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Focusing Issues

 
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wiux



Joined: 04 Jun 2019
Posts: 36

PostPosted: Wed Nov 10, 2021 1:13 pm    Post subject: Focusing Issues Reply with quote

This might be the stupidest of my questions so far, but I just noticed I can't seem to get a tack sharp image using a Metz flash even after stopping down & shooting at a distance (respectively anywhere between f/8-16 & 10 to 25'). I have been able to get very sharp images in the past (at a macro bellows expansion at f/32 using the same flash & handheld), but I'm truly stumped by my most recent negatives.

I was willing to concede it was just ineptitude at first (not least in part because most of my shots are at night & I'm prefocusing & in front of the camera when the shutter fires), but the most recent results are baffling. According to my depth of focus chart, I should have a focal plane of around 20', much more than enough to have everything fall into the plane, yet nothing's truly sharp when viewed under the loupe, even though I used the same loupe to focus on the ground glass on a lantern before taking its place while setting up the shot.

Another curiosity is I tried swapping a Rodenstock Optar out for the Wollensak I've been using to see if it'd make a noticeable difference (it was the only other lens I had on hand) but despite both being marked at 135mm, the ground glass focus is dramatically off: at a distance of 8', the Rodenstock is in focus at ~6' (the Wollensak focuses as one would expect, perhaps also because the camera body is calibrated to the W. & not the R.). I did notice the R.'s rear element sits a bit more flush than the W., which explains the discrepancy somewhat (although I still don't understand why two lens of the same focal length should be so different) & its aperture is marked f/4.5 vs. the W.'s f/4.7.

Oddest of all is out of the batch of negatives I inspected, the long exposures are the sharpness I expect out of 4x5, when in theory the flash should be just as sharp, if not sharper (due to its ability to freeze motion & being stopped down more) & because the shots from this batch were all taken on a tripod. Again, maybe I'm just making stupid mistakes, but the depth of focus really boggles me because it doesn't make sense. Does anyone have any ideas? I'm tearing my hair out trying to explain this :/

Edit: I've a theory the camera's slowly turning while sitting on the tripod plate due to the combined weight of the camera & flash & because the screw hole for the Metz is very off center. Overlapping some negatives confirms a difference in composition, but I also can't remember whether I took the camera off the head to tighten the screw in between shots. This is somewhat of an explanation, because the long exposures were taken using the camera body's screw, which is centered, rather than the flash's. But I'm still unconvinced it accounts for the focal plane failure.
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45PSS



Joined: 28 Sep 2001
Posts: 4051
Location: Mid Peninsula, Ca.

PostPosted: Wed Nov 10, 2021 8:39 pm    Post subject: Reply with quote

1. lens are rarely their marked focal length. they are commonly 2 to 3 millimeters either side of the marked focal length and may be more depending on the manufacturers tolerance.
2. this is the lists of cams for the Pacemaker Graphics
https://graflex.org/speed-graphic/top-rangefinder-cams.html

By having the Metz mounted in the camera body tripod socket and the Metz socket connected to the tripod you are likely getting camera shake from tripping the shutter and or vibration of the shutter operating.

Some tripods transmit vibrations.
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wiux



Joined: 04 Jun 2019
Posts: 36

PostPosted: Wed Nov 10, 2021 11:58 pm    Post subject: Reply with quote

It has nothing to do with cams or the rangefinder. I'm using only the ground glass for focusing for these.

I'm not sure what you mean by camera shake. I don't think it's camera shake in the usual sense because the shutter speeds (with flash) are too fast to be affected by shake. If anything, the long exposures were sharper than the flash photos.
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45PSS



Joined: 28 Sep 2001
Posts: 4051
Location: Mid Peninsula, Ca.

PostPosted: Thu Nov 11, 2021 12:42 am    Post subject: Reply with quote

I too have a Metz handle flash. Its connection to the camera is stable handheld, attached to a tripod the camera is less stable.
A rough running shutter can/will induce vibration regardless of speed.
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wiux



Joined: 04 Jun 2019
Posts: 36

PostPosted: Thu Nov 11, 2021 2:20 am    Post subject: Reply with quote

I see. How did you get around this problem?
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45PSS



Joined: 28 Sep 2001
Posts: 4051
Location: Mid Peninsula, Ca.

PostPosted: Thu Nov 11, 2021 3:31 am    Post subject: Reply with quote

If I'm going to use the Metx I use it hand held. A good solution would be get a second economy tripod to put the Metx on.

I have a pair of Flashpoint 300 watt second studio strobes and light stands similar to https://www.adorama.com/fplfs300bk1.html and umbrellas.

With the bellows extended to 6 foot focus, front standard locked, focus lock set can you move the front standard by pressing on it? If it moves the standard lock needs to be adjusted.
Is there any side play in the rails?
Is the bed solid to the body?
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wiux



Joined: 04 Jun 2019
Posts: 36

PostPosted: Thu Nov 11, 2021 4:31 am    Post subject: Reply with quote

Ah, sadly I'm biking around with equipment so I'm limited to what fits in a milk crate & weight I can still pedal. Compactness was the draw of using the Metz over contemporary speed lights (well that & it's terrific strength for a good price).

Yeah, everything's solid. The weak link is the tripod screw, but I think I'll use a coin to tighten it further this time & maybe that'll do the trick. I'm still unsure why the depth of focus didn't save me, but I'll give it more of a think later.
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45PSS



Joined: 28 Sep 2001
Posts: 4051
Location: Mid Peninsula, Ca.

PostPosted: Thu Nov 11, 2021 4:58 am    Post subject: Reply with quote

Make sure the band on the Metz is tight also.
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