Hyperfocal setting

[D600vince]

Hi,

It'd be great if Remote could set our lens to hyperfocal. If I'd would have been straightforward it'd already be there. So I guess that's not possible because, damn camera manufacturers, you can't set absolute focus distance distance.

But there's hope : can you read the exif of a just taken picture or preview ?
If you can read the exif then continue to read :

- In the exif you've on most camera ApproximateFocusDistance : 335/10 with 335/10= 33.5 m for instance.

I know that this is approximation, but that's better than nothing. And way better than that we're actually able to set on a actual focus range manually.

Now let's imagine that Remote would allow us to "calibrate our lenses". Remote would ask for each focal length of a lens (if that's a zoom lens) that the user do this.
Please focus on minimal focus distance of the lens (can do in af by putting an object to focus on till it's in focus at the minimal lens setting or maybe set directly the minimal focus disantce with focus ring). That's point A Then please focus point B on the moon.

So A would minimal setting, B = infinity (let's say 300 steps).

Now remote would take 300 shots step by steps, and read the corresponding exif ApproximateFocusDistance data and store it, in lens / focal length profile.

So, remote will know the ApproximateFocusDistance of each steps.

Now, when asked to set the camera to hyper focal. Remote will ask : please focus to nearest distance (user would do so in af by putting his hand in front of camera or maybe set directly the minimal focus disantce with focus ring). Click ok when done.

Now remote with go to the nearest step corresponding to the calculated hyper focal looking it up in its' stored calibration table, and would tell the customer it's best to close aperture a bit more.

Added bonus : we would have a "To the moon" setting, so in astrophotography we'l be able to focus on stars without problem

[D600vince]

Unfortunately, My D600 + Tamron 24-70 VC 2.8 reports funky distances (I mean, focusing the same subject will yield 3.98 m at 70 mm, and 2.51 m at 24 mm).

I guess with D nikon lenses, or maybe sigma lenses, or in the canon world it's better

But not all is lost. We can actually measure and record actual distance for the various hyperfocal distances of the lens / diaph.

Since there's only one hyperfocal per aperture and focal length. And since the practical hyperfocal usage are in the 0 -10 range. The user could measure the hyperfocals distance he may use.

For instance for me It'd be 24 mm, at f8 (h = 2.42 m), f11 (h=1.76 m) and f16 (h=1.22 m)

So, once for all, I would put the lens to minimal focus distance, put some object at 2.42 m from the focal plane. and then use the arrow to step up till the object is sharp.

Remote would store that for this lens, at 24 mm, at f8, H=2.42, and is 55 focusing steps away from minimal focus distance.

Now, on the field, when Remote would be asked to set the camera to hyperfocal. Remote would ask the user to put his lens to minimal focus. And then will step up to step 55. Aperture set to f8.

of course remote would display the near limit.
and maybe it could optionnaly with a check box do a secure shot afterwards with aperture set to next step so F9 (with shutter speed lengthened accordingly)

[D600vince]

Or I could evolves in an even more simpler form :

A library of focus distances (steps number) per lens/focal that the user could set.

Remote would ask user :

- Please enter a name
- Please chose the source point - > max focussing distance or minimal focus distance
- Then go to focus bracketing interface and use the arrows to get to the correct distance.
- Memorise.

When user would want to restore a particular focussing distance, for instance "the Stars"

Remote will ask. Please set your lens to max focus distance. Then press go. And then remote would steps BACK according to the stored steps count.

for hyper focal of short lens, where hyper focal is nearer from minimal focus disantce than the maximum one, user would have defined the source point as the min focus distance achievable and hence Remote will ask :

Please set your lens to min focus distance. Then press go. And then remote would steps UP according to the stored steps count.

Saving the source and allowing to be set either from max or min focus distance, will reduce the numberer of steps needed and hence would produce better speed and reliability.

Tipically user will have several settings per lens / focal :

3-4 hyperfocal settings
The stars

[Dan Kozub]

Thanks, I like this idea very much. I think we can implement it as a button for storing focusing position. The program can position to the max or min distance and count steps from there. This should be reliable way to restore predefined position.

I would not rely on EXIF field, as far as I remember its precision is very low. So I would first detect hyper focal distance (manually or automatically) and then save it as an named present ("HF at f8, 70mm")

[D600vince]

Hi Dan,
Glad you like it, thanks

By the way, does helicon remote as any clue about the steps range of a given lens, does he knows all the steps of the lens ? the first, the last

I'm thinking about making lens/focal length steps library in a calibration phase were the advanced user would calibrate the lens for helicon remote (remote will though all the steps to count them).

Then, remote would be in advanced mode for focus stacking were it would go at one position of extreme position, and then go to a particular step number. That way, helicon would know how many steps are ahead and before.

Also, in that calibration phase the user could register actual distance of given steps.

Maybe, the user could have a sphere of specific size, and focus on it. You'd even know the real focal length

[Stas Yatsenko]

Unfortunately, relation between the number of steps and physical movement that can be determined can only be determined experimentally, there's no way to estimate it.

[D600vince]

Do you mean that a step doesn't alway produce focus ring move, does't actually change the focus ?

what is a step actually ?

If it can only be determined experimentally, the calibration i'm talking about makes even more sense

[Stas Yatsenko]

If the lens is already in the end position (0 or infinity), then the lens will simply ignore a command to move focus even further in that direction. Otherwise a step is always performed, of course, but its physical size is unknown and specifc for every lens.
We also have no way of knowing whether the lens have executed focus move or not. There's literally no feedback. So we can't even determine the lenses' focus range automatically.

[orac]

I have never used remote, seeing as I have a windows phone I most likely wont, however I may be able to offer some help for any one with hyper focal, and apeture settings.

As we all know the DoF is affected by appeture, focal length and distance of object from lense (this wont change with moving of the focus ring). Once you know how "deep" you wont your stack to be and how and your DoF you should be able to dictate the number of shots that need to be taken

CoC: Circle of confusion, this is normally 0.019948 for APS/APS-C sensors and 0.02501 for full frame
Distance: distance of subject from lense
Focal: focal length of lense (take data from test shot)

all distances in millimeters

Hyperfocal = (FocalLength * FocalLength) / (Apeture * CoC)

Near Point = (HyperFocal * distance) / (HyperFocal + (Distance - Focal))

FarPoint = (HyperFocal * Distance) / (HyperFocal - (Distance - Focal))

Total DoF = FarPoint - NearPoint

Re-arranged for calulating apeture:

Hyperfocal = (Nearpoint * (Distance - FocalLength)) / (Distance - NearPoint)

Hyperfocal = (Farpoint * (FocalLength - Distance)) / (Distance - FarPoint)

(take an average of to hyper focals, ie somewhere in the middle)

Apeture = (FocalLenght ^2) / (CoC * HyperFocal)

You will need a ruler or alikes to measure the distance from lense to object, also dont forget to add in some over lap of each imagem this i would imagine will cause out of focus parts to be proccessed into the final image.

Stas, would it be possible to add a calculator to do these claculations into later version of the software, I currently use a spread sheet along side my macro rail (currently need a PC terminal to feed info back to user) which is fine at home, but a little tricky in the feild I should imagine

[D600vince]

Thanks Orac,

Remote already has an hyperfocal calculator.

But the problem is not the calculation, it's to report the computed distance to the lens. The only reliable way I think is to use laser measure tool with pointer and focus to the point, if you have good practical trick to do this you're welcome to share

As far as the calculation, there's many many app on iOS / Android that do that computation. I'm shure there's also on windows phone or the'll come soon !

[orac]

As it so happens I ill be Working on one soon. And yes there are HF calculators for windows but they dont seem very accureate, most only going to the nearest mm, while my current rail is accurate to 0.15mm and the rail I am currently designing should be some where in the region of 0.00125mm, then later with soom further electronic development will be close to 0.0003125mm.

How close to the lense are you? should actually be fairly simple with some basic electronics and a white card

[D600vince]

I thought we were talking about hyper focal.
Hyperfocal is minimal focus distance from which everything is sharp from it to infinity.
It's used for single shots, not stacking, meters away usually.

What you seem to talk about is depth of field between each steps. So we're not talking about the same thing at all.

[D600vince]

Moreover,

I didn't check your algorithm, but I remember that for macro work (which you seem to do because you use a rail), the equations are not the same as those to compute the hyper focal and such. That may explain why you find the already available software not precise enough.

That's because they're not meant for macro. The macro equation are not the one you posted.


Here's an online Macro DOF calculator
http://www.tirpor.com/macro/macro_DOF.htm

[orac]

Hyper focal is required for calculating DoF. The reason for it not being a accurate enough is the apps only run to a whole millimeter while most macro DoF is less than 1mm.

heyper focal =(focallength^2)/(aperture*CoC)

Focal length is in mm, so result is in mm, resultant sums should be in mm. So in the later sums can result in less then 1mm due to CoC being less than 1.

[D600vince]

Do some research, Macro DOF is not driven by same equations, that's the way it is.