Focusing at 1:1 magnification

[unityofsaints]

Hi,

I haven't done any closeup work since I had a 4x5" Sinar about 7 years ago. What I did then was add an intermediate standard and second bellows to ensure I had double the bellows draw. It was a little fiddly to focus on such a long rail but I ended up with some decent still life closeups on FP3000b (R.I.P!).

Now I'm on a 8x10" Tachihara and trying to get some similar shots as the weather is too poor to head out for landscapes. Somewhat embarassingly, I can't get to that 2x focal length 1:1 magnification! What am I doing wrong? I have about 500mm of bellows so I should have enough to get either my 121mm or 180mm to focus, maybe not the 250mm but should be close, right? All I get on the ground glass is a very blurry and far away looking rectangle. As a workaround I am using my 480mm lens at the minimum focus distance but obviously that's not magnified enough.

What am I doing wrong? My understanding is that image circle increases closer than infinity so since all my lenses cover 8x10" I shouldn't have any problems there.

[Bob Salomon]

Hi,

I haven't done any closeup work since I had a 4x5" Sinar about 7 years ago. What I did then was add an intermediate standard and second bellows to ensure I had double the bellows draw. It was a little fiddly to focus on such a long rail but I ended up with some decent still life closeups on FP3000b (R.I.P!).

Now I'm on a 8x10" Tachihara and trying to get some similar shots as the weather is too poor to head out for landscapes. Somewhat embarassingly, I can't get to that 2x focal length 1:1 magnification! What am I doing wrong? I have about 500mm of bellows so I should have enough to get either my 121mm or 180mm to focus, maybe not the 250mm but should be close, right? All I get on the ground glass is a very blurry and far away looking rectangle. As a workaround I am using my 480mm lens at the minimum focus distance but obviously that's not magnified enough.

What am I doing wrong? My understanding is that image circle increases closer than infinity so since all my lenses cover 8x10" I shouldn't have any problems there.

If your camera is set for 1:1 for the lens you are using then move the camera towards or away from the subject until it is sharp. If you try focusing the front or rear standards then you will change the lens to film distance and not be 1:1.

[Mark Woods]

You can always use a diopter on your lens.

[Dan Fromm]

To expand a little on Bob's reply in post #2 above, the first thing to do is set extension to get the desired magnification. Set extension -- lens board to film plane distance is a very good approximation to 2* focal length. For the 121, 242 mm. For the 180, which will probably do better closeup, 360 mm. Then focus by moving the camera, as Bob suggested. Moving the standards (either or both) to focus will change magnification. Once you've got more-or-less good focus by moving the camera, you can move either standard a tiny bit (but no more) to get good focus. If you need exactly 1:1, check to make sure that you have it exactly -- put a ruler in your intended plane of best focus, verify that its image on the GG is the right size -- before shooting.

[Oslolens]

With a 4x5" you will cover 4x5" at 1:1. To cover the same 4x5" subject, use the 121mm lens at 484mm bellows and ca 242mm distance. Focus as described further up.

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[Dan Fromm]

With a 4x5" you will cover 4x5" at 1:1. To cover the same 4x5" subject, use the 121mm lens at 484mm bellows and ca 242mm distance. Focus as described further up.

Sent fra min SM-G975F via Tapatalk

Huh? At 1:1, film plane to subject distance is, neglecting internodal distance, 4*focal length, rear node to subject is 2*focal length and front node to subject is 2*focal length. Please check your arithmetic and assumptions.

[Oslolens]

Huh? At 1:1, film plane to subject distance is, neglecting internodal distance, 4*focal length, rear node to subject is 2*focal length and front node to subject is 2*focal length. Please check your arithmetic and assumptions.

You are right in your description, but wrong in the assumption: Thread is regarding 8x10", not 4x5". As a side note, I read Weston used a 210mm on a pepper picture. This was (miss) described as a wide angle in a discussion, but as it was macro-work, the angle of view was, by my calculations close to 210mm on 135-film.

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[Dan Fromm]

You are right in your description, but wrong in the assumption: Thread is regarding 8x10", not 4x5". As a side note, I read Weston used a 210mm on a pepper picture. This was (miss) described as a wide angle in a discussion, but as it was macro-work, the angle of view was, by my calculations close to 210mm on 135-film.

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I beg your pardon? The relationships between focal length, magnification and the relevant distances are independent of format.

[Oslolens]

I beg your pardon? The relationships between focal length, magnification and the relevant distances are independent of format.

Yes, agree. I see that I could have put in 8x10" in the sentence:If you are to cover the same 4x5" with 8x10" to make it clearer

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[Dan Fromm]

Yes, agree. I see that I could have put in 8x10" in the sentence:If you are to cover the same 4x5" with 8x10" to make it clearer

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More word salad and this

With a 4x5" you will cover 4x5" at 1:1. To cover the same 4x5" subject, use the 121mm lens at 484mm bellows and ca 242mm distance. Focus as described further up.

is still mistaken.