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Focusing with tilt
- Thread starter Grayhand
- Start date
The tape is crudely applied to keep focus exact. It's not really needed but I've put it there because I'm clumsy when fishing things out of my bag!
My 10x Silvestri was crap. Too much distortion. I wouldn't say this 12x has dramatically more mag but it's certainly sharper and far easier to use.
My 10x Silvestri was crap. Too much distortion. I wouldn't say this 12x has dramatically more mag but it's certainly sharper and far easier to use.
I mainly use my small 20x, but use my 10x as a tilting loupe, I've detached the base so I can use it as just as magnifying glass and tilt it.
Inspired by this and recent tilt threads I've updated my article on landscape focusing and added a new section "all-around tilt focusing technique" where I go through the typical iterative method, and go into some practical details around it. I may refine it further the coming days, but here it is:
How to focus a landscape scene
The key thing in it I think is the discussion about the near-point which often is hard to focus-peak on using the tilt-knob, as it often happens that the plane of focus turns close to the near-point, keeping it roughly in focus for a wide tilt range (so it's hard to see when you have the right amount of tilt!). You could get into arrangements when it turns around the far-point too, but at least my experience is that it's rare, and instead it's quite common that it turns close to the near-point so one often has to relate to the challenge that occurs.
Inspired by this and recent tilt threads I've updated my article on landscape focusing and added a new section "all-around tilt focusing technique" where I go through the typical iterative method, and go into some practical details around it. I may refine it further the coming days, but here it is:
How to focus a landscape scene
The key thing in it I think is the discussion about the near-point which often is hard to focus-peak on using the tilt-knob, as it often happens that the plane of focus turns close to the near-point, keeping it roughly in focus for a wide tilt range (so it's hard to see when you have the right amount of tilt!). You could get into arrangements when it turns around the far-point too, but at least my experience is that it's rare, and instead it's quite common that it turns close to the near-point so one often has to relate to the challenge that occurs.
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That brochure is a bit out of date - as the newest generation HR Rodenstocks (like the 90mm HR 'Alpagon') are not listed in it, and they are definitely best at wide open f5.6 to f8, and clearly degrade due to diffraction at f11.
If I have the time I'll post examples.
+1 ....I find best results in the f8-9.5 range, and 7-8 is nothing to sneeze at.
Damn... I thought I was quite good at tilting, but now when I've studied the subject further and learnt some details around axial tilt and realized the great advantage of placing the far-point along the tilt rotation axis I need to rewrite the section.
Sinar P has asymmetric tilt to make this a bit more practical, but the concept seems to work well with the center-axial Linhof Techno too. Just put the far-point in the horizontal center of the lens (if feasible), and then it's much easier and quicker to get to the desired placement of the plane of focus, hardly no need to iterate.
If far-point is off-center there's a big risk of getting to the problem that the PoF rotates close to the near-point and tilt-focus-peaking becomes near impossible, which is the case my article now goes into detail and how to work around. I need to keep that case too though, as it's not always feasible to actually place the far-point along the tilt rotation axis.
I've heard that some actually prefer to use base tilt that many of the old large format cameras had. Nowadays cameras have axial tilt, or at least approximately so. Can someone explain why this is the case? As far as I can see base tilt would only introduce problems in the tilt focusing process.
The film-to-sensor distance would increase when tilting, which could have some advantage to make iterative process faster in some focus distance / focal length combinations, but I would guess that it's unpredictable?
My own guess is that base tilt is solely about manufacturing - it's easier to manufacture such a mechanism, and some of those that have got used to work with it prefer it because they are used to it, rather than that there would be an actual workflow advantage with it.
The film-to-sensor distance would increase when tilting, which could have some advantage to make iterative process faster in some focus distance / focal length combinations, but I would guess that it's unpredictable?
My own guess is that base tilt is solely about manufacturing - it's easier to manufacture such a mechanism, and some of those that have got used to work with it prefer it because they are used to it, rather than that there would be an actual workflow advantage with it.
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Here's a good article from the Ebony website about asymmetrical rear tilt, which is a fairly easy read. Again it emphasises that if you can put the axis of tilt across the far focal point then it makes life easier, since when you tilt the lens (with on axis tilt) the distance between the lens and film plane doesn't change. Obviously this was easier to achieve with rear asymmetrical tilt since you could move the axis of tilt (for the film plane) up and down and place it across the far focus point, wherever you decided it was, and then tilt the rear to change the angle of the plane of focus - but the principle is still applicable (to a degree) if you're willing to use rear rise-fall to make sure the axis of tilt falls across the far focus point.
jotloob
Subscriber Member
If you dislike the mathematical approach and are in trouble with the imagination of virtual POF and where to focus (as I do) here is a good supplement for your thumb rules and experience .
Unfortunately , it is based on GG focusing and control , which I find a pain on the small GG as well .
http://www.alpa.ch/dms/products/tools/alpa-tilt-paper/ALPA_Tilt-201206_E.pdf
Leica Geo Systems , the maker of the DISTO 5 , should make a hand held TILT/SWING meter , similar to a hand held light meter .
Ok . . . I know , this will always be a dream . :ROTFL: . . Unfortunately .
Unfortunately , it is based on GG focusing and control , which I find a pain on the small GG as well .
http://www.alpa.ch/dms/products/tools/alpa-tilt-paper/ALPA_Tilt-201206_E.pdf
Leica Geo Systems , the maker of the DISTO 5 , should make a hand held TILT/SWING meter , similar to a hand held light meter .
Ok . . . I know , this will always be a dream . :ROTFL: . . Unfortunately .
Yes I've finally starting to understand the merits of axial tilts and have started to use them on my Techno whenever I can place the far-point there (speeds up focusing workflow).
On the Techno like most modern more compact cameras the tilt axis is in the center, but I think that in quite many cases it's feasible to have the far-point along the horizontal center without getting too close to the near-point. Once focused one can make a final refinement step with a far-point placed off-axis farther away, refinement is easy when one is "almost there" at the start.
However with old-school base tilt the tilt axis is outside the frame, that can surely not be any advantage in any case? Not sure which cameras that actually have base tilt though, haven't seen many of them...
On the Techno like most modern more compact cameras the tilt axis is in the center, but I think that in quite many cases it's feasible to have the far-point along the horizontal center without getting too close to the near-point. Once focused one can make a final refinement step with a far-point placed off-axis farther away, refinement is easy when one is "almost there" at the start.
However with old-school base tilt the tilt axis is outside the frame, that can surely not be any advantage in any case? Not sure which cameras that actually have base tilt though, haven't seen many of them...
jotloob
Subscriber Member
For those of you , who have the SILVESTRI 12x loupe .
The mechanical movement of the focusing ring is far too smooth .
That is very annoying when working with the loupe .
Now , I have found a solution for this issue , which I would like to show you .
It is a very simple thing . A rubber O-ring .
Please have a look to the attached image .
The rubber ring prevents the focusing ring from moving , but does not block the ring .
Just makes the erroneous turning difficult , but can still be adjusted .
View attachment 71877
The mechanical movement of the focusing ring is far too smooth .
That is very annoying when working with the loupe .
Now , I have found a solution for this issue , which I would like to show you .
It is a very simple thing . A rubber O-ring .
Please have a look to the attached image .
The rubber ring prevents the focusing ring from moving , but does not block the ring .
Just makes the erroneous turning difficult , but can still be adjusted .
View attachment 71877
