Author Topic: Tilt/Shift Lens Simulator  (Read 779 times)

garry23

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Tilt/Shift Lens Simulator
« on: November 02, 2020, 03:44:49 PM »
I thought some may be interested in my latest post: http://photography.grayheron.net/2020/11/focusing-tilt-shift-lens.html

garry23

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Re: Tilt/Shift Lens Simulator
« Reply #1 on: November 03, 2020, 12:12:58 PM »
This is the first of a few additional posts I'll be making on TSE lenses and DOFIS:

http://photography.grayheron.net/2020/11/further-tiltshift-modelling.html

tupp

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Re: Tilt/Shift Lens Simulator
« Reply #2 on: November 04, 2020, 09:48:11 AM »
Interesting tool!  Excellent job!

However, I sense that you might be slightly overthinking things.  Essentially, you are illustrating the Scheimpflug principle, except that you are not really showing the lens plane nor the focal (film/sensor) plane.

Here is a simple drawing showing how those two planes relate to the focus/subject plane.  It does not include the depth of field limits. Here is the travel photography article in which the drawing appears, which includes a passage that explains the Scheimpflug principle and which succinctly describes a common practical technique own how to use tilt/swing to control the plane of focus.

To learn how the Scheimpflug principle works, it is best to just try it with your view camera or tilt/swing lens/adapter.

By the way, I am not sure if the "Focus" slider in your simulation accurately demonstrates the results of actually focusing a view camera or a tilt/swing lens.

Thanks for making the simulation!

garry23

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Re: Tilt/Shift Lens Simulator
« Reply #3 on: November 04, 2020, 10:32:15 AM »
@tupp

This simulator is a tool for DSLR users, ie not for technical camera users ;-)

Also, you don’t need to worry about Scheimpflug if you use the hinge, eg see here http://www.northlight-images.co.uk/using-lens-tilt-on-your-digital-slr/

Bottom line: I wrote TiltSim to help TS-E users explore the basic principles, ahead of going into the field.

Thanks for taking the time to provide feedback: much appreciated.

tupp

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Re: Tilt/Shift Lens Simulator
« Reply #4 on: November 05, 2020, 12:24:22 AM »
This simulator is a tool for DSLR users, ie not for technical camera users ;-)

The Schiempflug principle (and the "hinge" principle) apply to any camera that allows changing the orientation of the lens plane and/or film/sensor plane.  So, it applies to view cameras as well as to DSLRs with tilt/swing lenses and adapters.


Also, you don’t need to worry about Scheimpflug if you use the hinge, eg see here http://www.northlight-images.co.uk/using-lens-tilt-on-your-digital-slr/
Likewise, you don't need to worry about  the "hinge" notion with Scheimpflug.

Furthermore Scheimpflug is simpler and easier, because all of the "planes" in question are tangible:
  • the focal plane is the sensor/film (and often marked on DSLRs);
  • the lens plane is the optical center of the lens;
  • and the focus plane is revealed when objects become sharp.
In contrast, the "hinge" theory is merely a more abstract variant of the Scheimpflug principle, which adds intangible, unseen "planes."

The "front focal plane" of the hinge theory exists in the air, one focal length (the infinity focal length?) from the optical center of the lens.  There is nothing physical to indicate the location of this plane some distance in the air in front of the lens, so it has to be estimated.

In addition, the hinge method adds another somewhat intangible variable with its reliance on the abstract "parallel-to-film" lens plane.  This hypothetical plane intersects the center of the lens, but it runs parallel to the film plane, regardless of how the lens is tilted/swung.  So, using the "parallel-to-film" lens plane requires yet another estimation.

The "front focal plane" estimation and the "parallel-to-film" lens estimation are both unnecessary with the simpler and solid Scheimpflug technique.


Bottom line: I wrote TiltSim to help TS-E users explore the basic principles, ahead of going into the field.
The simulation looks great!  On the other hand, it would be interesting to see such a simulation based on the Scheimpflug principle.

Regardless, the "Scheimpflug" and "hinge" methods along with simulations are no substitute for actually putting the principles to practice and getting a feel for how tilt/swings affect the plane of focus (which is actually simple and straightforward).  One doesn't normally use "math" when using tilts and swings.


Here is the pertinent passage from the travel photography blog (linked above) that might be helpful to a DSLR user who is new to tilt/swing:
Quote from: David Ward
"The usual focusing method using tilt is iterative, there are alternative methods based on measurements and tables but they’re both slower and less accurate. The following is a simplified description of focusing using Scheimpflug with a view camera.

First, one selects two targets on the ground glass (one near and one far along the same plane). A movement is applied (usually tilt in a classic landscape) and the far target focused on. The second target is then scrutinised, using a magnifying loupe on the ground glass, and a small amount of extra movement applied. If the image gets sharper at the second target then you are moving in the right direction, if it gets less sharp then too much tilt has already been applied. Return to the first target, re-focus and repeat until both are in sharp focus.

Care must be taken to apply tilt in small amounts. Don’t be tempted to go straight to sharp focus on the second target. This will mean that both targets cannot be in focus at once.

It must also be remembered that the focusing plane is a flat surface. If your subject is very three-dimensional then movements might not be the answer, it may simply be better to stop down.

The same basic focusing principles apply to T/S lenses on an SLR."


One more thing -- as I mentioned, there might be a problem with the "Focus" slider in your simulation.  It seems to be based on focusing by moving the focal plane (the sensor/film), which is not the way that DSLRs focus.  Focusing a tilt/swing lens on a tripod-mounted DSLR might give different results than what is shown in your simulation.

garry23

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Re: Tilt/Shift Lens Simulator
« Reply #5 on: November 05, 2020, 12:21:58 PM »

garry23

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Re: Tilt/Shift Lens Simulator
« Reply #6 on: November 05, 2020, 03:53:47 PM »
@tupp

Once again, thanks for all your feedback.

Bluntly, I think you are looking for more than I was attempting to do here, ie your references are sound for a large format or medium format technical camera user.

For a TS lens on a Dslr, I’m comfortable that TiltSim is doing its job, ie as an tool to help one understand a tilt and shift lens on an Dslr ;-)

Hopefully, my latest post explains my thinking.

Cheers

Garry

tupp

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Re: Tilt/Shift Lens Simulator
« Reply #7 on: November 08, 2020, 03:32:36 AM »
Quote
your references are sound for a large format or medium format technical camera user.
Again, the Scheimpflug Principle and the "hinge" theory apply equally to all cameras that that allow changing the orientation of the lens plane and/or film/sensor plane.

However, the Scheimpflug principle is more sound and uses tangible variables, unlike the Hinge theory, which requires one to estimate two planes that exist "in the air," some distance from their reference planes.

By the way, I think that instead of the term "technical camera" you actually mean "view camera."  On a view camera, the front and rear standards have tilt/swing/shift.  On a technical camera, only the front standard has tilt/swing/shift, much like a DSLR with a tilt/swing/shift lens/adapter.


Quote
For a TS lens on a Dslr, I’m comfortable that TiltSim is doing its job, ie as an tool to help one understand a tilt and shift lens on an Dslr
Okay, but your focus slider reflects the action of moving the rear standard of a view camera -- not focusing a tilt/shift lens on a DSLR.

Here is a GIF (from the article you linked above) that matches the results of your focus slider:


Please note how the example shows a view camera, and please observe that the "hinge line," the "parallel-to-film lens plane" and the "front focal plane" remain stationary while the rear standard of the view camera moves.

That is not how a DSLR with a tilt/swing lens works. With a DSLR, the the tilt/swing lens moves -- along with  the "hinge line," the "parallel-to-film lens plane" and the "front focal plane."

Also, it might be clearer if the "SelectN = 8" slider was labeled "aperture" and it would be helpful if that slider gave normal f-numbers.

garry23

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Re: Tilt/Shift Lens Simulator
« Reply #8 on: November 08, 2020, 07:54:18 AM »
@tupp

Fully understand all you have said and I assure you I know what you are referencing.

As I keep on trying to say to you, the current TiltSim is a simplified model to gain some insight into TS lenses.

Your gif is well known on the web, but you could also have shown the gif showing the hinge in action from front tilt, ie see both here http://www.northlight-images.co.uk/using-lens-tilt-on-your-digital-slr/

All I’m doing in TiltSim is showing the hinge, ie not the Scheimpflug line. That is exploiting the J height from sin tilt = f/J and, of course, focus distance.

I will likely write a 2nd version which better models  the true lens tilt, but it will not change the gross view of things.

Once again, thanks for posting a reply, but I can assure you I know TiltSim is ‘wrong’ ;-), but not so wrong that it’s not useful.

Cheers

Garry

Ps SelectN is used because of how Desmos works. It does select the 1/3 stop aperture numbers, which are shown on the y axis ;-)

tupp

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Re: Tilt/Shift Lens Simulator
« Reply #9 on: November 08, 2020, 09:11:19 AM »
Your gif is well known on the web,...
I stated parenthetically that it came from the article that you linked above.  Did you catch that?


...but you could also have shown the gif showing the hinge in action from front tilt, ie see both here http://www.northlight-images.co.uk/using-lens-tilt-on-your-digital-slr/
Showing a gif depicting front tilting would be irrelevant to the point that the focus in the simulation depicts the results of moving the rear standard of a view camera -- that is why I posted the gif of the rear standard moving.


All I’m doing in TiltSim is showing the hinge, ie not the Scheimpflug line.
Yes.  I know.  I have pointed out that fact once or twice myself.

The Scheimplug method is much simpler and easier than the "hinge" to comprehend and utilize.


That is exploiting the J height from sin tilt = f/J and, of course, focus distance.
I am sure that means something, but with Scheimpflug all one really needs to consider is the tilt/swing and the actual focal length.


Ps SelectN is used because of how Desmos works. It does select the 1/3 stop aperture numbers, which are shown on the y axis ;-)
I didn't catch that, due to how the lettering is oriented and because the f-number falls near the line of the "G plane."  It might be good to run that lettering horizontally and position it cleanly in the dead space in the upper left of the graph.


Fully understand all you have said
Okay, but I am not so sure about that.

garry23

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Re: Tilt/Shift Lens Simulator
« Reply #10 on: November 08, 2020, 10:02:25 AM »
@tupp

Quote
Okay, but I am not so sure about that.
.

Good luck with your work and photography.

Cheers and over and out


tupp

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Re: Tilt/Shift Lens Simulator
« Reply #11 on: November 08, 2020, 07:05:37 PM »
Good luck with your work and photography.

Likewise to you!

garry23

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Re: Tilt/Shift Lens Simulator
« Reply #12 on: November 16, 2020, 04:13:22 PM »

garry23

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Re: Tilt/Shift Lens Simulator
« Reply #13 on: November 26, 2020, 12:38:16 PM »
I'm pleased to release TiltSim 2, that is a closer emulation of a 'real' T/S lens: http://photography.grayheron.net/2020/11/tiltsim-2.html

garry23

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garry23

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Re: Tilt/Shift Lens Simulator
« Reply #15 on: Yesterday at 05:10:32 PM »