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Author Topic: A new tool for the production of high quality output  (Read 9004 times)
Hening Bettermann
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« Reply #40 on: September 13, 2013, 03:56:39 PM »
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Hi Bart,

thank you for your reply. Your tools are indeed a great help, and so are your software recommendations, which are highly appreciated.

As for the print service: I don't use jpegs other than for web display. I could not afford/justify the purchase of a large format printer, so I searched for the cheapest german print service that does tifs, and I am overly satisfied with digitaloriginal.de. I have the most excellent communication with the owner, Mr. Hamacher. His combined upsampling and output sharpening was better than what I could achieve using PS softproof and Qimage sharpening. (no affiliation with him).

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Proceeding to the Camera-lens Settings and Focus Stacking panes rises some questions:
Example: f=85mm, f/8, I leave the pupil factor at 1, because I am too lazy to determine it; I want the max DOF, so I set Focus Distance to the hyperfocal distance=55.53 m.
In landscape, the whole frame is the "object". The tool shows width=23.48m, height=15.66m. Which significance has this? Does it have any influence on the subsequent calculations?

Then, I copy the settings to Focus Stacking and assume that I want DOF from 5 m to infinity.
What is the Goal Distance Range? (In the example, it is given as 9.999e+ - I have a vague feeling this means "infinity".) - What is the Search: Front-Rear-Aperture? Regardless which of the radio buttons I click, nothing seems to change.

3.5 is called the MAX number of images, 6 in the example. These 6 slices are without any overlap. So shouldn't 3.5 be named MINIMUM number of images? In real life, you want overlap, Helicon recommends it, so you will need more slices. Or ...?

Kind regards - Hening.

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BartvanderWolf
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« Reply #41 on: September 13, 2013, 05:50:39 PM »
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Proceeding to the Camera-lens Settings and Focus Stacking panes rises some questions:
Example: f=85mm, f/8, I leave the pupil factor at 1, because I am too lazy to determine it; I want the max DOF, so I set Focus Distance to the hyperfocal distance=55.53 m.
In landscape, the whole frame is the "object". The tool shows width=23.48m, height=15.66m. Which significance has this? Does it have any influence on the subsequent calculations?

Hi Hening,

The object/subject dimensions are the scene 'frame' dimensions in the focus plane. This is used for determining if a subject that is focused on, will fit in the frame. It's mostly used to fit e.g. a building facade  with known dimensions, or a person of known height, or a car or a truck of known length, a painting of known dimensions, etc., within the frame. You get the idea what it can be used for. A landscape is not typically measured that way. It is directly related to the sensor size and magnification factor, and the latter is directly related to the focal length and focus distance. So in that sense it's related to all other parameters and vice versa.

Quote
Then, I copy the settings to Focus Stacking and assume that I want DOF from 5 m to infinity.
What is the Goal Distance Range? (In the example, it is given as 9.999e+ - I have a vague feeling this means "infinity".)

The goal distance range is the depth you want the focus stack to have, the goal you want to achieve by stacking, in case you have a specific range in mind (e.g. an object or subject that needs to be sharp from a given distance to another distance). Since you've focused on the hyperfocal distance, a single slice will already span the distance from half the hyperfocal distance to infinity.

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- What is the Search: Front-Rear-Aperture? Regardless which of the radio buttons I click, nothing seems to change.

When you change the total range or depth of the zone you want to have in focus, you need to instruct the program where to look for an expansion of the range. Upon changing the total range, you can have it expand that range by searching for a new front distance (and keeping the rear unchanged), or for a new rear distance (and keeping the front unchanged), or for a new aperture that allows to span the range from front to rear (which may fail when the range is larger than can be achieved by the smallest aperture you can select, and will be heavily diffracted).

Quote
3.5 is called the MAX number of images, 6 in the example. These 6 slices are without any overlap. So shouldn't 3.5 be named MINIMUM number of images? In real life, you want overlap, Helicon recommends it, so you will need more slices. Or ...?

The number of slices needed is the automatic result of focal length, aperture, COC, and Total range to cover. You can limit that number of images by entering a lower maximum. Increasing has no use, because the front to rear distance will already be covered by fewer slices. Setting a lower maximum can be useful for limiting the number of slices to a specific number, e.g. the length of a focus rail in macro where each image is shot with the same magnification factor and thus slice depth. Especially when selecting a relatively close front distance, that can result in an impractically huge number of slices which will take a long time to calculate, it can be useful to then set a limit. Other than that, it is not that often used for input, but rather for reporting the total number of slices.

There is no real need to overlap the slice boundaries because you've already selected a resolution on sensor that is 'perfectly' sharp (according to COC limitations) in the end result, based on the prior input parameters. In fact the sharpness between the DOF range boundaries will still increase towards the plane of optimal focus in between those boundaries (unless limited by sensel pitch), but you won't be able to resolve that in the output by eye. There will be no visible gaps in sharpness between the slices, which should indeed be avoided, hence the recommendation by HeliconSoft.

Cheers,
Bart
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Hening Bettermann
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« Reply #42 on: September 14, 2013, 08:43:05 AM »
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Hi Bart,
thank you for your extensive answer!
Kind regards - Hening.
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lelouarn
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« Reply #43 on: November 20, 2013, 07:07:37 AM »
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This is a really interesting tool, and it would be interesting to have an app to do that in the field (although I guess after a while, one will remember the values by heart).

What I would like to do, is focus a tech-cam by the numbers (i.e basically hyperfocal distance, then change aperture if there is a really nice foreground - or something like that).

Now I thought, it's easy, I just take the CoC value given for my desired printing size from the web-tool, and plug it into a "conventional" DoF calculator. I happen to have TrueDoF-Pro on my iPhone. With my settings, (IQ160, Landscape, 32mm lens, f/8, 0.5m viewing distance, I get a hyperfocal of 21.04m), I get a CoC value of 6um (~1x pixel size, by the way, it seems my choices are picky, since usually one selects ~1.4 - 2 x pixel size).

Well on the TrueDoF-Pro, to replicate roughly the Hyperfocal from the web-page, I need to use a CoC of 12um ! That's strange. The other values are also "similar", TrueDoF-Pro yields Front distance of 11.6m (web-tool 10.59).

TrueDoF-Pro says it takes into account diffraction, so that's a possible source of difference. If I set the f number to 11 in TrueDoF-Pro, I get infinity on both front and rear focus, which could indicate that diffraction smoothes everything out. But maybe I'm trying to debug TrueDoF-Pro or am doing something wrong with it :-)

What do you think ? Is it possible that other assumptions would change things by so much ?
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BartvanderWolf
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« Reply #44 on: November 21, 2013, 06:36:21 AM »
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TrueDoF-Pro says it takes into account diffraction, so that's a possible source of difference.

Hi,

I think it is. They seem to adjust the COC by a certain amount depending on the amount of diffraction.

In my tool, I only report the reduced MTF that is caused by diffraction (but do not increase the COC), until diffraction results in a zero MTF (beyond which my tool does increase COC). I made that (reporting instead of adjusting) trade-off, because system MTF is also dependent on lens MTF (which is unknown until measured for a particular lens), and unknown AA-filter, an unknown sensel aperture (micro-lens, transfer gates, etc.), and obviously subject contrast is variable and diffraction differs by wavelength.

So I figured that, given so many variables, it only makes sense to not assume an effect on COC (but there will be additional signal deterioration), until it kills all signal. That deterioration knows no hard boundary (except for MTF=0), so one can use the results of my tool as guidance for planning, but absolute performance depends on some additional factors. Besides, deconvolution sharpening can restore some of the visual deterioration, as long as the system MTF is above zero.

Quote
What do you think ? Is it possible that other assumptions would change things by so much ?

I'd have to study how their weighting of those variables is assumed to affect the actual COC assumption before I can comment on that. I do get a feeling that they try to use the COC to incorporate other effects that affect the impression of sharpness. I do not know if they made sensible assumptions, but it seems difficult to translate reduced contrast to absolute cut-offs.

Cheers,
Bart
« Last Edit: November 22, 2013, 04:54:35 AM by BartvanderWolf » Logged
lelouarn
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« Reply #45 on: November 21, 2013, 10:02:09 AM »
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Interesting...
I guess one should actually measure the MTF of the whole system, Lens -> Camera -> Processing -> Printing. But that is a can of worms probably nobody is willing to open :-)
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BartvanderWolf
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« Reply #46 on: November 22, 2013, 04:59:34 AM »
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Interesting...
I guess one should actually measure the MTF of the whole system, Lens -> Camera -> Processing -> Printing. But that is a can of worms probably nobody is willing to open :-)

Hi,

Well, in a sense the can is open for those who want to, except for the physical printing part which comes with it's own set of challenges.

Cheers,
Bart
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AlfSollund
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« Reply #47 on: November 24, 2013, 05:19:54 AM »
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Thnaks a lot for sharing this excellent tool. I really like this no-nonsense interface.

So, a question/wish; Would it be possible to let the user adjust the 1.3 px parameters in case of cropped images, i.e. instead "the camera's sensor array" to become the "the used part of camera's sensor array" (as I do all the time)?

Btw: Imo you could prioritize the functionality and "engine" before supporting strange non-SI choices (sorry to the US residents living in America, its really time you catch up with the modern world in term of units  Wink Cheesy ).

Again, thanks a lot.
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BartvanderWolf
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« Reply #48 on: November 24, 2013, 07:00:09 AM »
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Thnaks a lot for sharing this excellent tool. I really like this no-nonsense interface.

So, a question/wish; Would it be possible to let the user adjust the 1.3 px parameters in case of cropped images, i.e. instead "the camera's sensor array" to become the "the used part of camera's sensor array" (as I do all the time)?

Hi Alf,

Currently the only way to do that is by scaling both the sensor (Width and Height) and the pixel dimensions by the same amount, causing the sensel pitch to remain the same. That would require to calculate and change 4 values, doable because you only need to do it once for the session, but not convenient with repeated use.

I could add a 'Scale factor'. I'd prefer to avoid the use of the term 'Crop factor' because that can also add confusion about focal lengths. I'll have to think a bit about this, because it will impact several calculations, and I don't want to break things.

I'm also considering to add some panorama stitching functionality, which should use the full sensor size, so I cannot just change the initially entered dimensions, but have to only add the scale factor(s) to selected/relevant calculations.

I'll see what I can do, it'll take a bit of time.

Cheers,
Bart
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AlfSollund
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« Reply #49 on: November 24, 2013, 09:29:04 AM »
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Hi Alf,

Currently the only way to do that is by scaling both the sensor (Width and Height) and the pixel dimensions by the same amount, causing the sensel pitch to remain the same. That would require to calculate and change 4 values, doable because you only need to do it once for the session, but not convenient with repeated use.

I could add a 'Scale factor'. I'd prefer to avoid the use of the term 'Crop factor' because that can also add confusion about focal lengths. I'll have to think a bit about this, because it will impact several calculations, and I don't want to break things.

I'm also considering to add some panorama stitching functionality, which should use the full sensor size, so I cannot just change the initially entered dimensions, but have to only add the scale factor(s) to selected/relevant calculations.

I'll see what I can do, it'll take a bit of time.

Cheers,
Bart

Thanks again,

Yes, I assume I can approximate by scaling the output values in 1.4 by my scale factor (crop sensor factor).

About wording: A a 'Scale factor' would be different up and downwards seen from me as output from Lightroom. If I scale downwards by cropping I keep the original quality (per pixel). If I scale upwards by "Enlarge" in LR export I change the quality by letting LR extrapolate.
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- If your're not telling a story with photo you're only adding noise -
http://alfsollund.com/
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