the modest advantage in the very center). You probably won't see much of a difference in the absolute corner at all at f8. Through nearly all of what some have called "zone B", the 25mm at f5.6 is at least as good as the 21mm at f5.6 -- and with the right subject, "might" show to be better -- and that is very well what Herb might be seeing. Neither Herb nor I said the difference was big. It is indeed small, if there. Finally, I should point out that the 25mm at f5.6 is better than the 21mm at f2.8 -- particularly through Zone B. The are only about the same in the very center and the absolute corner.

Rather than talk about and interpret what others may or may not have said, first hand use of the lens may prove useful for you. Use it for its intended use, landscape, and for "unusual" or "interesting" image quality close up. Then form an opinion of the lens.




Jun 10, 2010 at 03:34 AM
denoir
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p.3 #9 · Zeiss 25mm ZF.2 announced


It's difficult to compare two MTF charts in two separate PDFs when the scaling is different. I've put them together for reference (the grid has been aligned so they should match). The red is the 21.







So the reading of this is that the 21 starts off sharper but the 25 takes over up until about 17-18mm (sagittal) with a variation as to when the 25 takes over depending on resolution. As for tangential, they are identical at low resolution but the 25 significantly deteriorates at the two higher resolutions.

The conclusion that I draw here is that the main difference is in the tangential direction for medium and high frequency patterns. In short they are pretty much matched (the 21 being slightly better in the center and corners and the 25 being slightly better in mid frame) as far as the sagittal component is concerned as well as the low resolution tangential component. There is however a significant difference in the higher tangential radial components - meaning that the 21 can resolve finer detail.

As for comparing the 21 @ f/2.8 to the 25 @ f/5.6 - that's just silly.

Rather than talk about and interpret what others may or may not have said, first hand use of the lens may prove useful for you. Use it for its intended use, landscape, and for "unusual" or "interesting" image quality close up. Then form an opinion of the lens.

I prefer tests to anecdotal evidence - even if that evidence is my own. Having said that I really couldn't care less about the 25. Not interested in it the slightest. That was pretty much my point from the start but you and some others took offense at Lloyd's review which I referred to. Hence this discussion.

This specific topic of the sharpness follows Herb's claim that the 25 is sharper across the frame than the 21, which is to say the least a pretty controversial statement. I have been trying to find support for it and apart from the diffraction theory that I put forward I have not found anything - including the MTF charts - that would support it.


Edited on Jun 10, 2010 at 09:35 AM · View previous versions



Jun 10, 2010 at 04:28 AM
philip_pj
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p.3 #10 · Zeiss 25mm ZF.2 announced


Being a Sony user I have no horse in this 'race', both appear to be fine lenses indeed - so it speaks volumes that the 25mm does so well against lavishly acclaimed wider brother.

The distortion figures are expectedly worse for the moustachioed 21mm at closer to on-axis, and correction favours the 21mm also, but not optical vignetting, also to be expected. Illuminance at f5.6 is much superior for the 25mm especially into the corners, almost a shallow linear affect.

Denoir, the broken lines are tangential (lateral definition across the frame) and the unbroken lines are sagittal ('arrow' away from frame centre, or longitudinal definition with distance moving away from the camera). There is nothing really in it for the sagittal MTF except for the curvature noted in the 25mm at the long frame edge point - the significant kick upwards which coincides with peak distortion.

The 21mm has a better tangential performance especially for the crucial high frequency 'fine detail' 40 lpmm line, much more parallel to the paired sagittal line, but the 25mm's line levels off at a reasonable level (45%) and will deliver very good cross-field definition at lower contrast. For an overall assessment I think it useful to average the two line pairs, for a resolution comparison. Corner performance should be virtually identical at mid apertures.

Zeiss also have the convention of reprting MTF at wide open and two stops down. By f8 things may be a little different and the f11 referred to above will benefit the 25mm more than the 21mm with DOF, all other things being equal. It is clear from the charts provided above that neither lens needs that near-diffraction aperture - most makers would be delighted to get real world 40 lpmm MTF of 50% in the corners by f5.6, so I am inclined to agree that Lloyd might be zeroing in on close focus with the 25mm and seeing curvature. Otherwise he got a poor sample or he is wrong, simple as that. If you want to see some dramatic curvature and poor corners, take a look at the ZF28 f2 data sheet..then again, Lloyd most likely panned that one also.

These two here are *much* more alike than dissimilar, and if one does not need the extreme AOV of the 21mm, the 25mm looks like a great bargain for its intended usage at half the price, with a better filter size and a weight advantage also. I'm another who would like to see more non-close focus images from it.

All in all, only minor issues for the 25mm which could be expected to be a great buy, IMHO. As for comparisons with a Canon zoom, please..



Jun 10, 2010 at 06:57 AM
 

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edwardkaraa
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p.3 #11 · Zeiss 25mm ZF.2 announced


Agreed with Philip. In fact, the MTF of the 25 look surprisingly good compared to the 21mm superstar. They are very close imho, and a quick glance at the MTF of the 28 and 35 will show this 25 is actually a very good lens. The problem of the 25 is that it carries on the mostly undeserved bad reputation of its Contax predecessor.


Jun 10, 2010 at 08:30 AM
denoir
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p.3 #12 · Zeiss 25mm ZF.2 announced


philip_pj wrote:
Denoir, the broken lines are tangential (lateral definition across the frame) and the unbroken lines are sagittal ('arrow' away from frame centre, or longitudinal definition with distance moving away from the camera).


Yes, sorry, I reversed them in the text. Thanks - I've corrected it now. A bit of early morning dyslexia I'm afraid

For an overall assessment I think it useful to average the two line pairs, for a resolution comparison.

No, no, that would not be advisable. These are the two dimensions of the smear - you should absolutely not average the radial and tangential lines. Possibly if you want a one-value comparison you can take the ARGMAX(R,T) but that's misleading as well. Remember that this is a description of the point spread function - both dimensions are crucial. It doesn't help if you are excellent in only one direction and suck in the other.

Apart from that your assessment is correct. They are similar except for high frequency patterns (fine detail at 40 lp/mm) where the 25 doesn't do so well in the tangential component.



Jun 10, 2010 at 09:44 AM
HerbChong
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p.3 #13 · Zeiss 25mm ZF.2 announced


i don't know about wider than f8 since i never shoot either of the lenses below f8 and even f8 is only under exceptional circumstances. i do normal landscape shots with as much DOF as i can manage which is why i am unconcerned with field curvature or the small amount of distortion that should be there. the sharpness differences are slight but real. field curvature can account for some of the corner sharpness differences i observe but i also see that infinity in the corners seems very comparable. the differences are not large and unless you compare side by side captures of the same scene, essentially impossible to discern.

Herb...

wayne seltzer wrote:
I would expect these lenses to have very close center sharpness at f8 but how about at f4 of f5.6? Is there any difference?
Concerning the corner sharpness being better in the 25, what type of shot and how are you comparing them since the 25 has alot more field curvature? Are you doing the comparison shots agains a flat building wall or are you doing a normal landscape shot where the lower corners end up in the close foreground and thus can be rendered sharper by a lens with more field curvature?




Jun 10, 2010 at 03:34 PM
RickPerry
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p.3 #14 · Zeiss 25mm ZF.2 announced


philber wrote:
I would just like to point out that there never was a ZE 25. By the time it could have been released, the ZF 25 was pulled, due to "ongoing redesign". So if one fits all pieces of the puzzle together, this ZF.2 25mm is simply the chipped version of the ZF 25, an almost nil investment for Zeiss, as opposed to the development of a ZE version.
Thus, it stands to reason that the redsigned 25 is still ahead of us...
Sorry Lotus (brilliant post BTW!), but no cigar!



I asked Martin Klottig (Head of Marketing for Zeiss America) if he knew about a release date for the ZE 25mm - his anaswer was:

Dear Rick,

thank you for your mail. It is right we announced the Distagon T* 2,8/25 ZF.2 for Nikon. Unfortunately I cannot tell you yet when the 25mm will become available for ZE. But I think you will not have to wait for too long.


Best regards from sunny Germany


--- Martin


Carl Zeiss AG
Camera Lens Division



Jun 11, 2010 at 11:56 AM
rsolti13
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p.3 #15 · Zeiss 25mm ZF.2 announced


So is the consensus that the ZE will be a redesign of the 25? If so, I would assume they would also put out a ZF version at the same time......

Great.....more money to spend



Jun 11, 2010 at 03:14 PM
Sam tran
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p.3 #16 · Zeiss 25mm ZF.2 announced


...Unfortunately I cannot tell you yet when the 25mm will become available for ZE. But I think you will not have to wait for too long...

I bet we won't have to wait too long for the ZE 25mm version. I borrowed the 35/f2 last week and compared with 16-35 MK II, the ZE 35/2 has CA all over f-stops, and reading many user reviews confirmed it, I hope the ZE 25mm will get rid off it. Otherwise, beside the 3D look and color rendered, I rather stay with my 16-35 MK II and wait for a better 25mm ZE.



Jun 14, 2010 at 09:17 PM
denoir
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p.3 #17 · Zeiss 25mm ZF.2 announced


Sam tran wrote:
I bet we won't have to wait too long for the ZE 25mm version. I borrowed the 35/f2 last week and compared with 16-35 MK II, the ZE 35/2 has CA all over f-stops, and reading many user reviews confirmed it, I hope the ZE 25mm will get rid off it. Otherwise, beside the 3D look and color rendered, I rather stay with my 16-35 MK II and wait for a better 25mm ZE.


Interesting. I've found a bit of LoCA in OOF areas and slight standard CA in the corners but that's it. It's in a completely different league than my 16-35/II. I mean really, there is no comparison - the 16-35 truly sucks at 35mm until about f/8. The only reason I'm keeping it is because it is weather sealed and more convenient when I'm really pressed for time.



Jun 14, 2010 at 09:49 PM
Sam tran
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p.3 #18 · Zeiss 25mm ZF.2 announced


I'm keeping it is because it is weather sealed and more convenient when I'm really pressed for time.
Same here, and since I can afford to wait - rather spend $1k for the 35/2 - and see how the 25/2 ZE would look in term of CA. I crossed my fingers for this.



Jun 14, 2010 at 11:10 PM
philber
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p.3 #19 · Zeiss 25mm ZF.2 announced


I am with Denoir here. My 35 ZE had just a trace of CA, and the 16-35 I tried had lots. No comparison. Also, my information says that this ZF 25 will never have a ZE sibling. When one does come out, it will be the redesigned version.


Jun 15, 2010 at 04:55 AM
Lotusm50
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p.3 #20 · Zeiss 25mm ZF.2 announced


Perhaps the question to Zeiss should have been more pointed. Something along the lines of, "When the ZF.2 lenses were announced, the press release said, 'We are currently completely reworking and optimizing the Distagon T* 2.8/25 ZF. As a result, it will be available for other mounts somewhat later.' Now that the ZF.2 25mm have appeared without an any optical change, will we still see a "completely reworked" 25mm?, and if so, when?"

I don't pretend to know the answer to that question, but it seems to me that the introduction of the ZF.2 25mm suggests that we won't see a reworked 25mm appearing anytime soon. Zeiss should be asked for a clarification so we can better understand their plans and intentions in the context of their announcements.


RickPerry wrote:
I asked Martin Klottig (Head of Marketing for Zeiss America) if he knew about a release date for the ZE 25mm - his anaswer was:

Dear Rick,

thank you for your mail. It is right we announced the Distagon T* 2,8/25 ZF.2 for Nikon. Unfortunately I cannot tell you yet when the 25mm will become available for ZE. But I think you will not have to wait for too long.

Best regards from sunny Germany

--- Martin

Carl Zeiss AG
Camera Lens Division




Jun 15, 2010 at 01:56 PM
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