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03-26-2010, 12:17 PM   #31
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Interesting, do you have any links that explains the optics in detail about it?

The tilting of the focal plane is pretty easy for me to understand, but the shift isn't. What exactly is gained by decoupling the image circle from the sensor plane?


Last edited by Eruditass; 03-26-2010 at 12:22 PM.
03-26-2010, 12:31 PM   #32
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QuoteOriginally posted by Eruditass Quote
Interesting, do you have any links that explains the optics in detail about it?

The tilting of the focal plane is pretty easy for me to understand, but the shift isn't. What exactly is gained by decoupling the image circle from the sensor plane?
Start with this site: Using Tilt-Shift Lenses to Control Perspective

Edit: Also go to this link and at the top of page 2, it explains why moving the whole camera is the best solution to your previous question.

http://cpn.canon-europe.com/content/education/infobank/lenses/tilt_and_shift_lenses.do

Last edited by Blue; 03-26-2010 at 12:36 PM.
11-02-2010, 01:39 PM   #33
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I was wondering today if it was possible to bastardise a TC to make it into TS contraption. Anyone ever tried that?
11-03-2010, 11:24 AM   #34
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QuoteOriginally posted by Nass Quote
I was wondering today if it was possible to bastardise a TC to make it into TS contraption. Anyone ever tried that?
What are "TC" & "TS" contraptions? I guess maybe TS = tilt shift? Maybe TC is teleconverter?

Dave

11-04-2010, 05:10 AM   #35
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Hello,

Yes, a teleconverter. Someone mechanically skilled with an engineering workshop might be able to take apart a TC and replace that default fixed outer housing with something jointed that might allow a bit of shift and tilt maybe? Of course it'd still be a teleconverted image (unless you also took out the glass prepared to lose infinity focus?).

Just curious, as a quick aside, would you happen to know of the formula to calculate which focus areas you 'lose' (ie closest focusable point becomes 100m away so you lose >100m) when you move a lens forward by X? And how would hyperfocality affect this? Ie grabbing made up figures out of thin air, say you had a 10mm lens, extended it forward by 2 cm so the furthest point of focus becomes 20m, but you also had it set at f16 (so you had a wide depth of field), does/would the hyperfocal area stretch beyond this new 'infinity focus point' point thus actually lessening the impact of the new infinity focus point? (ie although it shouldn't be focusable according to the new infinity point, because it's in the hyperfocal area it's still sharp)?
11-04-2010, 06:16 AM   #36
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A reverse mount macro adapter would give you a mount ring for the camera end. If you are using a PK-mount lens, an ElCheapo extension tube would give you a similar part and also a ring on which the lens can be mounted. These are threaded which could be a benefit. Both can be had for cheap from Ebay at least.

A related half-baked idea would be making the tubing out of two rubber lens hoods by maybe cutting them and using rubber cement for the seam. These might then be fixed to the mount / lens rings using extension narrow extension rings, provided that the threads match. With the extension tube set you'd get one extension ring that might be narrow enough for the purpose.

I don't have any experience of doing this myself, just trying to give you some idea(s) for cheap parts that might be of use in your project.
11-04-2010, 10:26 AM   #37
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QuoteOriginally posted by Nass Quote
Hello,

Yes, a teleconverter. Someone mechanically skilled with an engineering workshop might be able to take apart a TC and replace that default fixed outer housing with something jointed that might allow a bit of shift and tilt maybe? Of course it'd still be a teleconverted image (unless you also took out the glass prepared to lose infinity focus?).
That'd be possible, but I think there are easier, more effective ways to DIY.

QuoteQuote:
Just curious, as a quick aside, would you happen to know of the formula to calculate which focus areas you 'lose' (ie closest focusable point becomes 100m away so you lose >100m) when you move a lens forward by X?
As a lens of focal length F is moved a distance x from its infinity position (infinity position is one focal length from the image plane) the focus distance becomes:

Focus_distance= F(1+F/x)

Say you move a 50mm lens 10mm away from its infinity position. Its focus distance is:

Focus_distance= 50(1+50/10)=300mm [i]ie. things 300mm in front of the lens are in focus.


QuoteQuote:
And how would hyperfocality affect this? Ie grabbing made up figures out of thin air, say you had a 10mm lens, extended it forward by 2 cm so the furthest point of focus becomes 20m, but you also had it set at f16 (so you had a wide depth of field), does/would the hyperfocal area stretch beyond this new 'infinity focus point' point thus actually lessening the impact of the new infinity focus point? (ie although it shouldn't be focusable according to the new infinity point, because it's in the hyperfocal area it's still sharp)?
That'll take some algebra to get a useful answer but I'm sure the effect will be very small for the high magnification suggested by your numbers.

Keep in mind the "new infinity focus point" is simply where the lens happens to be in focus; move it a little more and the same formula applies. The in-focus regions in front of and behind the plane of focus remain those predicted by the DoF formulas.

There is always an in-focus range behind the subject (ie plane of focus) but it is very small if the plane of focus is far in front of the hyperfocal distance.

Dave

Last edited by newarts; 11-04-2010 at 02:52 PM.
11-04-2010, 03:33 PM   #38
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I would do it the following (rather destructive) way:

Get a dirt cheap K mount lens where the rear element moves when focusing, that has about 25mm space between bayonet flange and focus ring on the outside, and at least about 15mm free depth inside the lens before the focus assembly starts.

Then using a dremel tool or saw cut out a 5mm ring between flange and focus ring. sand edges clean.
(remember to really clean the lens afterwards!)

This will wreck the aperture ring, but hey, it ws a dirt cheap lens right?

Then using a thin rubber sheet (like bicycle inner tube) and some glue reattach the two pieces, making sure length of the lens doesn't get bigger then original.

If you need to fixate the tilt for video i would attach 4 steel strips on cardinal points between the two parts with hoseclamps, really tighten the bayonet side, leave the other side o bit loose to allow adjustments.

11-04-2010, 04:19 PM   #39
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I've tried a few diy approaches to make a tilt lens. The difficulty with most schemes is finding a means to solidly, precisely and repetitively position the lens.

So far the best low cost scheme for a bendable lens tube I've found is to use the ends from inexpensive extension tubes to attach to the lens and camera. A bendable corrugated rubber tube cut from a motorcycle shock absorber protector (BSA '69) was used between the tube ends, but any bellows tube about the right diameter can be used.

A $30, 100mm focal length enlarger lens will work well at the lens end of a 57mm tube. Other lenses can be used of course and enlarger lenses are inexpensive; The overall tube length should be a little more than the enlarger lens focal length minus 45.5mm (the distance between the camera mount and sensor).

An adjustable, repeatable location and tilting positioning arm can be made by pivoting an arm from the female tripod mount socket on the bottom of the camera - pivoting the lens about this point is the correct thing to do so far as tilt lens optics are concerned. An inexpensive $20 focusing rail makes a good variable length (for focusing) lockable pivot arm to position the lens. 2 Way Macro Focusing Rail Slider fr Canon Nikon Pentax - eBay (item 180333924982 end time Nov-24-10 08:03:12 PST)

Such a setup can work pretty well, but I don't recommend building one. You'll likely find it difficult to adjust precisely and you won't be happy with only one axis of tilt.

Consider spending about $125 for a Russian tilt adapter Hartblei Tilt Adapter for Pentacon Six Lens - Pentax - eBay (item 170548600701 end time Dec-02-10 21:14:31 PST) and a $85 Pentacon 6 (Kiev 60, Kiev 88) I32 wide angle lens MIR-38V kiev-88 saluyt camera - eBay (item 330485887179 end time Nov-16-10 09:58:32 PST) A $7 M42/K adapter is also needed - remove the spring: M42 Lens to PK Adapter for Pentax K10D K20D Km K7 - eBay (item 260687611760 end time Dec-04-10 07:44:40 PST)

I have the above set-up and it works well.

Dave

Last edited by newarts; 11-04-2010 at 04:29 PM.
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