closest focusing distance with 270mm lens and 340mm bellows extension

[dirk_dom1]

<p>Hi!</p>

<p>I have a Linhof Technikardan 69 and i want to buy a 270mm lens.<br>

the Technikardan has max bellows extension of 340mm.<br>

How close can i get with it?</p>

<p>Is there a general formula (focal length, extension, closest distance) for this?</p>

<p>I'm looking for a Schneider 270mm.</p>

<p>Thank you,</p>

<p>bye,</p>

<p>Dirk Dom. </p>

[john_shriver]

<p>Given f = focal length, u = subject to lens distance, and v = film to lens distance,<br>

1 / f = ( 1 / u ) + ( 1 / v )<br>

Substituting in your two knowns:<br>

1/270 = 1/u + 1/340<br>

Gives you 131mm lens to subject distance.<br>

Now, 340mm isn't <em>really</em> the right number, you really need the distance from the film to the nodal point of the lens, which is probably in the middle of the lens, forward of the bellows. (There should be specifications of how far from lens board to the nodal point of the lens.)<br>

But 131mm is already pretty close, beyond having any useful depth-of-field.<br>

It's all there in the <a href="http://en.wikipedia.org/wiki/Focal_length">Wikipedia page on focal length</a>. That was the third match in a Google search for the words:<br>

focal length distance formula</p>

 

[Jochen_S]

<p>Schneider built a 270mm Telearton too. since it uses less draw than a standard lens design would for infinity you should be able to close up further with it.</p>

[Bill C]

<p>Hi John, it looks like a digit fell off your result somewhere along the line.</p>

<p>Instead of 131mm, the distance should be more like 1,311mm, a bit over 4 feet.</p>

<p>Also, like Jochen says, if it's a tele-lens, the rear nodal point/principal point will be farther forward than you might expect - possibly even in front of the lens - so the near focus could be closer than you would otherwise expect.</p>

[kparratt]

<p>The Tele Artons were favoured as portrait lenses and were produced concurrently with the Tele-Xenar. I have the 270 and 360 Tele Artons. They are pin sharp but lower contrast than the Tele-Xenar, which also have a much larger image circle.<br>

May I ask what the intended application is? Seriously, for very close up work you would be better off with a G-Claron<br>

I bought my Tele-Artons especially for portraits with 4x5 and 5x7 Linhofs.</p>