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Archive 2012 · 5D III for alt and MF lenses: a game changer!

  
 
wayne seltzer
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p.13 #1 · 5D III for alt and MF lenses: a game changer!


The under-corrected SA design of the ZE 35/1.4 makes it tougher to manually focus than other zeiss lenses since the different wavelengths of light don't intersect the same focus plane at the sensor. This is why the 35/1.4 has a slow focus transition from in-focus to out-of-focus. This is all mentioned in Nasse's paper on Bokeh, an excellent read. If you take a picture of the endpoints of a bunch of crayons, you will see some will be in focus and others which will be back focused or front focused even though they are the same distance away from the camera. Lloyd Chambers has shown that focusing the ZE 35/1.4 on a neutral gray tree stump is hard and doesn't appear to be really sharp because of the SA.


Apr 26, 2012 at 01:41 AM
carstenw
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p.13 #2 · 5D III for alt and MF lenses: a game changer!


wayne seltzer wrote:
The under-corrected SA design of the ZE 35/1.4 makes it tougher to manually focus than other zeiss lenses since the different wavelengths of light don't intersect the same focus plane at the sensor.


Hmm, I think that is LoCa you are describing. Spherical aberration happens when the rays near the edge of the lens don't focus at the same place the central rays do.



Apr 26, 2012 at 02:12 AM
wayne seltzer
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p.13 #3 · 5D III for alt and MF lenses: a game changer!


carstenw wrote:
Hmm, I think that is LoCa you are describing. Spherical aberration happens when the rays near the edge of the lens don't focus at the same place the central rays do.


No, what I mention is SA and LoCA and yes I know CA involves the rays which are hitting the edge of the lens and this is why the undercorrected SA behavior of the ZE 35/1.4, soft bokeh, is mainly at wide apertures because the marginal rays at the edge get blocked by the iris when stopping down. Pgs. 5, and 35-37 of Nasse's DOF and Bokeh describes this. SA is what causes focus shift in fast lenses and makes nice smooth bokeh ie. Softar but makes the lens harder to focus.
Object color does matter as well as these marginal rays get get focused at different points based on their color.
The example of the bundle of crayons I gave earlier proves that and has been demonstrated with the 35/1.4.
The ZE 35/1.4 has very little if no lateral CA but has LoCA.
According to Toothwalker, "Longitudinal chromatic aberration often operates in tandem with spherical aberration to shape the bokeh of a large-aperture lens. The combined effect of longitudinal chromatic aberration and spherical aberration is also known as spherochromatism [7,8]."



Apr 26, 2012 at 10:18 AM
Z250SA
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p.13 #4 · 5D III for alt and MF lenses: a game changer!


Chroma has to do with colour i.e. when different colours have different distance to focus. It is governed by the refractive properties of the glass.

Sphero has to do with spherical that is a much more manufacturable shape than the shape it usually approximates: parabola. When the approximation is insufficient we get detectable/visible SA.

As sphero is a result of the shape of the lens, it will blurr any wave length. Chroma will have blurrless focus, but at different positions depending on the wave length of the light in question.

A lens can have either, both or none. So there are many possibilities to prolonged discussions.



Apr 26, 2012 at 10:49 AM
AhamB
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p.13 #5 · 5D III for alt and MF lenses: a game changer!


^Obviously there is interaction between the two: the ray paths are determined by the lens shape and refractive index, and the latter is dependent on the wavelength of light (due to dispersion). Hence there is spherochromatism.
On a related note, SA can hide lateral CA.



Apr 26, 2012 at 11:08 AM
carstenw
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p.13 #6 · 5D III for alt and MF lenses: a game changer!


wayne seltzer wrote:
No, what I mention is SA


I agree with everything else that you wrote, but SA is a colour-independent phenomenon and Chromatic Aberration has to do with colour aberrations. When different wavelengths do not focus at the same point, you get colour aberrations... Unless I am reading your original text wrong somehow?

Of course, as you mention, they may happen together.



Apr 26, 2012 at 02:39 PM
Toothwalker
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p.13 #7 · 5D III for alt and MF lenses: a game changer!


With spherical aberration alone the focus is ill-defined, unless you use a reduced aperture. With longitudinal chromatic aberration alone the focus is ill-defined, unless the subject has a small wavelength spread. Now imagine that these aberrations coexist and that the amount of spherical aberration depends on the wavelength. The result is a glorious mess of fuzziness.


Apr 27, 2012 at 11:24 AM
KaaX
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p.13 #8 · 5D III for alt and MF lenses: a game changer!


LoCA is usually seen as color fringing of OOF areas... Is there any actual lens with LoCA so bad that it would be unable to have bright-red and deep-blue details in focus at the same time? detectably, not just theoretically?


Apr 27, 2012 at 11:41 AM
Toothwalker
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p.13 #9 · 5D III for alt and MF lenses: a game changer!


KaaX wrote:
Is there any actual lens with LoCA so bad that it would be unable to have bright-red and deep-blue details in focus at the same time? detectably, not just theoretically?


The phenomenon of purple fringing is very detectable.



Apr 27, 2012 at 12:08 PM
KaaX
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p.13 #10 · 5D III for alt and MF lenses: a game changer!


Toothwalker wrote:
The phenomenon of purple fringing is very detectable.


But that's not longitudinal CA, that's transverse CA, isn't it?



Apr 27, 2012 at 12:18 PM
AhamB
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p.13 #11 · 5D III for alt and MF lenses: a game changer!


KaaX wrote:
But that's not longitudinal CA, that's transverse CA, isn't it?


No; transverse/lateral CA always has the complementary color on the opposite side, so if it would be purple (blue+red/magenta) on one side, there should be yellow+green/cyan on the other side. PF is LoCA where green is in focus and blue+red are OOF, I guess.



Apr 27, 2012 at 12:39 PM
KaaX
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p.13 #12 · 5D III for alt and MF lenses: a game changer!


AhamB wrote:
No; transverse/lateral CA always has the complementary color on the opposite side, so if it would be purple (blue+red/magenta) on one side, there should be yellow+green/cyan on the other side. PF is LoCA where green is in focus and blue+red are OOF, I guess.


Um. My understanding is that purple fringing is "regular" (aka lateral) CA and yes, if it's strong you can see the yellow-green fringing on the other side.

LoCA is a problem with fast lenses shot wide open and shows up as a color cast of OOF areas -- magenta for front OOF and green-yellow for rear OOF.

Here: https://www.fredmiranda.com/forum/topic/1104043/1#10538148 take a look at the blur disks. The ones behind the plane of focus are green-tinged and the ones in front are magenta-tinged. That is LoCA.





Apr 27, 2012 at 01:50 PM
AhamB
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p.13 #13 · 5D III for alt and MF lenses: a game changer!


Strictly speaking it's not LoCA. The term wasn't invented to describe aberrations in OOF areas but those in the focal plane.

PF can be all around edges. Example that shows the difference with lateral CA: http://www.pentaxforums.com/forums/pentax-dslr-discussion/14087-impressions-tamron-70-300-a.html#post112378

On top of this, PF/LoCA goes away with stopping down, per definition, and lateral CA never goes away and can even become more evident when stopping down.



Apr 27, 2012 at 03:22 PM
KaaX
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p.13 #14 · 5D III for alt and MF lenses: a game changer!


AhamB wrote:
Strictly speaking it's not LoCA. The term wasn't invented to describe aberrations in OOF areas but those in the focal plane.


Well, that's what everyone calls it :-D But anyway, any real (as opposed to theoretical) optical system will cause rays/photons with different wavelengths to go down slightly different optical paths. If they don't converge on the plane of focus, we say that the lens exhibits LoCA. It is precisely that characteristic of the lens that causes rear OOF highlights be tinged green and front OOF highlights be tinged purple.

I got curious and dug up the toothwalker's pages: http://toothwalker.org/optics/chromatic.html So yes, it seems that purple fringing is a messy beastie in which LoCA does play its part. I still don't know the answer to my original question -- let me rephrase it in a more clear fashion:

Let's say you print a monochrome blue dot and a monochrome red dot on a sheet of paper. Arrange this sheet of paper perpendicular to the camera and focus on one of the dots. Due to LoCA they can't be both in focus (that is, in the theoretical zero-width focus plane) at the same time. Are there are real lens with LoCA strong enough make the difference between the red focus and the blue focus not fit into the DoF?




Apr 27, 2012 at 03:55 PM
Toothwalker
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p.13 #15 · 5D III for alt and MF lenses: a game changer!


KaaX wrote:
Let's say you print a monochrome blue dot and a monochrome red dot on a sheet of paper. Arrange this sheet of paper perpendicular to the camera and focus on one of the dots. Due to LoCA they can't be both in focus (that is, in the theoretical zero-width focus plane) at the same time. Are there are real lens with LoCA strong enough make the difference between the red focus and the blue focus not fit into the DoF?


You have a better chance of seeing a difference if you include a green dot. I expect to see differences if you use green, far red, and far blue dots. Or better, miniature line patterns instead of dots. Use black paper for ease of interpretation, not white. Still, the presence of spherical aberration may complicate the analysis.

Here you can see an example of how purple fringing, due to longitudinal chromatic aberration, relates to the chromatic correction of the lens:
http://www.imx.nl/photo/optics/optics/chromatic.html



Apr 30, 2012 at 10:18 AM
Light_pilgrim
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p.13 #16 · 5D III for alt and MF lenses: a game changer!


I am glad it is working for you. 85 mm is not the most difficult lens for MF. I was having plenty of problems with 5d mii and zeiss 35 1.4 ze. I photograph people and they move. Af assist was never ever even close to accurate. With eg-s i started learning my own way, but i get tired after some time. I love the result this lens produces....if i hit the focus, but many times i do not.
I think mkiii with this lens is going to be even more difficult and untill it will be a common opinion proven with results that mkiii helps with 35 1.4, i will not upgrade.....for me it is a non starter.


philber wrote:
A few days ago, a thread reported Lloyd Chambers' opinion that manually focusing a 5D III with its viewfinder was a non-starter. That really worried me, since (a) I only use MF lenses (Zeiss), (b) I wear glasses, to correct for a declining eyesight, in line with my age (56), and (c) I use some really difficult glass, since ZE 50P and 85P have focus shift. The icing on the cake is that I am leaving saturday for a major photographic expedition, and lusted for some 5D III goodness, if it proved superior to my 5D II.

I have only had
...Show more



May 25, 2012 at 01:39 PM
Light_pilgrim
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p.13 #17 · 5D III for alt and MF lenses: a game changer!


After reading this thread, i am not convinced. Yes, better AF assist is a help in some cases, but if younphotograph people with 35 1.4 wide open and want to have yes perfectly in focus, af assist is useless. It has to be absoluteley perfect as is normal af with canon equivalent lenses.

There is simply no way you can do portraits like this.....



May 25, 2012 at 01:50 PM
Light_pilgrim
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p.13 #18 · 5D III for alt and MF lenses: a game changer!


The is a world of a difference in terms of how you focus with 85 and 35 1.4 ze.....this zoom vs wa lens. Try tomachieve the same with 35 wide open.

kiddik wrote:
I'm having Siddhu's exact opposite experience, I've never had so many keepers with my ZE 85/1.4 for example. Here's one of my daughter:

http://dl.dropbox.com/u/80257/5D3/klara_85mm.jpg

On the other hand I've had bad experience with AF microadjustments, when I have adjusted at one length another length goes off. I haven't microadjusted any lenses so far on my 5D3, and all are in perfect focus with the Zone AF focusing system.




May 25, 2012 at 02:11 PM
Z250SA
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p.13 #19 · 5D III for alt and MF lenses: a game changer!


philber wrote:
I have only had it a few hours, but here are my early findings. I do not find that the standard VF screen makes it any harder to focus than my 5DII's EG-S.
BUT the much improved AF is a game changer for MF! ... This is so obviously excellent that tomorrow I will do my micro-adjust ... Enjoy!


Finally got mine yesterday, after two months of impatient waiting. I want to thank you, philber, for your once again correct assessment, this time of the AF capability of the 5D3. This IS a game changer. Snap at beep! I just tried it in the garden with the 50MP and 100MP, both wide open. What a difference to the 5D2, and 7D as well!

Thanks to your report I never doubted the sanity of a change from the 2 to the 3.



May 29, 2012 at 09:31 AM
Siddhu
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p.13 #20 · 5D III for alt and MF lenses: a game changer!


I'm going to jump into this discussion to point something out that is a crucial difference between Philber's and Lars's experiences on one side and Light Pilgrim's position (which I agree with):

Light Pilgrim is specifically speaking about shooting with the 35 f/1.4 wide open in a fast moving reportage/portrait style

Shooting static objects at f1.8, f2, or above, is not at all comparable. When I was testing the 5D3 with my ZE's, as soon as my aperture was above f2, the keeper rate was almost comparable to my old school shooting style of just using a VF.

The moment my 35 f1.4 was wide open, the keeper rate was practically non-existant compared to my 90% plus keepers (in terms of focus) with the 5D2 with the EG-S screen.

Arguing with Light Pilgrim about the suitability of the 5D3 for his style of shooting is pointless since shooting static objects stopped down, or even static object wide open is completely different.

It's obvious that there is, and/or there potentially can be an issue with the 5D3 and the ZE 35 f1.4 when shooting dynamic subjects wide open since two separate shooters are reporting the identical problem(s).

So I say to the naysayers who say that this is due to us being luddites, inexperienced, not wanting to learn technology or cheap i.e go out and buy a 1Dx body (Yeah, I'm talking to you Lars), spend a few days shooting in our style with the 35 f1.4 wide open, and then report back as to what was your keeper rate using the AF confirm on the 5D3.

BTW; Why would we go out of our way to trash the 5D3? I was ready to buy a 5D3, but since my experience using the 5D3 for my style of shooting, I repeat MY style of shooting was abysmal, I've held off. Yes it works fine above f2 with my 100mm Makro Planar, my Summicron R, and the 35 1.4 stopped down, but for my favourite way of shooting, my preferred subject matter, it's does not work for ME.



May 29, 2012 at 09:54 AM
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