Yoshizen's Blog

Leitz 50 mm-vs-Zeiss 55 mm

Casually I called Leitz Elmarit lens I used on the Nikon Z in the previous post, a homemade though, glass itself was a serious Leitz product. Hence, having a proper optical quality as we expect. —– ? was it ? = was that quality, within a normal standard ?

—– So, I made a comparizon.

This is the test image taken by the Leitz Elmarit P 50 mm F2.8 at F2.8. With the focus peaking. (Photo right was a part enlargement of the centre = the top of the tree) —– the small twig still maintain its detail though, is this fuzziness normal ?

So, to have a close comparizon, Zeiss Sonner FE 55 mm F1.8 lens was mounted to the same Nikon Z7 body and had the test shot on the same tree, same condition. (since Zeiss / Sony lens has a funny habit = keep move the focus, so that, click the shutter when focus was peaked) In the photo right, some leaves on the tree were coloured red = may be an effect of the chromatic aberration. Was it ? Wait a moment = this is not a £1 junk projection lens but a genuine Zeiss / Sony lens costed hundreds of the pounds. (Even though it was made in Thailand)

Then, I gave yet another test = Zeiss Sonner lens was mounted on the Sony A7R body and had exposure of F1.8 and F8. (manual focus) —– F1.8 image (photo above middle) was the sharpest among all the photos in this post. (Though, strangely F8 image = photo right, was soft —– very difficult to make a precise manual focus on this A7R camera)

Since the same Zeiss lens showed no chromatic aberration on the A7R body here, there is a possibility of either (1) Sony has correction program built into their image processor to compensate lens’s own aberration. or (2) The lens’s obstruction = keep moves its focus when the lens was not mounted on the Sony body = moves only a small part of lens, only to destruct the clear image, hence making big chromatic aberration on the Nikon Z body.

Yet those photos here showed very different strory. The photos were taken same as those photos above.

= Zeiss lens on the Sony A7R body. Exposed on F1.8 and F8. —– But here, F1.8 image (photo middle) showed funny chromatic aberration (red leaves)

(This is the puzzle = how those red leaves were created ? The Sony camera and their image processor seemed to hide too many puzzles.)

—– the correction program of Sony Image Processor may be working erratic. (still, how to make only some leaves red on the Nikon Z and on the Sony A7R as well looks too strange = In fact, the culprit mast be the Lens, not the camera, though, how this Zeiss FE lens can put the red color to a selected part of the image ? === this phenomenon needs to be investigated further !

This is a problem of the “Soft controled digital imaging” = it would make a pretty picture though, it may work, may not work like a Beauty App. That why I hate those artificial images. (Still, film photography can create strange phenomena too —– but, as I didn’t have an experience to enlarge a 35 mm color photo to 1.5 m big and examin the details, may be I was not aware )

Here, they are the shot to finish-off this argument (of Red Leaves) made by Zeiss Sonner 55 mm ZE lens. = The lens was tested at F1.8 if it showes chromatic aberration of red and green fringe on the roof pattern. = The result was as you see. (When the lens was fore-focused, the image has green fringe — photo above right)

And I found a very interesting bokeh pattern on the tree behind. The question is, is this the quarity of the lens which says “Sony / Zeiss Sonner” ? ? ? ( 55 mm is not special, neither F1.8 is difficult to design)

So, how about the chromatic aberration of the Nikon 50 mm F1.2 (photo middle) and F2.8 (photo right) —– a lots of red leaves seems to be here too ! = We shouldn’t be surprised. —– Otherwise we need to pay thousands of £ for a lens which shows no aberration on fully opened iris. === Only the question IS, why we need such perfect image ? ? ? (May be the obsession.) = If you want to see the perfect image, come down to the tree and see it close)

The reason why we don’t see such Chromatic aberration everyday, —– (1) We don’t use maximum F-aperture often, except in the very dark situation. And if it was dark, we can’t see such color fringe in the dark details. (2) In those lenses (Zeiss 55 mm, Nikkor 50 mm) when we stop down two or three stops, the aberration would be disappeared = hence we don’t became aware its existence. (3) We don’t enlarge the image to such big size. = so that, in the small print, the color fringe (even if it’s there) would be buried in the details. (If you are seeing the enlarged tree top photos in this post on a PC screen, it is the equivalent of seeing a 36×24 mm size photo enlarged to the 120 cm x 80 cm (43″x32″) and giving a close look.

The aberration is an optical phenomena, when the light was not converged into the focal point and spread to the surroundings as well, make the image fuzzy. Among the cause of such problem, if it was coused by the way how the light was bend differently by its color (= wave length) it was called Chromatic Aberration. As you might remember to see the rainbow 7 colors made by a prisome, when the light go through the glass they bend according to the wave length (= color). To solve this problem, converging lens which bend the red light more to outward and the diverging lens which bend the blue light more to outward were combined together to conpensate each other to the light concentrate to the same focal point (so to make a sharp picture). —– While making the light bend inward and outward, still make them to converge to the same focal point, optical designer use the fancy technique and special glass etc etc = that’s why good lens is using 10 or more glasses inside of one lens. (= making such lens hugely expensive) —– Sigh 😀

—– Still, it is rather rare to see such prominent Chromatic Aberration like the red leaves here, —– in most of the case, the fringe color appeared only on the edge of the details and make the picture just a bit soft. (Hence the most of the people doesn’t became aware such things ever existed in his lens. )

And in this point, why the Leitz projection lens I’ve talked on the begining of this post showed such character become clear, = the projection lens showes the 35 mm slide image hugely enlarged therefore the chromatic aberration would become quite visible yet, a bit soft image wouldn’t be much of the trouble as the larger the projected image, people view it from the larger distance.

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It seems, the battle between the camera, lens keep going on. 😀

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