Ugly Hedgehog - Photography Forum
Home Active Topics Newest Pictures Search Login Register
Main Photography Discussion
Perspective is changed with different lenses
Page <<first <prev 6 of 22 next> last>>
Aug 21, 2018 22:22:58   #
Grahame Loc: Fiji
 
artBob wrote:
Looks great.
I wonder why you are the only one able to achieve that. Perhaps if you set the overlying transparency at 50% we could better access the results. Even so, I notice some anomalies, the changing paint on the railings, some off-kilter pixels on the top pic (plants on either side of the leftmost post, strangely fat near upright posts, and a few others. Transparency would help, as would being told that you transformed the top shot keeping its ratio, not distorting it at all. Why not post both shots so we all can tell? It's just strange that you are the only one who managed to do this, and scientific inquiry demands repeatability of experiment.
Looks great. br I wonder why you are the only one ... (show quote)


I have seen others do exactly the same previously Bob in their efforts to show what actually happens.

As for the anomalies, disregard the failing wood treatment and concentrate on points where the two frames meet. The images were aligned with lower opacity on the smaller frame and of course the ratio was maintained throughout equalising re-sizing. The subject was chosen specifically because you could 'clearly' see points, bolts, powerline insulators to use to for sizing.

There are obvious very minor anomalies that can be seen, pole edge alignment, power line edge alignment and I put these down to two reasons, a) the fact that manual alignment has to cater for horizontal & vertical movement as well as expansion (diagonal movement) which become difficult with the images expanded on screen. b) that my 28-75 varies in distortion between the range. For info I did not use 'lens distortion correction'.

As for greenery, take no notice of any because it is breezy here.
I can happily post the original shots, but then anyone could say that the result achieved was luck because of distortion in my lens.

Reply
Aug 21, 2018 22:31:55   #
artBob Loc: Near Chicago
 
TriX wrote:
Now you have your “proof” and the only thing you can pick at are a few pixels likely caused by simple lens distortions. And you want more of the same? When will you have the grace (and intellect) to simply admit you are simply mistaken? You would gain a great deal more credibility than endlessly pursuing this lost cause. It’s not so hard, everyone here, certainly including myself, makes mistaken assertions often, and when we do, we admit our mistake(s), learn from them, and move on.


Bless your heart! I guess you don't know me, as I often do make mistakes and acknowledge them, But then, if you acknowledged that, you wouldn't have any way to avoid simply being transparent. Now I really do think you faked it, because a truly searching person would not mind at all sharing their data. You and Andy (the now science guy) don't seem to grasp science or epistemology at all.

Since you can't back up your assertion (as I have done in my posts, sharing all aspect of each shot and inviting others to check them out), your assertion is worthless. Your deflection is a fail. You have proven nothing because your data is tainted and your on't allow your experiment to be replicated.

Reply
Aug 21, 2018 22:45:27   #
artBob Loc: Near Chicago
 
Grahame wrote:
I have seen others do exactly the same previously Bob in their efforts to show what actually happens.

As for the anomalies, disregard the failing wood treatment and concentrate on points where the two frames meet. The images were aligned with lower opacity on the smaller frame and of course the ratio was maintained throughout equalising re-sizing. The subject was chosen specifically because you could 'clearly' see points, bolts, powerline insulators to use to for sizing.

There are obvious very minor anomalies that can be seen, pole edge alignment, power line edge alignment and I put these down to two reasons, a) the fact that manual alignment has to cater for horizontal & vertical movement as well as expansion (diagonal movement) which become difficult with the images expanded on screen. b) that my 28-75 varies in distortion between the range. For info I did not use 'lens distortion correction'.

As for greenery, take no notice of any because it is breezy here.
I can happily post the original shots, but then anyone could say that the result achieved was luck because of distortion in my lens.
I have seen others do exactly the same previously ... (show quote)


Thank you.
So...a mystery. All other similar attempts, by me and others, have shown discrepancies in linear perspective. I dunno. Maybe, as with my shots, they used different lenses and you used one zoom?

Again,thanks for taking the time and sharing. If you don't mind posting the pix, I would like to experiment with them. Also, please let me know if you used just one, zoom lens. (Oh, and hope the ankle-biters don't get ankley. :-))

Reply
 
 
Aug 21, 2018 22:53:13   #
TriX Loc: Raleigh, NC
 
artBob wrote:
Bless your heart! I guess you don't know me, as I often do make mistakes and acknowledge them, But then, if you acknowledged that, you wouldn't have any way to avoid simply being transparent. Now I really do think you faked it, because a truly searching person would not mind at all sharing their data. You and Andy (the now science guy) don't seem to grasp science or epistemology at all.

Since you can't back up your assertion (as I have done in my posts, sharing all aspect of each shot and inviting others to check them out), your assertion is worthless. Your deflection is a fail. You have proven nothing because your data is tainted and your on't allow your experiment to be replicated.
Bless your heart! I guess you don't know me, as I ... (show quote)


I have zero intention of wasting time either digging out old shots or creating new ones to prove (again) which has already been demonstrated - you have had your “proof” both visually from multiple sources and from experts, and now I think you’re just being disingenuous and wasting every one’s time for your own misguided enjoyment. No rationional (and I emphasize rational) person can continue to assert this crap in the face of 18 pages of pros telling you you’re wrong. Hopefully, no beginners (or students) who read this idiocy believe it. I have tried to be polite, but there comes a time when you need to be labeled for what you’ve proven to be - a time waster and a fake. I don’t think you’ll get by with this BS again any time soon. You’ve squandered any credibility you had, and I for one (and I’m sure many others) won’t waste our time with you again.

Reply
Aug 21, 2018 23:06:55   #
artBob Loc: Near Chicago
 
TriX wrote:
I have zero intention of wasting time either digging out old shots or creating new ones to prove (again) which has already been demonstrated - you have had your “proof” both visually from multiple sources and from experts, and now I think you’re just being disingenuous and wasting every one’s time for your own misguided enjoyment. No rationional (and I emphasize rational) person can continue to assert this crap in the face of 18 pages of pros telling you you’re wrong. Hopefully, no beginners (or students) who read this idiocy believe it. I have tried to be polite, but there comes a time when you need to be labeled for what you’ve proven to be - a time waster and a fake. I don’t think you’ll get by with this BS again any time soon. You’ve squandered any credibility you had, and I for one (and I’m sure many others) won’t waste our time with you again.
I have zero intention of wasting time either diggi... (show quote)


Well, you lie, for starters, when you write, "...you have had your “proof” both visually from multiple sources and from experts." There is only one proof posted, real photos stacked as called for in an honest verification. Since you believe some experts without verifying for yourself, you might consider joining some cult.

Since, as you write, "Hopefully, no beginners (or students) who read this idiocy believe it. I have tried to be polite, but there comes a time when you need to be labeled for what you’ve proven to be - a time waster and a fake," I would just be either wasting your time or faking it if I told you that I have had thousands of student evaluations. Sadly only some tens have been negative. But then, obviously none of them were as perceptive as you. Most were more truly polite.

Finally, I am happy to discover I've "squandered any credibility [I] had, and [you] for one..won’t waste our time with you again." This should save you the pain of having to actually prove something, and me the pain of confronting one of the most recalcitrant learners I'v ever had.

Reply
Aug 21, 2018 23:13:52   #
Grahame Loc: Fiji
 
artBob wrote:
Thank you.
So...a mystery. All other similar attempts, by me and others, have shown discrepancies in linear perspective. I dunno. Maybe, as with my shots, they used different lenses and you used one zoom?

Again,thanks for taking the time and sharing. If you don't mind posting the pix, I would like to experiment with them. Also, please let me know if you used just one, zoom lens. (Oh, and hope the ankle-biters don't get ankley. :-))


Different lenses are going to have different distortions, whether primes or zooms. Changing lenses adds to the possibility of alignment change (slight movement of tripod). As mentioned in the post, I used the 28-75mm zoom, it was a Tamron.

It would be interesting to see what the results are using 'lens correction profile' as opposed to not using it, I suspect a noticeable difference.

Here are the two images, 28mm & 75mm


(Download)


(Download)

Reply
Aug 21, 2018 23:33:14   #
artBob Loc: Near Chicago
 
Grahame wrote:
Different lenses are going to have different distortions, whether primes or zooms. Changing lenses adds to the possibility of alignment change (slight movement of tripod). As mentioned in the post, I used the 28-75mm zoom, it was a Tamron.

It would be interesting to see what the results are using 'lens correction profile' as opposed to not using it, I suspect a noticeable difference.

Here are the two images, 28mm & 75mm

I am SO confused. I uploaded your pix. Made the 75mm a 50% transparency layer in Photoshop. Lined it up as exactly as I could, matching the top of the near post. And this is what I got! Aside from that post, the blurs show where the perspective has been distorted.

Any idea?


(Download)

Reply
 
 
Aug 21, 2018 23:53:25   #
Grahame Loc: Fiji
 
Yes, you have clearly not aligned them properly. It takes considerable work to adjust both 'physical position' plus 'enlargement' of the image you are placing within the other. You will need to go down to pixel level at times.

Here's another set of two shots, 28 & 75 mm taken with the same lens. Note that the opacity of the 75mm layer I am inserting is set at 50%. Whilst I align I concentrate on two points, in this case the top of the stink pipe and the street light. Again it is windy so take no notice of greenery.

I would suggest any minor anomalies are due entirely to lens distortion, possibly wind on the power lines, or that I could have got it better if I had spent more time on it. To suggest what this may show is a "perspective" change would really be grasping at straws.


(Download)

Reply
Aug 22, 2018 00:19:20   #
Grahame Loc: Fiji
 
artBob wrote:
Aside from that post, the blurs show where the perspective has been distorted.


This statement makes absolutely no sense with respect to 'perspective'.

The 'blur' simply shows where two images of two different sizes and different alignment composed together make the result "blurry".

Reply
Aug 22, 2018 00:43:23   #
artBob Loc: Near Chicago
 
Grahame wrote:
Aside from that post, the blurs show where the perspective has been distorted.


This statement makes absolutely no sense with respect to 'perspective'.

The 'blur' simply shows where two images of two different sizes and different alignment composed together make the result "blurry".[/quote]

Actually, perspective lines fall along edges, so: two different perspectives and sets of vanishing points, red for wide angle, blue for tele.

Once again, perspective IS distorted by different focal lengths. While it is sometimes hard to detect it is there, and sometimes it creates problems.

By the way, the vanishing points for the tele show that you tilted the camera a bit.

Thanks for the shots. May I come visit you on your lovely porch some day? ;-)


(Download)

Reply
Aug 22, 2018 02:51:15   #
Grahame Loc: Fiji
 
artBob wrote:
By the way, the vanishing points for the tele show that you tilted the camera a bit.


Really ?

I can only assume you have made that assumption based upon the 'accuracy' of the red and blue lines you placed on your attempt to align my two images.

Out of interest, what is the red line that I have pointed out below supposed to be aligned with Bob?


(Download)

Reply
 
 
Aug 22, 2018 03:26:07   #
selmslie Loc: Fernandina Beach, FL, USA
 
artBob wrote:
You prove my point. Perhaps you do not notice a difference, and perhaps that is the problem with many here. I saw it. So, I superimposed the two ice chests, lining up the upper left corner (any spot would do) and voila! The perspective is different.

You can see that, right?

No, we can clearly see that you have once more proven everyone else's point - that the perspective did not change because the edges of the two images are parallel.


Your problems are obvious:
- You don't know the meaning of perspective.
- You don't know how to resize to get the images to match.
- You don't have sense enough to not post an image that disproves your claim.
- You don't understand distortion.
- You don't understand geometry. That't not a character flaw but pretending that you understand it does not fool anyone.
- You claim that anyone who does not agree with you is wrong.
- You can't find a way to get out of the hole you have dug yourself into.
- You are willing to lie.
- You insult people who disagree with you.
- Everyone else has been right all along and you have been wrong.

Several of those problems could be accompanied by a suitable pejorative but I will leave it to the reader to supply their own.

Reply
Aug 22, 2018 03:27:51   #
selmslie Loc: Fernandina Beach, FL, USA
 
artBob wrote:
I am SO confused. ... Any idea?

It has all been explained to you repeatedly. Yet you are still confused? There is something seriously wrong with you!

Reply
Aug 22, 2018 04:49:52   #
Grahame Loc: Fiji
 
artBob wrote:
Once again, perspective IS distorted by different focal lengths. While it is sometimes hard to detect it is there, and sometimes it creates problems.


My final one on this I think............

It was stated within this thread and another that if you use two different focal lengths from the 'same' camera/subject distance the 'perspective' would change. Let's forget the word 'perspective' for a minute and consider another critical 'suggestion' that was made; "You can not superimpose one image taken at one focal length onto another when taken from the same position as the perspectives will be different", I say as well as others, you can.

You have attempted to use my images to disprove this fact, but I have clearly shown your 'technical' method is extremely poor and flawed. Why is it flawed, your lines don't line up with anything credible.

Above you mention "While it is sometimes hard to detect it is there, and sometimes it creates problems".

So here's my last example for you, I tried to find a 'worse case scenario'. I will agree with one thing you have said, "it is sometimes hard to detect", although I would have said just about totally impossible unless you have a method of ensuring 100% that lens distortion is not present at all.

Point a) 720m from camera. Point b) 4900m from camera. Point c) 3.5m from camera. Note the buildings directly under the a, and b,. And for info this time I used lens profile correction in ACR.


(Download)

Reply
Aug 22, 2018 05:47:29   #
wdross Loc: Castle Rock, Colorado
 
artBob wrote:
In the topic "Does perspective change when you change the focal length?" I was not allowed to reply.
Here's what I wanted to write:
"What bigotry and ignorance. I used Andy's own photos (can be seen towards end of "Does perspective change when you change the focal length?", and AGAIN showed that he and others who deny that focal length changes perspective are wrong. Since scientific experimentation and free speech have been shut down here, I am going to post my response to Andy and the original poster who banned me, in my own topic."
I also would like to tell some of the people on that thread the following, in case they follow here:
"Please stop calling people names, for it shows the weakness of your argument.
"Please stop calling people ignorant. In this case, apparent ignorance of linear perspective on the part of some called into question extensive knowledge on my part--I had to teach the damn stuff. Tough. I know many people cannot perceive it, fail at it. However, to accuse of ignorance actually reveals ignorance."

So, here is a transparency of both Andy's photos, with perspective lines indicated. The perspective is indeed changed. I'll also upload his photos, so others can explore.

Also, I found a stock photo shot by a wide angle lens, and drew the perspective lines on it. They are all over the place, thus false. I then corrected for the lens in Photoshop, and indicated the perspective lines we (and generally a 50-70mm lens sees) see.

Finally, CaptainC, whose post started the whole discussion, posted four photos, all shot from the same place, same distance, on a tripod. He had said those who thought lenses distorted perspective were wrong, and that could be proven by cropping the shorter length lens photo and overlaying it on a tele photo. I did that, because I thought, "Wow, really? That goes against what I had thought." So, I looked at two of those photos, lining up the same, most distant building in each so they matched, and found that perspective indeed had changed. Perspective lines for each shot, one set blue, one set red are overlaid.

If anyone wants to join in the discussion, with insight and honesty, please do. Mysteries remain.
In the topic "Does perspective change when yo... (show quote)


Did anyone compensate for the movement of the nodule point of the lense? That will cause a zoom lense to "move" even when the tripod doesn't. The perspective will not change if it is based off the nodule point. The nodule point is also important when one wants a perfect panoramic. If one does not rotate the camera around the specific nodule point of the particular focus length being used of the zoom lens, there will be a shift of very close objects such that they do not and will not superimpose without sofware manipulation. That nodule point changes relative to the tripod mount with every zoom movement of the lense. If these pictures that artBob compared were not done from the nodule point, yes, the perspective did change.

Try a set of slides or images done off the nodule point instead of the tripod mount. The perspective will not change.

Reply
Page <<first <prev 6 of 22 next> last>>
If you want to reply, then register here. Registration is free and your account is created instantly, so you can post right away.
Main Photography Discussion
UglyHedgehog.com - Forum
Copyright 2011-2024 Ugly Hedgehog, Inc.