Need help with tilt and focus calculation

[espelancer]

I am trying to learn calculation based tilt and focus. I have been using GG, but I feel I am getting old and cannot nail it down with a DB, so I am trying to learn calculation based. Here is what I learnt and I need some help.

I have a 60mp Phase one DB and 45mm lens. With those, I calculated the hyper focus distance as approximately 50 feet or 15m. With that the object at distance (beyond 15m) look sharp without tilt.

looking at the snapi app, it tells me that if my lens axis is 2ft above the ground, I should be able to get the ground as well as the distant object sharp with 4.2 degree of tilt without refocus (I used back axis tilt and moved the camera body to keep the back vertical). During the test, the ground does get clearer, but the distant object gets much blurry.

I wonder is my calculation wrong, or my operation?

Basically, I am trying to learn whether with hyper focus, I can forget about focusing when using tilt below 5 degrees.

 

[MGrayson]

If you tilted the back at the base, then you changed the focus (distance from sensor to lens) quite a lot. To get the effect of lens tilt, you'd have to focus further away (move the lens and back closer together).

If you're tilting the back around a central axis, then the numbers should be closer.

How exactly is your camera set up for movements?

 

[dchew]

In my opinion, this highlights the Snapi App's limited usefulness in the field. It tells you the info, but a visual representation of what is going on would be so helpful. It is why I prefer Anders' Lumariver DoF app. Here is a picture from Lumariver with your settings. Note my camera settings are for the IQ4150, so my DoF wedge is a little narrower than yours.


The horizontal red dotted line is the ground, and 2 ft off the ground is a difficult situation even for tilt. It is going to depend on the scene you have. If it is completely flat, like a field of flowers in Kansas, then you should be good. Even though the wedge is narrow, whatever is in the distance will also be at ground level and should be in focus. My guess is what you want in focus in the distance is taller than your DoF wedge. If that is true, you might be better off backing off tilt a little, and dialing in a closer focus setting. Something like this:


In this Lumariver screenshot, the ground should be sharp somewhere around 2.5 feet in front of the camera. This is with a CoC somewhere around 0.023. Your CoC is 0.045, which will help. I would try 3 degrees and a focus distance around 10-15 feet, depending on how close and tall that front subject is. The less tilt you dial in, the wider the wedge. You need a lot of tilt here because the camera is only 2 feet off the ground.

Dave

 

[espelancer]

If you tilted the back at the base, then you changed the focus (distance from sensor to lens) quite a lot. To get the effect of lens tilt, you'd have to focus further away (move the lens and back closer together).

If you're tilting the back around a central axis, then the numbers should be closer.

How exactly is your camera set up for movements?

I tilt around the center axis of the back. I was using Hasselblad Flexbody for testing. It only allows rear center tilt

 

[MGrayson]

I tilt around the center axis of the back. I was using Hasselblad Flexbody for testing. It only allows rear center tilt

Hmm. I leave you in Dave’s expert hands, then. As I’m fond of saying: In theory, there’s no difference between theory and practice. In practice, there is.

BTW, why do you want the back vertical? The geometry is simpler if the lens stays fixed. Or is it that that’s how the apps want it?

 

[espelancer]

In my opinion, this highlights the Snapi App's limited usefulness in the field. It tells you the info, but a visual representation of what is going on would be so helpful. It is why I prefer Anders' Lumariver DoF app. Here is a picture from Lumariver with your settings. Note my camera settings are for the IQ4150, so my DoF wedge is a little narrower than yours.


The horizontal red dotted line is the ground, and 2 ft off the ground is a difficult situation even for tilt. It is going to depend on the scene you have. If it is completely flat, like a field of flowers in Kansas, then you should be good. Even though the wedge is narrow, whatever is in the distance will also be at ground level so should be in focus. My guess is what you want in focus in the distance is taller than your DoF wedge. If that is true, you might be better off backing off tilt a little, and dialing in a closer focus setting. Something like this:
View attachment 200457

In this Lumariver screenshot, the ground should be sharp somewhere around 2.5 feet in front of the camera. This is with a CoC somewhere around 0.023. Your CoC is 0.045, which will help. I would try 3 degrees and a focus distance around 10-15 feet, depending on how close and tall that front subject is. The less tilt you dial in, the wider the wedge. You need a lot of tilt here because the camera is only 2 feet off the ground.

Dave

Thanks. This app is awesome! I just test it out. Though I didn’t figure out how to set focus to 50ft in the tilt view. It seems like I should be able to play with tilt and distance to ground without worrying about focus in most cases.

 

[espelancer]

Hmm. I leave you in Dave’s expert hands, then. As I’m fond of saying: In theory, there’s no difference between theory and practice. In practice, there is.

BTW, why do you want the back vertical? The geometry is simpler if the lens stays fixed. Or is it that that’s how the apps want it?

Good point. I can test without tilting the camera.

 

[dchew]

Thanks. This app is awesome! I just test it out. Though I didn’t figure out how to set focus to 50ft in the tilt view. It seems like I should be able to play with tilt and distance to ground without worrying about focus in most cases.

I don't think you can set focus precisely; the app seems to be designed for that to be an output of the settings. I'm never really sure because the app is so full-featured. It has a longer learning curve. There is a pretty good on-line manual here: Lumariver DoF Manual

You can change the set focus by scrolling the incline column. The other three columns will remain the same and focus will change. If you tap the "focus" box, it will set the far DoF horizontal.

Anders @torger used to hang around here, but its been a few years. There is also a 7 year old (!) thread here: New Depth of Field Calculator

Dave

 

[rdeloe]

For a really simple visual display I still send people to Tim Parkins' tool: http://static.timparkin.co.uk/static/dslr-tilt-shift/

It's not a field calculator but it's handy for visualizing what's happening.

 

[Geoff]

That's excellent, thank you.

One question - it asks for lens length - is this camera-based, i.e. full frame (35mm) equivalent, or independent of camera used?

 

[MGrayson]

That's excellent, thank you.

One question - it asks for lens length - is this camera-based, i.e. full frame (35mm) equivalent, or independent of camera used?

Actual lens focal length. This stuff used to be mostly for LF film. (I mean these days, you can probably get a T/S lens for an iPhone.)

 

[daz7]

I have Lumariver for landscapes and it works great, but I could not find a tool to calculate the tilt angles for close-ups or the macro scale.
Does anyone know of any apps or websites or even better, manual calcualtions to work out the needed tilt angles?

 

[stngoldberg]

I use 1 degree of tilt for every 32 mm of focal length…while focusing about 1/3 into the scene…not scientific by any means, but usually yields really good DOF
Stanley

 

[Smoothjazz]

The one take away I gained by studying the depth of field calculators is that too much tilt actually starts to narrow your depth of field.
It is important to not overdo it- better to titrate up carefully on the tilt amount.
My method is to check focus at the closest and farthest points, switching back and forth as I add more tilt. If you go too far the focus and sharpness will start to decrease.

 

[MGrayson]

I use 1 degree of tilt for every 32 mm of focal length…while focusing about 1/3 into the scene…not scientific by any means, but usually yields really good DOF
Stanley

Good strategy!

Most people think they want the plane of focus on the ground. The one degree per 32mm focal length gets the focus wedge to START at your feet, but focusing closer, as you suggest, gives an upwards sloping wedge, and that will get the biggest part of most landscape in focus. Focusing at infinity, you’d have a horizontal wedge, waste half of it underground, and lose detail in stuff above the centerline of the frame.

Matt