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Kodachrome25
30-Apr-2014, 16:36
In the first year I used LF, I mostly used front axis tilt or swing to avoid any changes in perspective, not much rear which is base only on the tilt and axis or base on the swing. One thing I noticed readily in my landscape work is that if I used a fair amount of either on the front and depending on what lens I was using, the sharpness would deteriorate anywhere from a bit to a lot. So I started using combos of a little front and mostly back tilt and have seen a remarkable difference in image quality, I now get *much* sharper images by not swinging that image cone around so much.

It seems logical to me that if you change the front swing, you are changing the optical path of the lens a little or a lot depending on the amount. But if you use rear adjustments, you are only changing the focus and perspective so the lens is not being pushed so hard at the edges. I am kind of surprised to not see this mentioned anywhere so I am wondering if anyone has some thoughts on it…or am I just crazy?

I thought about putting this in the camera section but this is really about the lens being pushed too hard or not, mods feel free to move it if the other section if a better fit...

Erik Larsen
30-Apr-2014, 16:52
Not sure if this applies to your situation, but if you use front movements to the extreme you might end up at the limits of the lens' coverage where the optical quality is lowest. Using rear movements you won't face that same dilemma unless rise or shift is used. I usually only use rear movements as my arms are not long enough to use front movements comfortably. That being said, my subject matter usually doesn't care about straight lines or weird perspectives.

djdister
30-Apr-2014, 17:01
You are mixing apples and oranges. You would not substitute rear tilt for front tilt - they have very different objectives. For example, front tilt would be used for altering the plane of focus, while rear tilt would be used for correcting converging vertical lines (altering the shape of the subject).

A guide to using view camera movements would explain this in greater depth.

Kodachrome25
30-Apr-2014, 17:22
You are mixing apples and oranges. You would not substitute rear tilt for front tilt - they have very different objectives. For example, front tilt would be used for altering the plane of focus, while rear tilt would be used for correcting converging vertical lines (altering the shape of the subject).

A guide to using view camera movements would explain this in greater depth.

I have Steve Simmons guide so I have employed in the past the decisions based on what to use on that and what you have stated above...

But what I am finding is depending on the lens in use, altering the angle of the projected optical path as one can do in using front VS rear tilt, the image quality can degrade, sometimes even with a little bit of movement on a lens with plenty of image circle like a Fuji 240 A for example. I don't see anything in Steve's book addressing the loss of sharpness...so I found it really interesting and *very* consistent in using rear VS front tilt for maximum image quality...

Sal Santamaura
30-Apr-2014, 17:26
...I am kind of surprised to not see this mentioned anywhere so I am wondering if anyone has some thoughts on it…or am I just crazy?...I'm feeling a little lazy right now, so won't do the searching, but it's been mentioned in any number of places. Probably in Adams' basic series as well as the archive here and elsewhere. :)

No, you're not crazy. Your observations are absolutely correct. You've progressed as a view-camera photographer the best way possible, namely self-teaching. Keep on going!

StoneNYC
30-Apr-2014, 17:32
Are you adjusting your front movements and compensating with any rise or drop movements?

Kodachrome25
30-Apr-2014, 17:35
Are you adjusting your front movements and compensating with any rise or drop movements?

Regards to rise and fall or shift, never really to compensate, only to fine tune compositions and always with consideration of usable image circle. One night I spent a bunch of time creating a spread sheet that tells me how much I can push each lens before running out of coverage, that has helped a lot, I keep it on my phone.

vinny
30-Apr-2014, 17:35
"You are mixing apples and oranges. You would not substitute rear tilt for front tilt - they have very different objectives. For example, front tilt would be used for altering the plane of focus, while rear tilt would be used for correcting converging vertical lines (altering the shape of the subject)."
I disagree.

I use a combo of movements all the time in my landscape work, Especially 8x10 where it's hard to reach the front standard w/o smashing my face against the ground glass. I usually start with a bit of front tilt right after composing the shot, then proceed to dial in focus from the rear standard. Yes, this uses more the sweet spot of the lens. or whatever, you know what I mean.

StoneNYC
30-Apr-2014, 17:53
Regards to rise and fall or shift, never really to compensate, only to fine tune compositions and always with consideration of usable image circle. One night I spent a bunch of time creating a spread sheet that tells me how much I can push each lens before running out of coverage, that has helped a lot, I keep it on my phone.

You may be at the edges often, instead of using the center of the lens, this might be part of your sharpness issue.

If you know you will be using the edges of the lens, try pre-composing the image improperly by using the rise or fall, and then tilt etc, or compensate the rise/fall during composition, either way, try and keep the light path hitting the film more in the center of the lens.

Joel Truckenbrod
30-Apr-2014, 18:04
You are mixing apples and oranges. You would not substitute rear tilt for front tilt - they have very different objectives. For example, front tilt would be used for altering the plane of focus, while rear tilt would be used for correcting converging vertical lines (altering the shape of the subject).

While I understand this in principle, I disagree with it in practice within the context of landscape work.

Using rear tilt is perfectly valid for altering the plane of focus. Assuming a given composition isn't negatively impacted by the distortion induced by rear tilt (some are, but many are not), I almost always prefer it. Why? A few reasons. You're more likely to use the center of the image circle, there is more image circle left to work with if rise/fall is desirable, and finally the slight enlargement of the foreground can increase the perception of depth, even with longer lenses. My rule is to simply judge what is necessary by the aesthetic requirements of the image. There is no need to follow simplified "rules" as dogma, use your eyes to see what visually works best and to inform your future choices.

Erik Larsen
30-Apr-2014, 18:09
While I understand this in principle, I disagree with it in practice within the context of landscape work.

Using rear tilt is perfectly valid for altering the plane of focus. Assuming a given composition isn't negatively impacted by the distortion induced by rear tilt (some are, but many are not), I almost always prefer it. Why? A few reasons. You're more likely to use the center of the image circle, there is more image circle left to work with if rise/fall is desirable, and finally the slight enlargement of the foreground can increase the perception of depth, even with longer lenses. My rule is to simply judge what is necessary by the aesthetic requirements of the image. There is no need to follow simplified "rules" as dogma, use your eyes to see what visually works best and to inform your future choices.

Well said, I agree wholeheartedly.

Bill_1856
30-Apr-2014, 18:09
When I first read the topic heading I thought that you were really stupid. Then read the post and thought about it, and concluded that you're absolutely correct. My bad. Thank you (with apologies)!

Kodachrome25
30-Apr-2014, 18:25
You may be at the edges often, instead of using the center of the lens, this might be part of your sharpness issue.

If you know you will be using the edges of the lens, try pre-composing the image improperly by using the rise or fall, and then tilt etc, or compensate the rise/fall during composition, either way, try and keep the light path hitting the film more in the center of the lens.


I generally agree with what you are saying, but with lenses like the 240 and 350 I am rarely at the edges of the image circle but see uniform image degradation with front tilt. I often have to work really fast for fleeting light so the pre-correction thing is not likely a route I will take, I try to work with as little movements or iterations of such as possible.

So far, using mostly rear tilt is allowing me to nail it super fast and sharp, I'll stick with a combo of that and a little front tilt.

I like the discussion though, I went out not long ago to get my annual Earth Day photos and really enjoyed using the 4x5, experience always pays off and the eye can really get to work when the tech stuff is a lot more soundly & confidently versed...

Erik Larsen
30-Apr-2014, 18:35
Dan, with the lenses you are referencing I can't believe you are could be running out of coverage on 4x5. The only explanation I can think of why you are seeng a difference between front and rear tilt is that you might be tilting more than is needed with the front and not realizing it. I'm not questioning your competence, but a tiny bit of tilt goes a long way, especially in landscape situations. That being said, if it looks good on the ground glass that's all that matters-front or rear tilt, use what works best for and your eyes:)

sanking
30-Apr-2014, 19:05
With front tilt or swing the correction requires less physical movement than the rear (assuming the front board is about 1/2 as small as the rear) so it is quite easy to under or over-correct with front swing. Assuming you make the adjustment correctly I don't see that it would make any difference in terms of absolute sharpness over the entire field, and never observed this in my own work, with the obvious caveat that you can lose the sweet spot of the lens much quicker with front swings than rear swings.

On the other hand, if I have enough coverage my preference is to place the rear standard level and at right angle to the subject and adjust whenever possible with front rise and fall, or front shift and tilt. Course, if you need dramatic correction for perspective you will eventually run out of movements on the front and have to use the back as well.

With a view camera there are often several adjustments that give an equivalent result.

A classic book on the use of the view camera is View Camera Technique by Leslie Stroebel.

Sandy

David Lobato
30-Apr-2014, 19:28
Some good investigating K25. When I was new with 4x5 many years ago, I ran a series of tests on an arrangement of my kid's LEGO blocks with front tilts versus rear tilts. I had been reading Fred Picker's articles on view camera movements and decided to find out for myself. The test was all on Polaroid Type 52 instant B&W prints (RIP). An excellent learning exercise as it turned out. As Joel said, the rear movements emphasize the foreground objects, and it was confirmed on the Polaroids. Being Polaroids, relative sharpness couldn't be compared. As a result I use front or rear or both when the circumstance calls for it. Rear tilts and swings are easier on 8x10, and especially on 11x14, because of the long bellows extensions.

Kodachrome25
30-Apr-2014, 20:08
I'm glad people are adding as much as they are, when it comes to movements, a little bit does seem to go a long way but there is such nuance in all of it, easy to get carried away. For what it is worth, I only use 4x5, lenses are 65, 90, 120 macro, 135, 180, 200, 240 and 350, all top quality modern plasmats, most with lots of coverage.

Doremus Scudder
1-May-2014, 03:34
Kodachrome25,

You are checking focus at top and bottom when you use tilts and on both sides when using swings aren't you? I know it's a stupid and obvious question, but I can't think of anything else that could be causing your problem.

Theoretically, the camera itself is a "black box" as far as lens and film are concerned. The only thing that matters is the orientation of lens to film plane, regardless of how that is achieved. I could easily make exactly the same set-up with front tilt or back tilt; same with swings.

As Sandy mentions, the amount of front tilt/swing you need will be physically smaller if the lens standard is much smaller than the back, but, if you are checking focus and doing your iterations, you would be correcting for that by seeing that you have overcompensated.

Since tilting or swinging either the back or the lens standard moves the plane of sharp focus around. Normally, one has an idea of what one wants in (or out) of focus before applying movements and just enough movement is applied to do the job. I always have focus points top and bottom when I tilt and on each side when I swing to check. I'm assuming you are doing the same, and adjusting focus while applying the movements. The techniques are slightly different for base and axis movements, but the result is the same. Again, the camera is just a black box...

With the lenses you mention, there should not only be adequate coverage for lots of movements, but edge sharpness should be acceptable as well out to the point of vignetting. So, I can really only assume that your problem is due to lack of sharp focus, either from not checking after the movements have been applied, or from not being aware of, and not checking focus for the displaced plane of sharp focus top/bottom or left/right after applying the movement.

Let us know how you do solving this glitch. However, keep in mind that it should not matter if you use front or back movements.

Best,

hoffner
1-May-2014, 04:15
I'm feeling a little lazy right now, so won't do the searching, but it's been mentioned in any number of places. Probably in Adams' basic series as well as the archive here and elsewhere. :)

No, you're not crazy. Your observations are absolutely correct. You've progressed as a view-camera photographer the best way possible, namely self-teaching. Keep on going!

As several P's correctly said, there is no optical reason on Earth why front movements should introduce worsening of optical quality of the image as opposed to back movements. Of course, provided the image circle itself holds decent image quality inside its limits.

Kodachrome25
1-May-2014, 07:28
Doremus, yep, doing all that you mentioned and agree. Hoffner, while I agree and thought the same my self, the simple notion that the change in the angle of the projected image coming in with a front tilt/swing VS no change with rear tilt aslo makes sense to me from a standpoint of a lens's given "Sweet spot".

Like I said, all my lenses are top notch at the moment so I can use some less expensive film and play around with it some more when time permits. All in all thanks for weighing in, at least it is a hurdle I am learning to work my way around in and if the images are coming out as improved by employing some modifications in the way I work, well at least for now when I simply have to get the shot right, it's good to know I will.

Kirk Gittings
1-May-2014, 07:39
Long shot.........as you seem to be saying that there is a general degradation of sharpness rather than that an increase towards the lens edge where coverage begins to fall off.........I don't suppose it has to do with a common small aperture you tend to use with each lens in a given situation ie reaching diffraction limitations?

Kodachrome25
1-May-2014, 08:03
Long shot.........as you seem to be saying that there is a general degradation of sharpness rather than that an increase towards the lens edge where coverage begins to fall off.........I don't suppose it has to do with a common small aperture you tend to use with each lens in a given situation ie reaching diffraction limitations?

I wondered that too but in one case with the 350 Apo Tele Xenar F11 it was noticeable in going from front to back and using the same good working aperture of F22 &1/2. Same type of easy tilt only shot. The first shot was a portion of a waterfall above me, front tilt only and came out a bit soft and then last week a creek with the closest portion 15 feet away and the furthest over 200 feet away, mostly back tilt and a little front, critically sharp.

Who knows, maybe since the front was pointed up so high for the waterfall shot the focus drifted back, it might have still been in the looser Winter mode.

I'll play with it some more and see what comes of it....

mdarnton
1-May-2014, 08:17
I think this is what Mr. K-chrome is talking about? As has been mentioned, without something like a building in the picture, the perspective effect might be invisible and irrelevant.

Tilting the lens tilts the cone of sharpness relative to the film, and brings the edge of the lens' field into use. If a lens has a problem, it's going to be near the edge, right?

Tilting the film keeps the film within the center of the lens' coverage.


http://i1.minus.com/jJdDtKWnP6r0p.jpg

Drew Wiley
1-May-2014, 08:33
Numerous times in "typical" landscape situations you mainly need just some kind of tilt for near/far plane of focus. Since the camera is often pointed a bit downward
anyway, using the rear tilt actually gives a truer visual effect if the tilts are going to be significant. And this is the better way to go if you lens have limited coverage. But I always also base things on exactly how I want the composition to look - not only in focus, but shape-wise.

Sal Santamaura
1-May-2014, 08:41
As several P's correctly said, there is no optical reason on Earth why front movements should introduce worsening of optical quality of the image as opposed to back movements. Of course, provided the image circle itself holds decent image quality inside its limits.Dan is enlarging up to 20x24" through a 150mm Apo Rodagon N. Researching MTF curves for the camera lenses he's using would show a distinct falloff in modulation percentage with distance from their image circles' centers. That is the reason why front movements, which displace the film from his lenses' optical axes, result in less print sharpness than do rear movements, which keep things centered on the axes. He's asking a lot of his system. A number of other posters refer to "coverage," but most of them mainly make contact prints, so illumination is their primary concern, not sharpness. The demands on camera lens performance is six times less for contact prints than when a 6X magnification enlargement is the goal. Assuming similar printing paper resolution, not rough-surface alternative process papers, which ask even less of the camera lens.


...Who knows, maybe since the front was pointed up so high for the waterfall shot the focus drifted back, it might have still been in the looser Winter mode...What is "Winter mode?"

Sal Santamaura
1-May-2014, 08:50
I think this is what Mr. K-chrome is talking about? As has been mentioned, without something like a building in the picture, the perspective effect might be invisible and irrelevant...Your drawing is close, but Dan isn't placing his film outside the circle of illumination. Rather, he's putting it outside the area where his lenses' performance is superlative enough to satisfy the demands of 6X enlargements. Things generally get mushy before they get dark. :)

mdarnton
1-May-2014, 08:54
Yes, I know--I was just exaggerating to make the point of what was happening. Notice that I called it the "cone of sharpness", not the cone of coverage. :-)

Sal Santamaura
1-May-2014, 09:11
Yes, I know--I was just exaggerating to make the point of what was happening. Notice that I called it the "cone of sharpness", not the cone of coverage. :-)Yes, you're right. I just hope readers don't interpret the drawing incorrectly, as they frequently do. :D:D

hoffner
1-May-2014, 09:46
Dan is enlarging up to 20x24" through a 150mm Apo Rodagon N. Researching MTF curves for the camera lenses he's using would show a distinct falloff in modulation percentage with distance from their image circles' centers. That is the reason why front movements, which displace the film from his lenses' optical axes, result in less print sharpness than do rear movements, which keep things centered on the axes. He's asking a lot of his system. A number of other posters refer to "coverage," but most of them mainly make contact prints, so illumination is their primary concern, not sharpness. The demands on camera lens performance is six times less for contact prints than when a 6X magnification enlargement is the goal. Assuming similar printing paper resolution, not rough-surface alternative process papers, which ask even less of the camera lens.

What is "Winter mode?"

But then, (enlarging 6x) the Coc is also bigger and you use a bigger viewing distance so the perceived sharpness is the same. You cannot mix apples and oranges and then make incorrect conclusions in the optical theory out of the mixture. Using the part of the lens coverage with less quality gives pictures with - well, less optical quality. Big deal.

Drew Wiley
1-May-2014, 09:48
Sharpness is sharpness. "Perceived sharpness" means you need reading glasses. Not all of us subscribe to that "normal viewing distance" BS.

hoffner
1-May-2014, 09:58
Sharpness is sharpness. "Perceived sharpness" means you need reading glasses. Not all of us subscribe to that "normal viewing distance" BS.

Perceived or real, it doesn't change anything on the logic. If you use the part of the image circle with less optical quality you get - well, a picture with less optical quality. Is that so surprising?

Sal Santamaura
1-May-2014, 09:59
But then, (enlarging 6x) the Coc is also bigger and you use a bigger viewing distance so the perceived sharpness is the same. You cannot mix apples and oranges and then make incorrect conclusions in the optical theory out of the mixture...Optical theory is frequently ignored by viewers of large prints made from LF negatives. The old "nose on the glass" thing. My post reflected that reality.


...Using the part of the lens coverage with less quality gives pictures with - well, less optical quality. Big deal.I suspect it is a big deal to Dan, or he wouldn't have started this thread.

Drew Wiley
1-May-2014, 10:43
Another reason to prefer rear tilts would be due to simple mechanical vignetting during focus itself at larger apertures. Just another tool to be intelligently employed.

Eric Leppanen
1-May-2014, 10:46
Jack Dykinga, in his book Large Format Nature Photography, speaks of frequently using rear tilt as an aesthetic choice to emphasize the foreground of near-to-far compositions, or to work around the coverage limitations of wide angle lenses. Rear tilt is also frequently preferred when using very long lenses; when using my 1200mm telephoto lens on my 8x10 camera, for example, rear tilt was a must since my arms weren't long enough to reach the front standard comfortably while focusing.

I think the increased sharpness from rear tilt you are seeing stems from staying closer to the "sweet spot" of the lens image circle, as well as minimizing the amount of off-axis light coming through the lens (which will be a benefit even with lenses with huge coverage). The trade-off, of course, is managing the distortion that rear tilt introduces into the image.

Brian C. Miller
1-May-2014, 11:06
#1, rear tilt doesn't change the plane of focus.
#2, the plane of focus can only be changed by changing the angle of the lens in relationship to the subject.

This simply comes down to tilting the whole camera, i.e., use it like a box camera, and then adjusting things.

Kodachrome25, are you using a loupe when you focus? What you may want to do is use a test target, any type will do, and make a series of test shots. Place the targets so you can see them in the corners and center, and then put a sign in the scene denoting the f/stop and the angle of tilt.

Drew Wiley
1-May-2014, 11:11
Long bellows aren't an issue. Lamarck was right. Just measure your arm length before and after about twenty years of working with a long bellows.

cowanw
1-May-2014, 13:34
Only if your children have longer arms.

Long bellows aren't an issue. Lamarck was right. Just measure your arm length before and after about twenty years of working with a long bellows.

Kodachrome25
1-May-2014, 14:29
What is "Winter mode?"

On the Chamonix 45N-2, there is a nylon tipped allen head set screw by the focus knob that can be adjusted for focus tension. I tend to use it a tiny bit looser in the Winter since temps can get below zero and all bearing surfaces, not just those with lube, can get a little stiff.

In the other three seasons I tighten it back up to where it does not drift if pointed down for macro work, the same would apply if it were pointed up at a steep angle. I have thought about putting some kind of lock knob on it, but that would require me to drill into the assembly and tap it and I am a bit reluctant to do that for obvious reasons.

And for what it is worth, I appreciate *all* the opinions given here and especially the inclusion of other printed reference material, thanks a bunch guys!

ROL
1-May-2014, 15:43
Only if your children have longer arms.

Long bellows aren't an issue. Lamarck was right. Just measure your arm length before and after about twenty years of working with a long bellows.

You see now, this is why I like this forum, because of proper application of the Theory of Intelligent Nonsense.

Drew Wiley
1-May-2014, 16:15
The mere existence of large format photography proves that irrationality is a valuable trait which can be transmitted from one generation to another. We'd probably
even survive another "extinction-event" asteroid impact, at least in the sense that all our remaining film would probably be exposed for posterity, once that evolves from our leftovers.

Sal Santamaura
1-May-2014, 16:40
...Chamonix 45N-2...I have thought about putting some kind of lock knob on it, but that would require me to drill into the assembly and tap it and I am a bit reluctant to do that for obvious reasons...So Dick Phillips was spot on when he told me, with respect to Chamonix copies of his design, that they were better in some ways but had two drawbacks. Dick found fault with their lack of handles and omission of a focus lock. :)

ROL
1-May-2014, 17:22
The mere existence of large format photography proves that irrationality is a valuable trait which can be transmitted from one generation to another. We'd probably
even survive another "extinction-event" asteroid impact, at least in the sense that all our remaining film would probably be exposed for posterity, once that evolves from our leftovers.

We're just dinosaurs who don't know were dead yet. BTW, the Theory I expressed was intended to refer to any or all LFPF discussions, but you can take it any way you want.;)

ic-racer
1-May-2014, 17:23
#1, rear tilt doesn't change the plane of focus.
#2, the plane of focus can only be changed by changing the angle of the lens in relationship to the subject.

.

The subject has nothing to do with the plane of focus. The subject neither cares nor knows how the camera is set up. The plane of focus is dependent on the relationship between the lens and film.

Brian C. Miller
1-May-2014, 20:09
Yeah, I know, we're discussing the Scheimpflug principle (http://www.waldonell.com/photos/photography-articles/focusing-normal-and-tilt-swing-lenses/). Pardon me for using a slight misnomer instead of perfectly quoting from the literature.

http://www.waldonell.com/workspace/uploads/lens_focus_planes4.png

Still, it isn't the back tilt that controls focus. And Kodachrome25 needs to run some specific tests for himself, to see how it works and what performance characteristics his equipment has.

Tim Meisburger
1-May-2014, 20:28
Well, I'm confused, except about Lamarkian evolution, which was recently proved, as such things that have been previously disproved often are:)

hoffner
2-May-2014, 01:43
Who knows, maybe since the front was pointed up so high for the waterfall shot the focus drifted back, it might have still been in the looser Winter mode.



I think you have probably answered your own original question.

Doremus Scudder
2-May-2014, 02:25
#1, rear tilt doesn't change the plane of focus.
#2, the plane of focus can only be changed by changing the angle of the lens in relationship to the subject. ...

I beg to differ:

The relationship of the three planes, plane of focus, lens plane and film plane have a well-defined relationship. When film and lens planes are parallel, the plane of sharp focus is also parallel to them. When either the film or the lens plane are moved from parallel, the three planes will meet in a line somewhere. It doesn't matter if the lens movement or the back movement is used, Scheimpflug still applies. Pointing the camera down and using back tilt can yield exactly the same lens plane/film plane relationship as keeping the camera level and using front tilt. In both cases, the plane of sharp focus changes position in exactly the same way in relation to a parallel configuration. The back relation to the subject controls the perspective of the projection, moving the lens in relation to the subject does not.

Back on topic now:

The published specs I see for Dan's Fuji A 240 show rather consistent sharpness and MTF from center to edge... I agree that many lenses perform worse at the outside of their image circles, but with this lens, at least, the difference should be slight enough that even at 20x24 the print quality should be very, very good.

I'm still at a loss as to what the problem is here. A possible test would be to find a rather homogenous subject with lots of fine detail (say a wheat field, brick wall, etc.) and use front tilt to bring everything into focus, intentionally using the extreme outside of the image circle by using as much front rise as the lens will allow. Then, using front fall, shift the image to another part of the subject, this time as much closer as possible to the optical center of the projected image circle while at the same time tipping the camera back a bit to retain as much of the original framing as possible (note, this is essentially the same as using back tilt, just accomplished by using fall and front tilt, but keeping the tilt on the front standard). Develop, check sharpness and see if, indeed, it is the edge of the image circle that is causing the apparent softness.

Also, if it were the outside of the image circle that were causing the lack of sharpness, it should/would also show up in shots using lots of rise/fall, in which the edge of the image circle were used for much of the recorded image, e.g., the top of a skyscraper shot with lots of front rise and the standards otherwise parallel. One should check that as well to confirm the hypothesis.

If the problem is focus creep, as Dan mentions as a possibility, then test conditions should be structured to eliminate that variable :)

That said, if focus creep is the problem , then it should be limited to situations that cause it (pointed camera, compressed bellows; I've had this happen from very compressed bellows pushing the standards apart a bit before I was able to fire the shutter...). It should not appear in shots with the camera level and no force trying to displace focus. It might be worth checking the negs for this scenario as well.

Best,

Doremus

hoffner
2-May-2014, 03:43
That said, if focus creep is the problem , then it should be limited to situations that cause it (pointed camera, compressed bellows; I've had this happen from very compressed bellows pushing the standards apart a bit before I was able to fire the shutter...). It should not appear in shots with the camera level and no force trying to displace focus. It might be worth checking the negs for this scenario as well.

Best,

Doremus

One can also displace focus unintentionally by applying the very tilts to the front standard if it is sufficiently free.

Kodachrome25
2-May-2014, 06:34
I think you have probably answered your own original question.

Maybe in that particular case, which is the only one that would have induced focus creep. Like I said in other posts, when I feel like commiting the time and resources, I will explore it with a series of controlled tests. But for now, I need to get to work on making solid images. My wife and I are loading our solar powered pickup camper at the moment, we will be off the grid for the week, so I'll return to this topic in a little while...

Drew Wiley
2-May-2014, 08:40
ROL - we're too primitive to be dinosaurs. We LF types are more like crocodiles and turtles. We existed before the dinosaurs and will outlast them. The dinosaurs are
all the frilly gotta-have comsumer electronics digi types, who will spend a ton of money on something that goes obsolete every five years. Turtles and crocodiles are
more basic designs that just make sense, and always have.

hoffner
2-May-2014, 08:52
Maybe in that particular case, which is the only one that would have induced focus creep. Like I said in other posts, when I feel like commiting the time and resources, I will explore it with a series of controlled tests. But for now, I need to get to work on making solid images. My wife and I are loading our solar powered pickup camper at the moment, we will be off the grid for the week, so I'll return to this topic in a little while...

I'm sure you will find the cause and it will be less magic than you ever thought. Have a good trip!