wickerprints wrote:

No, no, no. This is a categorically incorrect interpretation of focal length.

I never said anything about focal length being longer...
I know you think I'm whack, but please give me a little credit for not being a total moron.

The oly is physically 31mm long, the TSE is physically 107mm long ... that's physically 76mm longer, which yields a different working distance when the film plane/camera position remains constant.

I've assumed nothing. I've simply done exactly as I stated ... i.e. shot two different lenses from the same shooting position and recorded the results ... nothing less, nothing more. Upon realizing that the PHYSICAL length of the two lenses is different enough that it impacts the perspective, I've indicated a re-shoot is warranted.

The question was asked why it showed two different position/perspectives. The answer is simply that one lens is three inches longer than the other and thereby, while shot from the exact same film plane/camera position, the working distances are different and have yielded a different perspective.

Would you prefer I equalize the AOV or the working distance for the re-shoot?
I realize that no matter what I do you're going to criticize the integrity of it, so I'm wondering why I should even bother.

wickerprints wrote:

No, no, no. This is a categorically incorrect interpretation of focal length.

RustyBug wrote:
I never said anything about focal length being longer...
I know you think I'm whack, but please give me a little credit for not being a total moron.

The oly is physically 31mm long, the TSE is physically 107mm long ... that's physically 76mm longer, which yields a different working distance when the film plane/camera position remains constant.

I've assumed nothing. I've simply done exactly as I stated ... i.e. shot two different lenses from the same shooting position and recorded the results ... nothing less, nothing more. Upon realizing that the PHYSICAL length of the two lenses is different enough that it impacts the perspective, I've indicated a re-shoot is warranted.

And what I tried to explain to you is that the physical length of the lens does not affect the perspective. It is the distance from the object to the plane of focus (i.e., the sensor) that affects the perspective.

You seem to be under the misapprehension that the difference in the field of view between the two images is due to the larger size of one lens. And what I am telling you is that this belief is entirely false.

The question was asked why it showed two different position/perspectives. The answer is simply that one lens is three inches longer than the other and thereby, while shot from the exact same film plane/camera position, the working distances are different and have yielded a different perspective.

NO. This is incorrect, as I explained in my previous post. The working distance does not relate to perspective; it is the SUBJECT distance--the distance from the focal plane to the object in focus--that relates to the perspective. Because, as you claim, the camera body was not moved between lens changes, the conclusion is that the focal length of the system could not be the same if the resultant framing from each lens is different. The difference in framing has nothing to do with one lens being larger than the other. I cannot stress this enough.

Would you prefer I equalize the AOV or the working distance for the re-shoot?
I realize that no matter what I do you're going to criticize the integrity of it, so I'm wondering why I should even bother.


I am unconcerned with the question of whether to equalize the framing. I don't even care about which lens is sharper. I am not here to question the integrity of your testing methodology. I am merely correcting what I consider to be your misunderstanding of certain optical concepts, so that should you care to gain a better understanding of the theory, the information is there for you to learn. It is entirely up to you whether or not you want to accept it or not.

Not to get sidetracked, but to address comments from @SKumar25 @Lars Johnsson:

The problem isn't a bad copy of a lens, or a screwed up camera. The problem is that manufacturing tolerances create a situation where wide angle lenses are often not optimally sharp across the frame on high megapixel full frame cameras. This problem is particularly exacerbated by wide angle lenses. Read Roger Cicala's article for an excellent overview of the problem: http://www.lensrentals.com/blog/2010/03/this-lens-is-soft-and-other-facts

wickerprints wrote:
The working distance does not relate to perspective.

Ummm ...

Mr Joe wrote:
Not to get sidetracked, but to address comments from @SKumar25 @Lars Johnsson:

The problem isn't a bad copy of a lens, or a screwed up camera. The problem is that manufacturing tolerances create a situation where wide angle lenses are often not optimally sharp across the frame on high megapixel full frame cameras. This problem is particularly exacerbated by wide angle lenses. Read Roger Cicala's article for an excellent overview of the problem: http://www.lensrentals.com/blog/2010/03/this-lens-is-soft-and-other-facts


I can agree to a certain degree of what you are saying, but I also think you are exagerating the "bad copy" problem a lot. It's not normal to get 4 bad copies when testing 5 lenses like you did in your link.
And the bad copy problem has nothing to do with the original comment about "the $1500-2000 lenses from Canon and Zeiss can't maintain edge-to-edge sharpness" as good as Oly lenses.
We only compare good copies from all 3 brands of course......

I have been reading Roger C articles. And digilloyd have similar articles about wide angle lenses

wickerprints wrote:
And what I tried to explain to you is that the physical length of the lens does not affect the perspective. It is the distance from the object to the plane of focus (i.e., the sensor) that affects the perspective.

You seem to be under the misapprehension that the difference in the field of view between the two images is due to the larger size of one lens. And what I am telling you is that this belief is entirely false.

The question was asked why it showed two different position/perspectives. The answer is simply that one lens is three inches longer than the other and thereby, while shot from the exact same film plane/camera position, the working distances are different and have yielded a different perspective.

NO. This is incorrect, as I explained in my previous post. The working distance does not relate to perspective; it is the SUBJECT distance--the distance from the focal plane to the object in focus--that relates to the perspective. Because, as you claim, the camera body was not moved between lens changes, the conclusion is that the focal length of the system could not be the same if the resultant framing from each lens is different. The difference in framing has nothing to do with one lens being larger than the other. I cannot stress this enough.

Uuhhm ....

Perspective is determined by the position of the entrance pupil of the lens. The subject distance is the distance from the subject to the front principal plane of the lens. A change of lens can alter both, regardless of possible changes of the focal length.

Wow, what happened here? I wake up and see that the images have been removed.

It was very easy to see in the full images that not only the framing was different, but also the relative position in the frame between foreground and background objects, hence the perspective must have been changed.

I asked if there was any idea behind this, and have found the answer in a quote that it was not intentional, and that the same camera position was used. Thanks for the answer!

Toothwalker wrote:Uuhhm ....

Perspective is determined by the position of the entrance pupil of the lens. The subject distance is the distance from the subject to the front principal plane of the lens. A change of lens can alter both, regardless of possible changes of the focal length.



Thank you ... someone who actually knows what they are talking about ... yet more importantly, actually READS and THINKS about what was written before casting boulders of superiority and ineptness. I know I struggle at times using proper technical terminology, but I do have a "small clue" at what's going on here.

The build of a TS-E with its additional movements of T&S between the film plane and the entrance pupil (and the front principal plane) places them both closer to the subject than that of a 'conventional' similar focal length lens, although the film plane/camera position remained exactly the same (not simply "claimed"). Despite the rhetoric suggesting of my inept understanding of optical theory, the gross insistence that perspective is dependent upon the film plane position and independent of the optics involved suggests otherwise.

When I get "untorqued", I'll do a re-shoot. If any one would like to objectively suggest how I construct the re-shoot in such a way that my "ineptness" doesn't impede the value of such a comparison ... owing to the PHYSICAL AND OPTICAL differences of a T&S vs. conventional, I'll try to accommodate such objectivity into the re-shoot, i.e. should I align the entrance pupil, front plane, or AOV as the methodology for constructing an 'equitable' comparison. We've obviously seen that the 'film plane' is NOT (although typical) the appropriate methodology for constructing such an equitable comp between the T&S vs. conventional ... so what is?

Thanks for your input regarding this matter.

Toothwalker wrote:
Perspective is determined by the position of the entrance pupil of the lens. The subject distance is the distance from the subject to the front principal plane of the lens. A change of lens can alter both, regardless of possible changes of the focal length.

+1

alundeb wrote:
Wow, what happened here? I wake up and see that the images have been removed.

It was very easy to see in the full images that not only the framing was different, but also the relative position in the frame between foreground and background objects, hence the perspective must have been changed.

I asked if there was any idea behind this, and have found the answer in a quote that it was not intentional, and that the same camera position was used. Thanks for the answer!


Yes, you were absolutely correct that the perspective was different between the two. I did not account for the physical and optical variance between the two lenses when I used the "same film plane" as the methodology for comparison. Thanks for your question and allowing for my answer. I will try & re-shoot and re-post in the upcoming days.

Hey Rusty, regardless of the technical "error" I thought it was a splendid comparison.

Thanks John,

Well, if you are "backed up against the wall", it still accurately represents the difference that the two lenses would yield shooting from the same film plane. But, since I can reposition them, I'll try to do so such that it seems more 'equitable' once I figure out which approach I should take on Round 2 ... i.e. entrance pupil, front plane, AOV, framing (or other ??).

For Round 2 I'll set up on my pano/focusing rail head, so that I can reposition accurately. I was just using my ball head (unmoved) for these and even though I tried to reposition the tripod ... ummm, I'll have better results by using my geared (and incrementally marked) rail.

FYI, given the difficulty in obtaining "exactly" the same focus at distant points using WA, I chose to use the near (yet not @ mfd) subject distance to provide for a more precise focus comp. Also, I like using wides for foreshortening, so it is important to me to see how a WA handles the closer objects.

Thanks for your efforts, RustyBug.

I appreciate your comparison. I'm astonished by the OM 24's image "quality". Never thought my little OM 24 could rival the lens I'm planning to purchase...

Enjoy,
Sten

The way-above-my-paygrade discussions notwithstanding, for we-the-paltry this is an insightful comparison. The technos talk about everything except the quality of the image.

I remember doing a similar comparison several years back with an Oly 200 f4 vs a Canon 180 macro, going through the agony of getting the framing to match, and comparing bits and pieces of two sets of images. Now, as we all know, the 200 f4 is not a top- or second-top tier performer like the 180 macro. The images were almost indistinguishable from each other. The result was that the highly-regarded 180 commanded an equally highly-regarded price in the resale market and I ended up with an armada of Olys (24, 80 macro, 135 macro, 85 f2) and a bellows.

I could be wrong here, but it looks to my eye like the Oly is every bit the equal of the TS-E, without the tilt/shift. Thx, Kent.

Thanks Sten & David.

Yes, it is a bit "shocking" to see how the Oly performed, but one must also understand that the TS-E is shooting with its optics farther from the film plane by virtue of the T&S movements between the film plane and the optical elements (akin to inserting a tube) and the subsequently larger image circle projection.

I remember pouring through mounds of info (16:9 24mm shootout, etc.) before picking up the Oly 24/2.8 as my first alt (owing to Canon's lack of a good WA at the time) a few years back. The reports of it being really good were well noted, but even still, seeing this does make one re-appreciate it as a little gem (for the price of a rhinestone). I haven't shot my Oly 24/2.8 for quite a while (usually grabbing the 28/3.5 or 21/3.5 instead) so I'd somewhat forgotten just how good it is for a WA.

My point for the comp was to be able to scrutinize the variances of the TS-E, but the reminder @ the Oly is just icing.

RustyBug wrote:
When I get "untorqued", I'll do a re-shoot. If any one would like to objectively suggest how I construct the re-shoot in such a way that my "ineptness" doesn't impede the value of such a comparison ... owing to the PHYSICAL AND OPTICAL differences of a T&S vs. conventional, I'll try to accommodate such objectivity into the re-shoot, i.e. should I align the entrance pupil, front plane, or AOV as the methodology for constructing an 'equitable' comparison.

It depends on whether you want to compare images with the same perspective or the same image magnification. Normally there is no need to choose, but in your case with asymmetrical lens designs
at relatively close focus there might be. If you want to compare depth of field and background blur, I suggest to move the camera over a rail along the optical axis until you obtain the same image magnification. That is, the number 5 should have the same size on the sensor with both lenses. The perspective and angle of view can turn out to be different, but should still be in the same ballpark.

Toothwalker wrote:
If you want to compare depth of field and background blur, I suggest to move the camera over a rail along the optical axis until you obtain the same image magnification. That is, the number 5 should have the same size on the sensor with both lenses. The perspective and angle of view can turn out to be different, but should still be in the same ballpark.


Thanks much ... that's what I'll go with for Round 2. Hopefully displaying sufficiently equitable so there's no need for Round 3.

Hey Joe, you should have borrowed my good copy of ze 21 in Ridgecrest when I took your night photography workshop. I think your camera mount must be warped or something or you have extremely bad luck in getting a good copy as I have never seen a zeiss lens peform that badly across the frame.
If you want to meet up sometime in south bay let me know. I have the Zeiss 21,35/2,50/2 and am testing out the new 25/2 today.

Wayne, you beat me to the 'Hey Joe' reference, the disappearance of the images earlier threw off this old Jimi fan!

Pressing on regardless, in reference to our thread within a thread re bad copies, I came across a nice quote re manual focus lenses vs AF lenses and found, not for the first time, a serious reference by a serious individual to issues associated with the paltry lightweight mechanisms used to speed the lens elements on their way up and back down the lens seeking acceptable focus. Long sentence apology. I imagine from the date that the speaker refers to Contax Zeiss:

"These Zeiss lenses are superb as are the Leica R offerings. The manual focus is a plus as AF lenses have to be 'looser' in order to focus with any speed. Therefore they are subject to a tiny bit of de-centering not as present with MF lenses. De-centering is a prime factor in loss of sharpness."

If there is one lens type to avoid buying in the high Mp era, it is an old AF lens of unknown or suspect provenance. And we really should not be seeing alarming levels of bad copies in manual focus lenses, let alone ones that take such a large bite from the wallet. The makers know the lenses now have to be very well assembled and QA'd.

Oh, and do give us whatever feedback on the new 25/2 you feel happy to offer. So far it's a confused picture, and after seeing Roger's disturbing pictures (25/2 vs 21/2.8) recently posted here, I do wonder.

@wayne seltzer - Hey, how's it going? Sounds like Zeiss fever in your camera bag. Zuiko fever is much less expensive.

I'm going to wait until my next camera body before I try again. I could probably shoot 90% of what I do with a Zeiss 18 or 21, and a Zeiss 28 or 35. The question is, which one(s) to pick.

@philip_pj - If I had a quarter for every Hey Joe reference, I could retire early.
And ironically, I have a 24-70/2.8L that's very sharp across the frame on my 5D II (along with a Zuiko 18, 21, and 28).

Again, it's not a bad lens or a bad camera, it's the combination of a lens tolerance that's off one way, with a camera that's off the other way. Both can be within spec, and you still don't have a sharp picture. And my testing showed lenses that were off on the left side, and others that were off on the right side -- with the same body. Yet all of my Oly lenses worked fine with either body.