Difficulty focusing with rear tilt

[coops]

Took out my fairly new and first 4x5 camera and wanted to take a shot slightly distorting the foreground. Once the camera was level and everything in its neutral position, I tilted the film plane back until the foreground looked good and sharp. I had a 150 mm lens which was opened up all the way.
I then tilted the lens slightly forward until the background was sharp, but of course the foreground was now not sharp. And so it went on, and on and on. Any adjustment to one put out the other. I was also playing with the focusing knob to no avail.
I stopped down to f/22 which helped, but still could not get both as sharp as I think is possible. I could not see well at f/32 even with a loupe.
Do you guys have a regimen you follow to get sharpness using rear titls? Any advice is appreciated, thanks.

[Bill_1856]

You tilted the lens the wrong way.

[Adam Kavalunas]

First, I almost always focus with my lens wide open. Focus first on the most distant part of the scene that you want to be in focus, this usually means focusing the very bottom of the screen. Then tilt backwards until the foreground comes into focus. This will of course through the rear part of the scene out of focus. Then use the focus knob to once again re-focus the background of the scene. As expected, this will usually through the foreground out of focus again, but not by as much as before. Once again, tilt the rear standand backwards just enough to regain focus in your foreground. Just keep doing this, usually 2 complete run through's is enough and the scene will be all in focus. Now just stop down to get the middle ground into focus and you're ready to shoot!

Adam Kavalunas
www.plateauvisions.com

[Adam Kavalunas]

I forgot to mention, my focus method never mentions touching the front standard. To my recolection, I've never used front tilt or swing, just rise and fall. I prefer to keep my image circle as centered as possible, and therefore only use tilts and swings on the rear standard.

[Nathan Potter]

First of all are you sure that you didn't tilt the lens beyond its coverage range. I assume you tilted the front standard so that the top of the board is closest to the film plane placing the distant scene elements in focus at the bottom of the film plane and the near scene elements in focus at the top of the film plane. That alone should suffice to produce a wholly in focus plane from near to far using the focusing and tilt function sequentially while keeping the back standard vertical. But remember only the Scheimpflug plane will be in perfect focus- any objects projecting out of that plane in a vertical direction will be out of focus at maximum aperture. Stop the lens down to obtain a sharper focus on the out of plane objects. As mentioned above you could tilt only the back plane to achieve the Scheimpflug condition and that has the advantage that the optical axis remains in the center of the film, eliminating the coverage issue.

I can't quite figure out why you would want to tilt both front and rear standard unless you are trying for some additional perspective correction.

Nate Potter, Austin TX.

[coops]

I forgot to mention, my focus method never mentions touching the front standard. .

Thanks very much. Don't know why I thought I had to mess with the front standard in the first place, Thats why I ask you guys. Thanks again.

[coops]

Now just stop down to get the middle ground into focus and you're ready to shoot!

Adam Kavalunas
www.plateauvisions.com

So I should expect to get the near and far into focus, not the middle? Makes sense now.

[Brian Ellis]

Go to the home page for this site. You'll see a heading called "Taking the Picture." Under that heading you'll see two articles by Tuan, one called something like "Focusing the View Camera," the other something like "Determining the Optimum Aperture." Read them and then use them. They'll make your large format life much more enjoyable and if you apply them properly you'll never have an out of focus photograph or a photograph that lacks the depth of field needed to make the photograph you wanted to make.

[Rakesh Malik]

So I should expect to get the near and far into focus, not the middle? Makes sense now.

The middle ground will be in focus if it's in the same plane as the foreground and background. If not, you'll have to bring it into focus by increasing depth of field.

And also don't forget that the same procedure works from side to side as well.

[coops]

Thanks for all the responses. I got to shoot today using the advice posted, and my negs look very sharp. I was suprised at how little rear tilt was needed to achieve good focus.

[Nana Sousa Dias]

Thanks for all the responses. I got to shoot today using the advice posted, and my negs look very sharp. I was suprised at how little rear tilt was needed to achieve good focus.


If you use a very wide angle lens like the 47mm, in most cases you move the back a only 1 or 2 milimeters, unless you have some element at about 20cm of the lens and want everything on focus, from there, to infinity. In that case, probably you will move the back about 1cm!!!!

I think you may be influenced by the commercial advertising photos of several large format camera brands, in magazines, wich show their cameras completely twisted, in some positions one will never need, some of those movements don't make any sense but, that can sell a camera and it's good to know that a particular camera as a good range of movements, even if we are not gonna need to use the extreme movements. I have had untill now 5 4x5 cameras and never used the extreme movement of any of them, except front rise.

[Leonard Evens]

Let me describe the method I use.

First note that in most cases, you are not trying to just focus on one plane. You want to choose a region in space in which everything will be in focus. This region has the shape of a wedge centered on a line somewhere in front of the camera (for a back tilt) called the hinge line and bounded above and below by two planes which pass through that line. The position of the exact plane of focus is approximately halfway between the upper and lower planes. The angle between the upper and lower planes is determined by the f-stop at the taking aperture. After you pick your back tilt and aperture, the amount in focus transverse to the exact plane of focus will be narrow in the foreground and increase as you move into the background. It generally won't be possible to get a lot in focus in the foreground this way.

So the first thing you should do is to determine the upper and lower points you want in focus and then choose a plane about halfway in between them which you want to be exactly in focus. In principle, using back tilt, you should be able to keep some part of this exact plane in focus as you tilt. Choose two other points, near and far in that plane. As you tilt, you should find that these points then come into focus.

If that doesn't work, then you have to use the iterative process described by others above.
As above, fix a near point and far point in the desired exact plane of focus. As others noted, you do this part with the lens wide open. Here is how I describe the iterative process. Choose some tilt as a first guess. Something like 5 degrees might be a good choice, but it is not crucial what you choose. Then focus on the far point, note the position of the rail on the standard and refocus on the near point. If in doing so, you need to move the standards further apart, then increase the tilt. If instead you need to move the standards closer together, decrease the tilt. Each time increase ofr decrease less than you did the previous time. After a few iterations of this procedure, both near point and far point should be in focus.

Next, you need to choose the taking aperture so that the upper and lower points are in focus. There are two ways to go about doing this. First, just stop down and observe what happens on the gg. Use a loupe. When both upper and lower points are in focus, then that aperture should work. You may also in this process decide to adjust the focus, which will move the entire wedge.

Unfortunately, if you have to stop down much past f/16, you won't be able to see what is in focus to judge because the image will be too dim. If so you can use the following alternate procedure. Focus first on the upper point, note the position on the rail of the standard and then focus on the lower point and do the same. Measure the distance in mm between those poin ts on the rail. That is called the focus spread. Then use the focus spread to determine the f-stop. One simple rule is to multiply the focus spread by 10 and then divide the result by 2. So if the focus spread is 4 mm, you would get 4 x 10/2 = 40/2 = 20. Then close down further to the nearest f-stop (or fraction of an f-stop0 So in the example you would use f/22.

But this method for determining the f-number ignores diffraction. If you want to include diffraction, you can use the method described in Tuan's article based on a method of Paul Hansma. Or you can just stop down an additional stop or so.