Talking Technical on Tech Cameras

[f8orbust]

Jae, that all makes sense - not sure what happened with my thinking - got caught in at least two minds + general brain fade I suspect.

Just a couple of points. 1) I wasn't trying to depict refraction - now that would be a step too far for my brain - simply the distance from the 'centre' of the lens to the edges of the sensor. 2) As long as the 'centre' of the lens is in front of the axis of rotation, then focal length isn't related to focus-shift, since the distance from the axis of tilt to the sensor plane is the same for whatever lens is stuck on the T/S adapter, and however much it is tilted. However this is only true of lenses in front of the axis of tilt, once the 'centre' of a lens is behind it (such as with some retrofocus lenses or lenses on recessed boards) then the value of 'actual distance' (and thus the degree of 'focus shift') will vary according to focal length. 3) Longer focal length lenses tend to require more tilt on certain occasions (e.g. landscape: foreground to background in focus) which means the 'actual distance' in your diagram tends to be greater with longer focal length lenses and thus the effect is greater, both of 'focus shift' and the appearance of the subject on the sensor, due to the divergence of the values e and f on my amended diagram.

Jim

 

[Jae_Moon]

It is not a simple task to do Tilt/Swing correctly but it is not a Brain Surgery either. Two previous posts by me and f8orbust should not scare anyone, they are only theoretical discussions between two 'gear heads'.

The 'focus shift' that we discussed does not affect when you do the focusing by visual confirmation; GG, built-in display or tethered (and it does not exists in a real world situation since you do not know the 'calculated focus distance'). It applies only if you calculate the required focus distance. But even if you do use the calculation, the fix is just adding an equation to correct, therefore, there is no focus shift in any Tech Camera with any focal length using mathematical formulae.

It is true that a longer lens requires bigger tilt than a short lens under the same settings (thus increasing the focus shift in calculation), but it is also true that a longer lens is much more forgiving to the focus shift since the longer lens has longer focus adjustment range. For example, the focal length changes 0.15 mm for SK90 and 0.02 mm for SK35 when you move the object distance from 2.3 m to 2.4 m.

The conclusion? Don't let these theoretical talks scare you, find a way that suits you and keep working on it until you are happy with your results.

It is a simple 'Cost/Benefit' optimization; to obtain the best results (to your eyes) with the minimum efforts (in your part) to achieve it.


Jae M

 

[photomgraphy]

alpha = arcsin (f/J), where alpha is lens tilt angle, f is lens focal length in mm, and J is the vertical distance between lens axis and your Plane of Sharp Focus in mm.
Fd = J / sin(alpha), where Fd is the calculated focus distance in mm.

Jae M

- SK35 at 8.0 aperture and CoC setting of 3 pp of P45 (0.02mm)
- Ground to be the plane of Sharp Focus

- If Camera Height is 1 meter, Tilt angle is 2.1, Focus distance is 29.6 meter and HFD is 8.1 meter
- If Camera Height is 1.5 meter, Tilt angle is 1.4, Focus distance is 68.8 meter and HFD is 8.1 meter

Jae M

jae, i'm a little confused about the formulars:

if i try to calculate the above settings the result is:

arcsin(35/1000)= 0,035
these are radiens right? if i want degrees - i'll have to multiply with 180/pi

and
1000/sin(2,1)= 1158,5 there i should have inserted in the radians not degrees
am i right?

how about the formular of HFD and DOF?

thanks for the interesting discussion :thumbup:

 

[f8orbust]

Tilt = arcsin (35/1000) = arcsin (0.035) = 2.01 degrees
Focus Distance = 1000 / sin (2.01) = 28.5m

All distances in mm (unless otherwise stated) and angles in degrees.

 

[photomgraphy]

ok, but when i insert the formular in excel =arcsin(0,035) the result is 0,03500175???? :wtf:
obviously that's not correct ...
what does this program do? :loco:
when i multiply with (180/3,14) i get: 2

what did i wrong?

 

[photomgraphy]

although i don't understand why excel calculates in radiant - it does.
so i have to convert to degree.
formular: =GRAD(ARCSIN(F/J)) --- german version: grad=degree ;-)

 

[Jae_Moon]

jae, i'm a little confused about the formulars:

if i try to calculate the above settings the result is:

arcsin(35/1000)= 0,035
these are radiens right? if i want degrees - i'll have to multiply with 180/pi

and
1000/sin(2,1)= 1158,5 there i should have inserted in the radians not degrees
am i right?

how about the formular of HFD and DOF?

thanks for the interesting discussion :thumbup:

Without getting into a Math tutoring :

There are different units in math and physics; Deg C or Deg F, meter or yard, etc. In most higher level math, the unit of measuring angular degree is 'radian' not 'degree'.
A circle is 360 degree or 2 x Pi radian, where Pi is 3.1415.....
In order to use Excel or Numbers, you have to convert your 'degree' into 'radian' by RADIAN (# of degree) and convert 'radian' into 'degree' by DEGREE (# of radian).

Harold Merklinger published two books (The Ins and OUTs of Focus, Focusing the View Camera) and you can download PDF version from online site. Just google 'Harold Merklinger' and you will see it. You will learn all about DOF, HFD, Tilt, etc.


Jae Moon

 

[photomgraphy]

thanks got it, now lets see if my english is good enough to understand it ;-)

 

[Jae_Moon]

Tech Camera and Digital Back


Since my purchase of P45 in the spring of 2006 Phase One have introduced three upgrades; P+ series, IQ1xx and IQ2xx. I have faced the temptations to upgrade to newer model with each upgrade and went thru my own 'justification/rationalization' processes.

First of all, I am not a professional, doing OK financially and have a reasonably understanding wife. Therefore, the decision to upgrade or not is wholly depends on my ability of convincing myself if an upgrade is justified.

I used P45 with H2 and AS F-Metric for five years until I replace both with AS RM camera in 2011. P45 worked well with H2 since H2 had an excellent auto-focus and a great optical viewfinder (I was using the display of P45 mainly for checking histogram). I also wanted to use my F-Metric with P45 since I had four great Schneider lenses (35, 47, 90, 210) but it didn't worked out for me (difficulty of focusing with GG).

It was an easy decision not to upgrade to P+ series since I had 'Skip One Generation' policy and I believed 39 MPx were more than enough with my 24" printer (so no need to look at P65+).

With IQ1xx, it took a longer debate internally since it had a strong selling point, a 'better display.' 'Better focusing and composing' with the new display would mean that I could use my F-Metric more with better results. About the same time period, I started to notice Tech Camera (ALPA in the beginning) as a possible replacement to my F-Metric since I liked the idea of focusing with accurate object distance measurement. But it still lacked a 'view finder' the new IQ1xx provides. Then, I read the review of AS RM camera in Luminous Landscape (both reviewers didn't care much) and noticed the feature called 'Indexed Focusing,' which turn a light-bulb in my head on. After that, my evaluation was focused on two approaches of accurate focusing; with 'focus mask' in an IQ1xx versus 'indexed focus' with laser rangefinder. In the end, I decided to go with AS Rm3di and to skip another generation of upgrade.

Now, I am facing with another temptation, IQ2xx. It is reasonably easy for me to assume that the Image processing technologies have improved significantly during past seven years, and I can justify to upgrade with that assumption alone. The key selling point of IQ2xx, a direct wi-fi connection to an iOS device, is a nice feature but I am not sure the premium is worth 2.1 pounds saving in weight from Macbook Pro 13 Retina (or 1.5 pound from Macbook Air 13) against carrying an iPad.

So now I am tossing between getting an used IQ160 (hoping many would sell their 160s to get 260s) and skipping another generation.

Jae Moon

 

[AndyPtak]

This is one of the most useful threads I have read in a long time.

But the math required is beyond an old geezer like me. Long time since I went to school and even then I flunked math.

So publish and sell an aplication my friend, I'll be the first in line. Now, if only I could find my glasses.

 

[Jae_Moon]

Distance Measurement with Laser RangeFinder


I have two Laser Rangefinders to measure the object distances; Leica Disto 5 and Leupold RX1000. Each has its own strengths for a landscape photographer like me who focuses a tech camera based on the distance measurement.

Leica Disto 5:

It uses both a 'red' laser point and 'digital pointfinder' which is a built-in video camera with up to 4x zoom. The 'red dot' laser pointer is difficult to see and is almost useless in outdoor application. The 'digital pointfinder' is easy to use, as long as it is on a tripod, and very accurate. A simple distance measurement can be done in 'digital pointfinder' mode in two-steps; aim an object with crosshair in LED viewfinder then press Red 'Distance' button. To measure x and y distance of an object for Tilt/Swing, you have to first locate the object with LED viewfinder then use proper 'function key' sequences.

The specification claims the distance range up to 100 meters but I haven't been successful to measure farther than 40 - 45 meters in actual field application. I did measure an object (aluminum Street sign) that is 65 meters away but the range is more limited with 'natural objects' such as tree trunks or rocks. It claims 1.5 mm accuracy up to the distance of 30 meters (I haven't verified it ).

Leupold RX1000:

It is very small, a monocular with 6x optical viewfinder and use 'pulse of infra red' to measure the distance. It is designed for handheld use and does not have a tripod mounting screw hole.
I needed a rangefinder which can measure the distance between 50 and 100 meters accurately (of tree trunks and rocks) and Leupold does very well. Leupold has a model with a built-in Inclinometer (to measure the angle from the horizon) but I chose the one without it.

I made several measurement soon after I got it while walking a nearby nature/bike trail. The trail has 'half mile' markers (805 meters) and is winding, so I had to make 5 - 8 measurement of varying distances while covering a 'half-mile' increments. I picked non-reflecting objects; tree, power poles, bench, rocks, etc., from 40 meters to 350 meters distance, and added up for each 'half-mile' marker to see the combined accuracy. I was handholding it and made two readings for each object and keep the average. The overall accuracy of my measurement was approximately 5% higher, never lower. I concluded that it was an operator's error, not able to hold it steady and got the reading for the tree behind.

The specification claims the distance range up to 640 meters of non-reflecting surface (such as tree) with 2.5% accuracy the distance beyond 110 meters. The minimum distance is 5 meters.

Jae Moon

 

[awolf]

Check this out (repost form Arca Rm3di) :

https://itunes.apple.com/us/app/tilt...529611767?mt=8

 

[torger]

Anyone that has a tip for a small compact optical rangefinder (not laser)? It does not need to be that accurate, I'd just like to have something that could help me figure out if the distance is about 30, 50, 80 or 130 meters...

 

[stephengilbert]

Leitz and Fotoman both made small optical rangefinders. I used to have both, but sold my Fotoman to some guy in Carmel.

You could check eBay.

 

[Jae_Moon]

Check this out (repost form Arca Rm3di) :

https://itunes.apple.com/us/app/tilt...529611767?mt=8

Let us know how it works and how you like it.

Jae Moon

 

[awolf]

I was hoping some of you "pros" can tell me

 

[torger]

Leitz and Fotoman both made small optical rangefinders. I used to have both, but sold my Fotoman to some guy in Carmel.

You could check eBay.

Thanks for the tips. The Leitz fokos rangefinder looks really cute, quite expensive though. I have an all-mechanical camera, mechanical watch for longer exposures, so of course I want a retro-looking mechanical rangefinder to use with my DoF tables . Unfortunately the prices on it seems quite high...

Tried the Disto D5 and it's nice, but it's a heavy thing with batteries with overkill precision. As a ground glass user the D5 precision is not necessary. The rangefinder would be used to find out which aperture to use for sufficient DoF, or if it's useful to tilt, but setting the focus is done by looking at the ground glass with loupe.

I do nowadays carry a small key-ring laser pointer though, which can be used in very poor light conditions to get a spot to focus at.

 

[Jae_Moon]

Tried the Disto D5 and it's nice, but it's a heavy thing with batteries with overkill precision. As a ground glass user the D5 precision is not necessary. The rangefinder would be used to find out which aperture to use for sufficient DoF, or if it's useful to tilt, but setting the focus is done by looking at the ground glass with loupe.

Ander:

You may look into Leupold series if you don't mind its 'non-retro mechanical', but it comes in hunter' camouflage . It is very small, half the size of cigarette pack (a bit thicker). It's shortcoming, as stated in my previous post, the minimum distance range is 5 meters or so. However, I found it much easier to use than Disto for general distance measurement. Target marker and distance measurement are visible in viewfinder such that you can locate, aim and measure the distance in one motion.

Jae Moon

 

[Shashin]

Thanks for the tips. The Leitz fokos rangefinder looks really cute, quite expensive though. I have an all-mechanical camera, mechanical watch for longer exposures, so of course I want a retro-looking mechanical rangefinder to use with my DoF tables . Unfortunately the prices on it seems quite high...

The Ansco DeJur is is a really nice rangefinder modeled after the Leica design--this is the one I used with a Horseman SW612 and I still have. Waterman and Voightlander made good rangefinders too. Waterman has a close focus model. The Kodak rangefinders, while sophisticated, can yellow and darken with age.

 

[Malaba]

Hello everyone on this forum!
I just registered on get dpi in order to let you know that this a great thread.
Can't wait for this app to be available.

I'd also like to point you to this app (maybe you already use it) called Snapi, made by Guillaume Sébire. The app works well for calculating tilt angle and focus distance to get a horizontal or slanted plane of sharpness, even with a tilted camera.