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View Full Version : Reference point idea? On a Tachihara



Wanderon
3-Dec-2006, 11:18
I saw here a thread or a site that showed a way to put a arrow on the side of your camera to give you reference points with your distance measureing on the frame of this camera, to give more accurate focus ... is there anyone here that has or knows where this info can be found
Thanks
Lynn

Brian Ellis
3-Dec-2006, 23:50
Are you talking about using a mm ruler and a pointer for purposes of determining the mid-point between near and far fto determine where to position the lens for proper focus? If so I did that on a Tachihara. I cut out a fabric mm ruler purchased at Home Depot or somewhere like that, used double sided Scoth tape to tape it over the cm ruler that's already on a Tachihara (too bad the ruler Tachihara provides is in cms, mms would have been perfect for this purpose), then cut out a couple little carboard pointers and taped them along the part of the camera above the ruler that moves as the lens is moved, one towards the front and one towards the back. It worked fine for quite a few years. I've done the same thing on every camera I've owned, including a couple Deardorffs and a Kodak 2D. Linhof Technikas are great for this, they already have the pointer and you can tape a mm ruler inside the distance scale holder.

Wanderon
4-Dec-2006, 05:16
Yes, that's what I was looking for but there is a actual thread or site that shows where there to be placed ... I've seen it just can't find it again
Thanks
Lynn

Leonard Evens
4-Dec-2006, 06:12
You can obtain better accuracy, particularly for relatively small focus spread along the bed, if you put a scale on the focusing knob. I don't know how the Tachihara works, but usually the focusing knob is geared down to allow for fine control of the focusing position. It is simply a matter of determining the ratio of a displaement on the circumference of the knob to the corresponding displacement on the bed. You can look at www.math.northwestern.edu/~len/photos/pages/dof_essay.pdf to see how I did this for my Toho FC-45X. Using that, I can focus down to an accuracy of a couple of tenths of a mm.

Ed Pierce
6-Dec-2006, 10:22
In the meantime you can do what I have with my Zone VI...carry a metric pocket tape and measure the distance from the film plane to the lensboard.
This always works no matter which standards(s) I use to focus. The drawback is it's one more thing to lug around and possibly drop in the river.

Alan Davenport
6-Dec-2006, 13:02
Seems like unneeded effort from my perspective. I focus my Tachihara by using a 4X loupe to examine the image on the groundglass. Seems to be pretty accurate, too. How does measuring on the bed improve on that?

Chauncey Walden
6-Dec-2006, 13:07
Alan, check this out: http://www-unix.oit.umass.edu/~rbhome/focussummary.pdf

David Karp
6-Dec-2006, 14:41
Seems like unneeded effort from my perspective. I focus my Tachihara by using a 4X loupe to examine the image on the groundglass. Seems to be pretty accurate, too. How does measuring on the bed improve on that?

I think that Tuan did a good job of explaining why in this article: http://www.largeformatphotography.info/fstop.html

Alan Davenport
6-Dec-2006, 19:06
Alan, check this out: http://www-unix.oit.umass.edu/~rbhome/focussummary.pdf

Ah, I missed the clarification that this was for the purpose of aperture selection and near/far focus. I do this using the built-in scale on the Tachihara; it's subdivided into 2mm chunks so it's not hard to find the near and far points.

Bob Gentile
7-Dec-2006, 13:13
Seems to me that this wouldn't apply when using tilts, swings, etc. Yes? No?

Alan Davenport
7-Dec-2006, 19:02
Seems to me that this wouldn't apply when using tilts, swings, etc. Yes? No?

If by "this" you mean the optimal f/stop selection, yes it does apply. Just measure how far the lens-to-film distance changes as you rack the focus between the nearest and farthest points of interest. ("Near" might refer to the top of a tree, while "far" is the base of the same tree, but it's still the amount of movement on the camera bed that determines the focus spread.)

Bob Gentile
8-Dec-2006, 14:47
Alan,

Thanks for clearing that up.