Characterising an unknown lens through laser ray tracing

In the last few posts I've described how one can characterise any lens, by estimating its cardinal points through laser ray tracing. In this post I'll give a real world example of how and why I do it.

As a photographer who likes using old medium format film lenses and sensor bracketing, to create XPan, negative size equivalent, digital captures, I make use of Mamiya 645 lenses, in my case: 35mm, 45mm, 80mm and 150mm. The PhotonsToPhotos Optical Hub does not hold any information on Mamiya 645 lenses.

My favourite lens is the 45mm 645 Mamiya, which, using various adapters, allows me to capture a flat stitched digital negative as if taken with a camera with a 86x36mm sensor. From which I can crop a digital XPan equivalent 617 format image.

The first step is to put the lens at infinity and measure the focal length using extension tubes, which in this case came out at 45.9mm.

I also estimated the minimum focus distance of the lens from the sensor plane, ie  433mm.

I then took an image of the exit and entrance pupils and estimated a pupil magnification of 1.67.

The final measurement was to estimate the on axis entrance pupil position, relative to the rear flange surface of the lens, using the laser leveller technique:

From the above we can estimate this as 72mm. To this we need to add the Mamiya 645 focal flange distance of 63.3mm. Resulting in the on axis entrance pupil being located some 135mm from the sensor plane.

Knowing this location means we know the no-parallax point of the lens, focused at infinity, relative to the sensor plane.

From all the information I then used the PTP Thick Lens Hub to create the following model of the lens:

We also know that the hyperfocal distance is measured from the entrance pupil, so we can now characterise the depth of field scale on the lens by using a simple hyperfocal bracketing model, see here, by counting the number of rotations, ie images needed to cover from the hyperfocal down to the minimum focus distance:

The above also shows the infinity focusing zone, between H and mH, where we can dial in the any optical blur we wish at infinity, by taking an addition focus bracket, with the ‘best’ additional one being at or close to ‘infinity’. For landscape photography on a full frame camera, focusing at, say, 10 times H, is practically infinity, ie a 30/10 = 3 micron blur, if using a CoC of 30 microns. This is typically around the size of a single photosite. Thus showing, for a wide angle lens, say 15mm, shooting at f/10 and using a quality CoC of 15 microns, the (rule of ten) hyperfocal is at some 1.5m and thus ‘practical infinity’ is only 15m away, ie giving an infinity blur of 1.5 microns.

Using the above leads to the following focus bracketing model:

Which in turn leads to the following simple equation we can use to help characterise any depth of field scale, or create a new one based on a stated CoC:

We can now set x to the minimum focus distance from the entrance pupil, ie 433 - 135 = 298 mm in this case; H is the hyperfocal distance as measured from the entrance pupil, ie (f*f)/(N*c) + f; and n is the number of focus bracketed images we need to take from the hyperfocal to the minimum focus distance, at a given aperture (N). The above then allows us to estimate the circle of confusion baked into the depth of field scale from: (f*f)/(N*(x*(2*n-1)-f).

In this case, at f/22, by rotating the lens, I did a quick estimate of the number of focus brackets (n) at 3.6, using masking tape attached to the lens: 

Using masking tape and our simple equation also allows us to create any depth of field scale we desire, ie at any CoC we decide to use for focus bracketing. Plus we can add in the focus points, as we focus down from the hyperfocal, (green dots) on the above:

The above, DIY, depth of field scale has everything we need for landscape photography. We know where the CoC defined hyperfocal is located, ie the first green dot on the right; we know where to focus bracket down from infinity, ie at H, H/3, H/5 etc; and finally we know our infinity focusing zone at the CoC we decided to use for focus bracketing, ie between the first green dot, at the focus bracketing H, and infinity.

Feeding in all the data results in a CoC used for the Mamiya 645 45mm depth of field scale, using a focal length of 45.9mm, at some 53 microns. Using the quoted focal length of 45mm, I would get a CoC of 51 microns. These numbers may be compared to using the 'standard' full frame 30 microns CoC at the Mamiya 645 nominal crop factor value of 0.62. ie just over 48 microns.

As for using this information in the field, using the Rule of Ten (see link on the right), the hyperfocal distance at 45mm focal length is some 4.5m at f/10 and at a CoC of 45 microns. Thus at, say, a CoC of 15 microns, the hyperfocal is some 4.5*3, ie say 15m away. If I see there is a point of focus in the scene at, say, 5m away, I know I need to insert a focus bracket at about H/3, giving me a near depth of field at that focus of H/4, ie covering my 5m point of interest. But I also know the DoF scale uses a CoC of some 50 microns, which will likely create a focus gap if I use the f/10 DoF marks, thus I'll likely use the f/5.6 marks. As I say, all pragmatic and all calculable in my head.

Bottom line: I hope this post has been useful to others, but, as always, I wrote it for my own record, but freely share it. 

As usual I welcome any comments on this post or any of my posts. 

 

 

Laser Ray Tracing: Benchmarking

In the last post I outlined the basic approach to using a laser line leveller to help identify the cardinal points of an unknown lens. The basic workflow being:

1. Set your lens to the required focus, ie magnification, and, for a zoom, the required focal length;
2. Using extension tubes measure the focal length (F) and note the magnification (m). For example, at infinity m = 0. You can also accept a quoted focal length;
3. Take two in focus images of the aperture, one of the entrance pupil and one of the exit pupil. Calculate the pupil magnification (p);
4. Align a ruler along the axis of the lens, ideally at/near the centre line of the lens; 
5. Using a laser leveler (ideally two if you have them), take images of two laser lines that point to (near) the (on axis) entrance pupil and the rear flange surface of the lens. Try and position the lens rear flange over the centre of the camera, eg iPhone, taking the picture;
6. Ingest the images into (say) Photoshop and rotate all the layers so the lens axis is horizontal (convention dictates the exit of the lens is on the right;
7. Using Photoshop guidelines and the line tool, identify the position of the on axis entrance pupil and the flange surface;
8. Using the ruler locate the sensor location, ie for a Canon EOS lens, 44mm from the lens flange surface;
9. Measure the distance from the sensor to the entrance pupil (k) and use the following expression to estimate the lens hiatus or internodal distance (I): k - 2*F + F*(1/p - m);
10. Using the PhotonsToPhotos  Thick Lens Optical Bench, enter F, m, p, I and the infinity aperture (N) of interest into the calculator.

In order to show the workflow, in this post I'll look at my Canon 24-105mm F4 IS USM lens and set it to 24mm infinity focus, to compare it to the lens in the PTP database.

In the first image above we see the optical axis (red) ray in the top image, together with a ray helping to estimate the location of the (on axis) entrance pupil. In the second image we see two arbitrary rays helping to locate the lens rear flange surface. The third image is a composite view.

The final step is to add a few Photoshop guides, and using the line tool, trace out the laser rays to identify the on axis entrance pupil, the lens rear flange, and, finally, the sensor, ie, in this case 44mm from the lens rear flange surface:

From the above we can estimate the entrance pupil is 76mm from the lens flange, which leads to the entrance pupil being 76+44 = 120mm from the sensor; giving us k.

From the images taken of the pupils, the pupil magnification is about 4.2. As I set the lens to 24mm focal length for this test, and as I wish to compare with the PTP data base, in this case I chose to use the PTP focal length of 24.93mm. This leads to a calculated internodal of 76.1mm.

Putting all the information into the PTO Thick Lens Optical Bench results in the following:

Which can be favorably compared to the PTP Optical Bench:

So, there you have it, in about 15mins you can map out any lens, simply using a DIY laser leveller and a few iPhone images.

As usual I welcome any comments on this posts or any of my posts. 

 

Create your own lens model through laser ray tracing

This is a slight edit of the original post.

In this post I will show how anyone can create a 'thick lens model' of any lens.

Of course, the first question to answer is: why bother?

Do I really need a lens model to be a better photographer?

For instance, as a single shot macro photographer, you don't really need to know anything about the lens you're using, ie all you need to do is focus on the subject and capture an image, knowing that closing down the aperture will give you more 'depth of field' coverage, but at the cost of introducing diffraction blur.

If undertaking macro stacking, all you really need to know is the focal length and the magnifications. From this you can use wave optics to estimate the depth of field to inform the step size, ie the total visible band DoF being  (0.00055*4*(F*(1+M/p))^2)/M^2. With p and M being easily estimated by simple measurements.

If you are a 'rotating' pano shooter, who wishes to minimise post processing stitching issues, you will want to position your lens entrance pupil over the point of rotation. But you can do this easily by adjusting the camera-lens position on a nodal rail, by looking at the misalignment between a close and far object.

As a landscape photographer you may wish to know the hyperfocal distance, and this can be estimated from (F*F)/(N*c), where F is the focal length, N the aperture and c the circle of confusion value you have decided to adopt. But, of course, any sensible landscape photographer will focus beyond the hyperfocal. That is magnification can be ignored, and the position of the entrance pupil (from where the hyperfocal is measured) is a near irrelevance in the field, eg using the sensor position (marked on the camera body) is good enough. Some, like me, will simply use the 'Rule of Ten' to estimate the hyperfocal in their head (see the link on the right), and set focus accordingly. 

Therefore, the answer is: no, you don't really need a lens model.

But for those that still wish to have a lens model that is 'better' than using a thin lens model, ie assuming all the lens cardinal points sit a focal length from the sensor, the following shows you how to create a thick lens model at home, with equipment you likely already have.

Before looking at an outline of the process, the simplest and by far the best approach is to go to Bill Claff's excellent site (PhotonsToPhotos) and look to see if your lens is registered on his Optical Bench Hub. As a minimum, if your lens is in his data base, it will give you an ‘accurate’ (infinity focused) lens model at the focal length extremes for a zoom lens, or sometimes at intermediate zooms, (or at a single focal length for prime lens); and for some prime lenses you may also be lucky that Bill has been able to construct a focus model as well.

But if your lens is not in the PTP database, or you have a multi lens set up, ie a lens and, say, an optical extender or reducer coupled together, then you will be out of luck. In this case, the following procedure may be of interest to you.

One caveat to note is that this procedure works 'best' for 'rectilinear lenses, eg not fish eye lenses. As usual, I’m using the following thick lens model:

Establishing the Focal Length 

As a worst case, we will assume you don't know the lens infinity focal length. In this case, one simple way to estimate this is to use a macro tube extender (generally you should use two extenders if you are not at infinity focus), see here for more information  eg:

• Measure the extension tube, attach the extension tube between the camera body and the lens. Ensure the lens focus ring is turned all the way to the infinity symbol (if you are trying to model a lens at some other focus or magnification you will need to refine the procedure).
• Place a ruler in front of the lens. Move the camera (or the ruler) back and forth until the markings on the ruler are perfectly in focus.
• Once in focus, look through the viewfinder or use "Live View" to see how many millimeters of the physical ruler fill the width of your image. Or capture an image and evaluate in post.
• Estimate the focal length from (L*x)/S, where L is the extension length in (say) mm, x the length of the ruler visible in the image, and S the size of the sensor, eg 36mm for a full frame. 

Alternatively, accept the manufacturers infinity value. But note, at focus distances less than infinity, the focal length can change, especially for a macro lens.  

Using laser line ray tracing

All we need to do, to construct a first order thick lens model, is to locate the entrance pupil on the optical axis (we can not use the laser line technique to locate the exit pupil on axis location, this needs to be calculated), measure the pupil magnification, measure the focal length, and locate the sensor location from knowing the flange position of the lens and looking up the manufacturer’s published flange focal distance.

There are several ways to locate the entrance pupil, eg using the pano rotation approach or with a laser leveller as in this post . As for the pupil magnification, we simply estimate this by, say, taking an image of the exit pupil diameter and divide this by the entrance pupil diameter.

Assuming we are assessing the lens at infinity, first, set the lens focus to infinity, and, for a zoom, the focal length you wish to model. Then measure the focal kength.

My advice is to set up a camera over the scene and take images of all tne laser lines, for assessment in, say, photoshop. I use an iPhone and mark all the rays on a composite image in photoshop. It is also essential that you place a ruler next to lens, for scaling, and ideally positioned at the optical axis to remove parallax errors.

The first step is to establish the optical axis of the lens. This can be readily achieved by aligning the lens and laser leveller (using the laser cross lines) until the projection of the laser through the lens aligns with the laser lines that do not go through the lens. As can be seen, I also make use of a simple white surface to help with this step, and take an image

The important thing now is to NOT touch the lens.

We now use the laser leveller at an angle to the optical axis, and shine it through the front of the lens, and adjust it so that the projected laser line is symmetrical in the projection. This laser line is a reasonable estimate of the on axis entrance pupil location. Take another image. The image below shows the general set up, ie not from the camera positioned above the lens:

We now need to mark the position of the rear flange surface. I find the best, non contact, method, is to use two laser levellers to locate the flange surface and take another image. An alternative, if you only have one laser leveller, is to establish two laser lines by selecting a feature on the flange to aim at, eg a screw. Knowing the position of the lens flange surface allows us to add in the flange focal distance, to locate the sensor location. 

We then use Photoshop to help us trace out the laser lines and estimate the distance between the entrance pupil location and the lens flange position.

Knowing the focal length and using laser line, physical ray tracing, we have now captured all the information we need, ie the entrance pupil location on the optical axis, and the location of the sensor, allowing us to calculate the position of the entrance pupil, relative to the sensor (k). Plus we know the pupil magnification (p) and the focal length (F).

Putting it all together

The final step is to make use of Bill Claff's Thick Lens Optical Bench (TLOB):

However, before we can use the TLOB, we need to work out the internodal distance (I). Which is easy to do from the measurements we have made, ie I = k - 2*F + F(1/p - m). Noting this can be negative. Note k will need to be measured/recalculated for each (non zero) m, as we don’t know how the entrance pupil moves relative to the sensor.

All we need to do then is enter the following information into the TLOB:

• Focal length (accepted or measured)
• Pupil Magnification (calculated from taking a picture of the pupils)
• Internodal distance (calculated from the measurements we took)
• N the aperture of interest 
• Focus distance or magnification of interest if mapping a lens not at infinity

The PhotonToPhotos Thick Lens Optical Bench will then give us a model of our lens. Will it be perfect? No, as the measurement accuracy we can achieve will limit things. Will it be a better model than using a thin lens model? YES!

Will it be fun and interesting to do? Once again YES!

As this has been a rather long post, I'll bring it to a conclusion, and follow it up with posts that illustrate the technique in action.

As usual I welcome any comments on this post or any of my posts. 

Geting to know your lens: The Ultra Digital XPan

In the last post I covered my 'final' experiment in creating a Digital Multi-Format Shift Camera set up, that covers XPan like sensor capture (over 65x24mm sensor equivalence)  and Medium Format sensor capture (for example a 78x44mm sensor equivalence).

In this post I will show how one can get an optical model of this system, simply by knowing a few, easily obtained, dimensions; eg the entrance pupil location on axis, the camera body's flange focal distance, the pupil magnification, and the focal length.

In this post I will look at my Canon R, coupled to the Laowa EF to RF Magic Shift Converter, coupled to the Kipon 645 to EF shift adapter, coupled to my 45mm Mamiya 645 lens, set at infinity focus.

The location of the on axis entrance pupil location of this three sub-system lens system can be estimated using my laser leveller method (see this post here). 

The set up is simplicity itself and estimating the position of the on axis entrance pupil takes a minute or so. The set up is to place the lens or lens system in this case, horizontally on a sheet of paper on a flat surface.The first step is to set up a suitable rear surface to help us adjust the laser angle, ie the cardboard box in this image. Then we use the laser leveller to establish and mark a zero from which we will measure the position of the entrance pupil location, in this case the front edge of the lens, which we will use as our reference plane. We could have also used the lens rear flange:

Having established a reference, we now simply use the laser leveller to record two rays that will allow us to locate the entrance pupil. It is good practice to not move the laser too far from the optical axis, due to potential pupil curvature:

As can be seen, one does not need to worry about focus on the rear surface, as all we are looking for is for the laser to be centred in the projection. With these three lines, we now have an estimate of the location of the on axis entrance pupil, in this case 36mm, from the front edge of the lens body:

Next we measure from the front reference edge of the Mamiya lens to the flange surface that will abut with the camera, ie the one for the rear shift Magic Shift Converter (MSC). In this case I estimated it at 138mm, and I called the overall lens diameter 75mm. That is all the lens complexity is represented by a black box model, 138mm long, 75mm in diameter, with an entrance pupil at 36mm from the front of the black box.

The next task is to estimate the pupil magnification of the lens system, which is easily done by inspecting the front and rear of the lens system. In this case, my eyeball approach told me the pupil magnification was near unity, ie the lens system was neither retro focus of telescopic in nature. That is, the MSC’s influence on the Mamiya 645 45mm, is to convert the pupil magnification from 1.6, ie a retro focus lens, to unity.

Also, although I'm using a 45mm Mamiya 645 lens, because of the MSC this becomes a 45x1.4 lens, ie a 63mm focal length lens system. From the lens depth of field scale, and the manufacturer's data, the minimum focus distance is 450mm (which I took as read).

The Canon RF system's flange focal distance is 20m, which allows us to estimate the position of the entrance pupil, relative to the sensor plane, ie 122mm.

As for the sensor, I simply used the 35mm diagonal, ie around 43.3mm, but I could also enter any of the stitched sensor dimensions, ie to estimate the angle of the field of view.

The final stage was to input all the measurements into the Poor Man's Optical Bench (see here) and focus at 'infinity', ie 60m away. Giving the following output:

 

The above providing us with some useful information, eg an estimate of the location of the no parallax point, ie the on axis entrance pupil location and from where the hyperfocal distance is referenced eg as shown below:

Bottom line: although we can tap into the PhotonsToPhotos Optical Bench, thanks to Bill Claff’s great work, in some cases our camera/lens set up can't be realised through PTPOB. In such cases, this post has shown how one can get an estimate of the main camera/lens characteristics. Surely a better approach than using a thin lens model. 

As usual I welcome any comments on this post or any of my posts.

 

 

 

 

 

Ultra 'Digital XPan' Image Quality and Multi-Format thoughts

In the last two posts I discussed my Ultra Digital XPan set up: using a Canon RF camera, a visible band R and an IR converted RP in my case, combined with Mamiya 645 film primes (35mm, 45mm, 80mm and 150mm), coupled together via two shift adapters - one of them with optics that result in a stop increase in focal length and aperture.

As photographers we are conditioned mainly through our available technology. For example the lens focal lengths and the sensor aspect ratio and size. which lead us to seeing the world through the system's 'field of view'.

For full frame cameras we 'see' through a 3:2 aspect ratio (AR) sensor. Whereas micro four thirds and digital medium format shooters usually see through a 4:3 AR.

As I evolved my Ultra Digital XPan I also saw it as an adaptable AR system. That is, not restricted to a 65:24 XPan AR.

Let's take the standard full frame sensor of 36x24mm as our baseline 3:2 AR and compare this to one of the best medium format camera systems, ie the Phase One IQ family. The Phase One sensor size being 53.4x40mm:

If we now add in the Ultra Digital XPan (flat stitched) sensor equivalent sizes, after using both adapters together, we see the following comparison:

One of the 'advantages' the Ultra Digital XPan set up is that we can rotate the camera (landscape/horizontal or portrait/vertical orientation) and independently rotate each adapter, giving the system multiple 'degrees of freedom'. We can also replace the Magic Shift Converter's optics with a 'simple' pass through adapter. Or, for example, we could 'just' use the MSC on its own, giving a 56x24mm or a 44x36mm stitched sensor equivalence.

As a final illustration of the sensor size adaptability of the set up, if we use the front shift in landscape mode of 30mm, which gets enlarged by the MSC by 1.4, and use the MSC's shift of 20mm in portrait mode, we arrive at a 78x44mm sensor equivalence, which, when compared to 35mm full frame and the medium format Phase One, looks like this:

To illustrate this 78x44 option, here is a (scaled for display) test image, taken with my 45mm Mamiya at 45x1.4mm because of the MSC, giving a 14903x8124 stitched image in Lightroom, ie some 135MP image:

Of course all the above adaptability must come at some cost.

I will ignore the obvious cost of buying the two adapters and a set of medium format lenses. A more important çost for many photographers will be the impact on Image Quality, but this is where it gets a bit subjective.

If you are a pin hole film shooter, your definition of IQ will be different to someone shooting with a Phase One IQ4 system. Thus I lean towards IQ being in the eye of the beholder. If it works for you, then all is right with the world :-)

After a very helpful exchange on the S&T DPReview forum (many thanks to those that chimed in) I decided to approach IQ in a very pragmatic way.

First, I decided to not 'worry' about resolution, as I can't change this, ie I'm stuck with using the Mamiya 645 film primes and the optics in the Magic Shift Converter. This decision allowed me to not get diverted by creating MTFs and using MTFMapper etc.

But I still wanted a 'feel' for how 'good' my set up was: so I elected to use a 'field map' approach:

• Set the aperture fully open
• Point the camera down at a flat surface with texture, eg a carpet (see set up image below)
• Place a reference object in the middle of the frame, to aid stitching. I used a ruler
• Set exposure and focus
• Capture your images for assessment
• Stitch if evaluating a pano frame
• Use the find edges filter in Photoshop to visualise the ‘IQ' across the image

The set up looked like this:

The RAW capture from one of centre pano captures looked like this:

After stitching, in this case using the full shift of both adapters with my 45mm Mamiya 645 lens at f/8, the resultant, Lightroom, (perspective) stitched capture (21216x4741) looks like this:
 

After applying the find edges filter I got this:

The stitched image in portrait mode, ie 86x36mm, looks like this:

On inspection, I am pretty content with what I'm seeing in both images. Of course there is some 'fall off' towards the edges, especially in the extreme case. But the overall linearity and ‘IQ', to me, looks OK.

As usual I would welcome any comments on this post, or any of my posts.

Ultra Digital XPan - Part 2

In the last post I introduced my 'Ultra Digital XPan' set up, which looks like this in portrait mode:

 

Using my geared head, on a good tripod, gives me solid positional control over composition. To complement the internal levelling guide in my Canon R, I've added a three axis cold shoe bubble level. Finally, I use my H&Y Revoring filter holder, to handle my 82mm filters, thus allowing me to add front filters, for example, on my 720nm IR converted RP I can add a 830nm cut filter.

As mentioned in the previous post, using dual shifts, in conjunction with the Magic Shift Converter optics, I can realise shifts of some 62mm, ie over 30mm in each direction.This allows me, as shown in the last post, to create 4:1 near parallax free captures. I say near, as the lens does move relative to the camera on one of the adapters. 

The resultant stitched image being equivalent to a single image being taken with a sensor that is 98mm x 24mm.

In this post I will discuss using the set up, in the field, in 'true' XPan aspect ratio mode; that is seeking to maximise the pixel capture. 

To achieve this, as shown in the picture above, the camera is placed in portrait capture orientation, to ensure a 36mm sensor height, compared to an XPan negative of some 24mm.

As I was feeling lazy, the test subject is a view 50m from my house. I was using my Canon R and my 80mm Mamiya 645 lens.

Having explored the exposure extremes with my camera's histogram, ie shifting across the full shift range, setting focus and aperature (f/11 in this case), I took a seven image pano bracket set that looks like this:

The two extreme captures represent the 10mm shifting using the Magic Shift Converter, whilst the other captures cover the physical 30mm shift of the Kipon 645 to EF shift adapter, with the MSC at zero. The Kipon shift then ends up as 30*1.4 mm after passing through the MSC adapter’s optics.

After preprocessing in Lightroom, using DXO  PureRaw 5 in this case, I processed the pano bracket set using Lightroom’s Photo Merge, using Perspective projection.

This resulted in a 16165x6782 image, equivalent to a 86x36mm sensor, ie larger than a classic film XPan negative, of 65x24mm.

After cropping the image to an XPan format (65:24), the final, digitally mounted, image looks like this (greatly scaled here because of its size):

To give a feel for the details, here is a 1:1 screen capture of a part of the image:

As far as I'm concerned the experiment has been a great success and I'm content I've got a usable digital XPan-like set up, albeit using medium format Mamiya film lenses and sensor bracketing.

As usual I would welcome any comments on the above or any of my posts. 

 

Ultra Digital XPan - Part 1

If you have been following this blog, you will know I like to ‘play about' with adapters; especially those that allow me to capture images for perfect flat stitching in post.

In previous posts, for example here, I have discussed the Laowa Magic Shift Converter and illustrated its potential when coupled to a Canon TSE 24mm Tilt/Shift lens.

In this post I'll discuss a more flexible arrangement, that allows different focal lengths to be used.

The lenses I've explored are from the Mamiya 645 family, ie 35mm, 45mm, 80mm and 150mm. Although I've dropped using the 35mm as, unfortunately, I seem to have a bad copy, with one side of the image rather distorted, compared to the other side.

In this test I used the 45mm Mamiya 645 lens.

The  camera set up I used loks like this:

That is: a Canon R, coupled to the Laowa EF to RF Magic Shift Converter, coupled to the Kipon 645 to EF shift adapter, coupled to my 45mm Mamiya 645 lens. With this arrangement my total shift is of the order of 50mm, ie 25mm in each direction.

Of course the MSC transforms the 45mm focal length into about a 63mm lens.

Having set up the composition, checked the exposure over the shift range, set focus and aperature (f/11 in this test), it was a simple matter to capture 5 images:

• Kipon +15mm + MSC 10mm
• Kipon + 15mm + MSC 0mm
• Kipon 0mm + MSC 0mm
• Kipon -15mm - MSC 0mm
• Kipon -15mm -  MSC 10mm

Once captured, the five images were processed and Pano mergered in Lightroom. The resultant (flat stitched) pano was 18636 x 4664, ie just short of 87 mega pixels.

This is achievable because of the optics in the MSC, which expands the Kipon’s 30mm physical maximum shift by 1.4.

At the Canon R's pixel pitch of 5.34 microns, this is like using a camera with nearly a 100mm x 24.9mm sensor, ie 36 + 30*1.4 + 20. Graphically looking like the comparison below: where the red rectangle represents a normal full frame sensor, and the blue the 'Ultra Digital Xpan' created with the above set up.

As for the test image, it looks like this (scaled to display in the blog). The 35mm full frame, horizontal, field of view equivalent is similar to a 23mm focal length:

So, I think, finally, I've found my ideal digital XPan set up. If I want to create an ultra wide, 4:1, flat stitched, pano I can use the MSC with the Kipon shift adapter, converting my Mamiya lenses into a 49mm, 63mm, 112mm, 210mm set . If I only want to emulate an XPan aspect ratio, I would replace the MSC with a simple EOS to R adapter (which I have), allowing me to shoot at 45mm, 80mm and 150mm (as my 35mm is not really useable). Finally, with the MSC arrangement I could also shift in two directions using the Kipon and MSC in combination, ie to create various medium format equivalent aspect ratios.

As usual I welcome any comments on this post or any of my posts.