Double Adaption: for ultimate control in creating a ‘digital XPan’

Those that have been following my recent posts will know that I've been experimenting with sensor bracketing, and, in particular, the 'best' way to simulate a digital XPan, using one of my Canon RF or EF-M cameras (either visible or IR) and various adapters, eg see the Fotodiox site for examples of the many adapters you can get.

In this post I'll be looking at the benifits of double adaption. That is using more that one adapter.

As discussed previously, using Mamiya 645 lenses, with a larger image circle than the Canon RF format, allows one to exploit shift, and one might be tempted to opt for a single adapter, such as the Fotodiox Mamiya 645 (M645) to Canon RF Shift Adapter:

This adapter allows some 30mm of shifting (+/- 15mm); which initially looks great, until you factor in the Mamiya lenses.

As an example, lets look at the 35mm Mamiya - Sekor C f/3.5 N that I have (#107008):

Like all/most Mamiya 645 lenses, the infinity is at a hard, mechanical, stop, and my experience is that infinity can be slightly thrown out when coupled with adapters. In theory one could try and adjust the lens for a more accurate infinity with an adapter, however, this could end up as a wasted effort if you are using different adapters, as each adapter may be a few microns adrift from each other because of manufacturer’s design, quality control and tolerances.

This is where double adaption comes in.

The first adaption is to introduce a shift adapter to go from a Mamiya 645 lens to a Canon EF mount, then add a focus correction adapter to go from EF to RF. The adapters I have used are the Kipon Shift M645 - EOS, and the Fotodiox dlx Stretch EF - EOS R.

 

As can be seen, the additional advantage of using the EF - RF stretch is that it comes with rear, drop in, magnetic ND filters (ND4, 8 and 16). The final double adapter set up looking like this:

Using this arrangement of adapters allows me to capture a 61.75 x 24 mm, stitched, flat, panorama, using my visible band R or my IR (720nm) converted RP. That is creating a digital XPan image, albeit by using a medium format Mamiya film lens, rather than an XPan film lens. 

The in field workflow I've come up with goes like this:

• Set the Mamiya on its widest aperture, eg f/3.5 for my 35mm lens;
• Calibrate the lens for infinity by putting the lens at infinity, zooming in to the farthest point of interest in the image and adjusting for maximum focus at that point, using the stretch adapter;
• Set the required aperture (I tend to use f/16 or f/22 for maximum depth of field, and correct for diffraction softening in post) on the lens and the exposure time, using the histogram and ETTRing;
• Ensure the ETTR exposure covers the shift extremes;
• To ensure maximun pano blending success, I personally take three images, ie at the two extremes (+/- 15mm) and one in the middle with zero shift.

As for post processing I find the following workflow creates what I'm looking for:

• Ingest into Lightroom;
• Use Raw Detail to clean up the images;
• Use pano photo merge;
• Use Topaz AI, including, if required, dust and stratch (although this is now available in Photoshop ACR and hopefully will be in Lightroom soon) and Topaz Superfocus, to tidy up any diffraction softening;
• Tone and finish as required.

The following test shot was taken with the 35mm Mamiya at f/22, and I've zoomed in to show the detail that I obtained. The Image was taken with my IR converted RP and the final image is 10772 x 4217, ie 61.7mm x 24.2mm, and left in RGB space:

The bottom image above is a screen grab from a 1:1 zoom, to illustrate the details.

For completeness here is the B&W version, which I prefer, as colour integrity can be a challenge when post processing IR captures in colour:

I'll wrap up this post at this point as I think I've covered everything I wished to discuss. The bottom line being that double adaption is a viable way to ensure infinity focus on a manual MF lens when sensor bracketing. For me, knowing I can simulate an XPan with my mirrorless digital camera is fun and, I hope, will turn out to be worth while.

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

A New Lens for sensor bracketing

Keeping with the theme of sensor bracketing, I thought some may be interested in a new lens I've just got: a Laowa 15mm f/4.5 Zero-D Shift: link here 

As the name of the lens implies, this is a shift lens and is fully manual, ie there is no electronic coupling to the camera.

The shift direction is fully selectable and shifting is achieved by rotating a ring on the lens. The shift mechanism is rock solid and a joy to use. 

The amount of shift is +/- 11mm, thus, using my full frame Canon R or full frame IR converted RP, allowing the creation, in post, of an image as if it was captured by a 58mm x 24mm or, by shifting vertically, a 36mm x 46mm sensor.

For the greatest flexibility I decided to purchase the EF mount version, so I could couple this to my RF format cameras (or EF-M cameras) by one of the many EF to RF or EF-M adapters I have.

To show the pano capability, here is a test image taken with the visible band Canon R. In this example creating a 10285 x 4225 pixel image:

This second test is a non-shifted IR capture, cropped to a square format:

So far the experience with the lens is good. It is solidly built and appears to be of good quality, and the shift mechanism is a joy to use. The only 'downside' being the bulbous front lens, which I will need to be carefull with.

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

 

Another look at Sensor Bracketing: Part 3

In the last two posts (here and here) I discussed what I call 'sensor bracketing', that is exploiting a lens with a larger image circle, to allow moving the sensor relative the lens, without parallax or vingetting. In this way we can emulate larger sensor formats, say, like the Hasleblad XPan with it's 65x24 film size, via rectilinear pano merging in post.

Up until now, I've discussed exploiting my Canon 24mm Tilt/Shift lens, including the addition of extra shift via the Laowa Magic Shift adapter. 

In this post I'll be looking at how one can set up a digital 'XPan' using secondhand medium format lenses and manual shift adapters.

Let's first remind ourselves what the Hasselblad 65x24mm XPan film camera looks like, which is not manufactured any more, but remains expensive to buy on the secondhand market:

As for lenses, you can get three native primes for it, 30mm, 45mm and 90mm: shown below with the viewfinder that comes with the 30mm lens.

To emulate the above in a modern, full frame, digital, mirrorless camera, the Canon R or IR converted RP in my case, we need to first substitute out the XPan lenses. I decided to do this with Mamiya 645 lenses.However, the only Mamiya lens that matches the XPan’s primes is the Mamiya 45mm, I therefore needed to accept being 'close enough', by using the 35mm and 80mm Mamiya 645 lenses. Additionally, I also have a 150mm Mamiya 645 lens, which has no XPan equivalence.

To connect the Mamiya lenses to my Canon RF mount cameras, I decided on a Fotodiox shift adapter that has a foot, so that I can keep the lens stationary, allowing the camera to shift relative to a static 645 field of view. The adapter allows a +/- 15mm shift, ie 30mm, no parallax, total shift.

Pulling the above together with a few other gadgets, one version of the set up looks like this (note you don't need the pano rotator or the Canon R cage):

As for capturing two pano brackets, ie at + and -15mm, the biggest problem to address is the lack of a viewfinder. To overcome this, I make use of the Mark II Artist's Viewfinder, which you can download from here.

This iPhone App allows you to set up virtual cameras, so, in my case, I've set up a 35, 45, 80 and 150mm virtual XPan, with a 65mmx24mm sensor. This set up allows me to explore compositions and assure myself that the shifted frames will cover the scene of interest.

As an example, here is what the Artist's Viewfinder shows of a simple test scene:

Here we see all four lenses displayed within the digital XPan format, however, you can then zoom in on the focal length of interest  

As for the final image, here is an 80mm capture (with a field of view close to the XPan's native 90mm), taken by shifting the camera +/- 15mm.:

The merged image is 12020x4515 pixels in size, ie equivalent to an XPan's film size of 65x24mm.

So, there you have it, with the use of some secondhand 645 lenses and a cheap manual adapter, you can emulate different cameras: in this case an XPan.

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

Another look at Sensor Bracketing: Part 2

In the previous and first post in this short series about 'flat/planar sensor bracketing', I started with one of my best quality lenses: the Canon TSE II 24mm L.

The larger image circle of the TSE lens being exploitable in shift mode, to allow me to add an addition 24mm to the horizontal capture, thus creating a final, flat/planar, stitched image equivalent to using a sensor of 50x24mm. As was said before, not quite an XPan’s 65x24mm film size, but close. 

In this post I'll add in an additional piece of technology that will allow me to create sensor flat/planar bracketing out beyond the XPan, to some 84x24mm.

The technology I'm adding into the equation in this post is the Laowa Magic Shift Converter (MSC):

The MSC has +/- 10mm of shift, and sits between any Canon EF lens and the Canon R (in my case, ie there are other mount options) Thus, using the MSC, with its additional glass, means the 24mm TSE becomes a 33mm focal length TSE lens, with a field of view close to a 30mm XPan. The MSC also introduces one stop reduction in exposure. 

To explore the limitations of using the MSC with the TSE I restricted myself to looking at shifting both adapters in the same, horizontal, direction, ie I could also have used the TSE to Shift up and down, and the MSC to shift left and right, to create a Medium Format sensor equivalent format, eg [36+(24 or 20)] x [24+(20 or 24)].

In this pano experiment I continued to use the PocketPano frame, to keep the TSE lens stationary, ie only the sensor moved.

As usual, my test scene was my garden and I shifted both the TSE and MSC and accepted vignetting, to see how the software handled things:

After ingesting into Lightroom, I undertook a pano merge, using the perspective option, which generated the following 15830x4684 pano stitch (note, owing to the size of the images, the following are screen grabs):

 

Although I used my geared head and in-camera levelling feedback, clearly I wasn'y quite level.

After a bit of LR toning I ended up with the following image, which, at the Canon R pixel pitch and not being level, is 84.5x24mm equivalent, ie if I had cropped out the edges:

Finally, here is a comparison with a 617 (XPan) size, ie 65x24, showing the ability to adjust the scene in post, without losing the XPan size:

Clearly at the edges one can see the image quality falling away slightly, as you would expect at the edge of a lens; and this can be compared to rotational stitching where we maximise the use of the central region of the lens, albeit at the cost of geometric/transformational stitching/stretching.

So, what can we take away from this experiment with using the MSC adapter with the 24mm TSE?

First, modern stitching software is robust and seems to handle 'capture artefacts', such as vignetting, well, as long as you have sufficient image to image overlap.

Secondly, if you accept the 'cost' of sensor bracketing and stitching, eg ‘static’ scenes,  you can use single and multiple shift adapters to emulate the film area on an XPan and wider; albeit using a TSE lens.

Thirdly, if you 'only' use the MSC you can use any Canon EF lens with your Canon R (plus there are adapters for other combinations) and thus create a 56*24 mm pano, from two captures, ie 10mm left shifted and 10mm right shifted. However, you will observe vignetting, although this is less of an impact when using the 617 central crop. I’ll be writing about using the MSC with EF lenses in a future post.

Fourthly, using the TSE and the MSC orthogonally you can create a 3x3 capture to emulate a medium format sensor, eg [36+(24 or 20)] x [24+(20 or 24)].

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

Another look at Sensor Bracketing: Part 1

In the next few posts I'm going to take a 2025 look at, what I call, sensor bracketing; which, so there is no confusion, I define as planar shifting the sensor relative to a lens.

Clearly, you can not sensor shift on a camera with a non-shift lens that is designed for that camera's format, ie where the lens image circle is 'just' covering the sensor's surface.

Before looking at what I've done, let's look at one of the ultimate sensor bracketing cameras: the ALPA 12 XY camera, that allows 25mm shifting on the horizontal axis, as well as vertical shifting, coupled with a Rodenstock HR lens, with a 115mm image circle, and a Phase One IQ 150MP back:

The ALPA 12 XY is not made anymore and the cost with, say, a Phase One IQ back etc would make your eyes water! 

Although there are other Technical Camera based solutions, for mere mortals, you need to use a 'normal' camera with, say, a more affordable tilt-shift lens that matches your camera, or, via a shift adapter, use a lens from a camera system with a larger image circle. 

In my case the options  look like this:

• My 24mm TSE, coupled via an electronic adapter, to my Canon R camera, or, via an EF to EF-M adapter to one of my Canon EF-M cameras
  
• One of my Mamiya 645 lenses (I have three at 35mm, 45mm and 150mm), coupled to either my R or one of my Canon EF-M mount cameras (visible or IR converted) via one of more adapters that I have

In this post I'll start by exploring the 24mm TSE, tilt-shift, lens approach on my R camera:

For now I'm ignoring the tilt functionality, shown above, and restricting myself to the +/- 12mm shift, which means, for a full frame sensor of some 36x24mm, I can achieve a theoretical lens-centric, sensor bracketed image of some 60x24mm, ie a 5 by 2 pano (witout cropping into the image); not quite an XPan's 65x24mm image, but close.

This is achieved by exploiting the large image circle of the TSE lens, relative tho the standard 35mm image circle:

To provide a stable base for the set up, I used some technology I had laying around, ie a frame and nodal head from PocketPano, that locates the 24mm lens over the entrance pupil, giving the flexibility to carry out additional rotational captures if I wish to so do. The PicketPano, by design, also allows me to keep the lens stationary, that is the sensor shifts, relative to the lens. 

I then coupled the above to my Canon R, and added in two additional gadgets I had laying around: an inverted AcraTech ball head, to use as a levelling base, and a Siru L-10 Monopod Tilt Head, giving me the following arrangement:

The above giving me full control over how I wish to capture my images, ie via planar sensor bracketing alone, and with the addition of rotational pano captures if I wish. 

So let's look at some results from my garden. 

In the first test I followed a standard approach to pano bracketing, and took a central image and rotated both left and right to capture two additional images. I set the rotation clicks to 15 degrees, as this, together with the single image horizontal field of view, gave me a result close to the FoV of a 30mm XPan. 

After processing in Lightroom, I ended up with the following cylindrical projection merge, equivalent to a 44mm sensor (horizontally):

I chose cylindrical projection because I was only taking a single row of rotational pano images. If I had chosen to use perspective projection the above pano merge would look like this:
 

From the cylindrical projection, I cropped out a 5 by 2, rather than an XPan 617, image and post processed the following image in LR:

In the next test I captured two images, one shifted left by 12mm and one right by 12mm, ie no rotation at all, giving the following pano merge (untouched) in LR, but this time using the perspective projection, to achieve a 'flat' image - as you can see, I wasn’t perfectly level:

We can clearly see the advantage of using the sensor bracketing approach, ie keeping the lens stationary, thus allowing the use of perspective merging. After a bit of LR tiding up and cropping to a 5 by 2 format, I ended up with the following image:

Of course, in the end its all all about what look you wish to achieve.

I'll bring this post to a conclusion here, as I only wanted to introduce the subject of 'sensor bracketing'. In future posts I'll explore alternative and affordable ways to sensor bracket without a tilt-shift lens.

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

Poor Man's Optical Bench: Macro Update

Just a quick update on my Poor Man's Optical Bench simulator, that you can access from the right hand link.

In addition to a few UI tweaks, such as being able to show an outline of the lens and camera, after entering a few basic dimensions, I've added an extension tube simulation.

Once you have set up the non-extended lens (see previous posts), all you need to do is to add in the extension length you are using, and the simulator will give you an estimate of the new magnification.

Knowing this, you can then return to page 1 and click the link to Zerene Stacker's DoF calculator.

As the ZS site says: “the Zerene Stacker includes a unique macro/micro depth-of-field calculator that combines both diffraction blur and classic circle-of-confusion. 

Very briefly, the wave optics calculation is done by using the diffraction limited criterion of 1/4-lambda wavefront error. That allows the MTF curve to sag a little bit at worst defocus, but does not change the cutoff frequency. The classic calculation uses standard geometric optics, starting with a specified diameter for the allowed circle of confusion (CoC). The calculator then recommends the larger of the two resulting DOF values, on the rationale that if you specified an acceptable CoC then you must be willing to accept at least that much blur, and if the specified aperture allows a larger step size due to diffraction, then you should use that larger value.

The two calculations end up producing almost the same number when CoC = 0.0011 * effective F-number. Through no coincidence at all, 0.0011 * effective F-number also corresponds to the size of the Airy disk at that aperture. In other words, the wave optics calculation is “just like” running the classic calculation, with a CoC that is automatically matched to the size of the diffraction blur.”

 

Getting to know a 'new' lens

In the last two posts I introduced the Poor Man's Optical Bench (PMOB) tool and showed how you can estimate the location of the on-axis entrance pupil of your lens using a cheap laser leveller.

Knowing: the position of the entrance pupil, but as previously mentioned, assuming it is at a single on axis location; the minimum focus distance and the focus distance of interest, both from the sensor plane; the pupil and optical magnifications; and the aperture number at infinity; allows you then to create your own 'thick lens spec sheet' at a given focus.

In this post, I'll illustrate how to do this at infinity focus, using my 645 Mamiya-Sekor 35mm C N lens. I will also show how to 'calibrate' your lens depth of field scale.

From the lens manufacturer we know the minimum focus distance (MFD) is quoted as 450mm (on this occasion I used this, rather than measure this myself). We also know the infinity focal length is 35mm. Finally, we known the flange distance of the 645 Mamiya system is 63.3mm.

From taking a couple of snaps on a light box, and aligning the images in Photoshop, we can estimate the pupil magnification at infinity as 2.1:

The ‘entrance pupil’ location is found using the laser leveller technique, giving an estimate of 35mm from the lens rear flange surface. Which tells us the location of the entrance pupil, relative to the sensor, is at 35 + 63.3 = 98.3mm:

In the above Photoshop composite, ie I don’t have two laser levellers, we see the two laser lines clearly locating the entrance pupil, relative to the lens rear flange surface.

Having got all the input data, we then open up the Poor Man's Optical Bench (see link RHS) and input all the information:

In the screen grab above we see all the input data and that focus is at 'infinity', ie greater than 10 hyperfocal distances, ie magnification is 0. The other magnification, 0.104. is an estimate at the MFD, but assuming the focal length remains fixed. Once you adjust focus to, say, the MFD, you will need to tweak the focal length, after remeasuring the entrance pupil location and pupil magnification, and getting the optical magnification at that focus, eg as quoted by the manufacturer, ie 0.11 in this case, or measured by yourself.

We also see an estimate of the hiatus (44.9mm), and the hyperfocal distance from the sensor, here based on a circle of confusion of 20 microns.

Finally, we also see a dotted line showing where the flange distance sits relative to the sensor.

For the pano photographer, the above gives us the location of the no parallax point of the lens, ie the entrance pupil.

The next thing we can do is calibrate the depth of field scale.

The 645 Mamiya-Sekor 35mm, being a prime manual lens, has an unambiguous depth of field scale, unlike a zoom lens, but, of course, we don't know what CoC the manufacturer used.

Using the PMOB we can get an estimate by simply counting the number of DoF rotations to go from infinity, ie focused at the hyperfocal at a given aperture, say f/16, to, say, the MFD. This can be accomplished by putting some masking tape on the lens and marking the DoF rotations needed to get from the hyperfocal to the MFD.

Using the f/16 marks on the DoF scale, I estimated the number of lens rotations to get from the hyperfocal to the MFD at about 3.1:

Having set focus in the PMOB to the MFD, we first need to repeat the process of locating the entrance pupil with the laser leveller and measure the pupii magnification, and optical magnification if you wish or take the manufacturer’s value, and enter these values into the PMOB. Once entered, we need to adjust the focal length in the PMOB until the magnification matches the manufacturers 0.11, or your measured magnification. 

Which means, after adjusting the CoC slider in the PMOB, to match the number of brackets to about 3.1, tells me the manufacturer used a CoC of around 48 microns when laying out the scale, which compares well with taking a full frame CoC value of 30 microns and factoring it by the 645 crop of 0.62.

Knowing the DoF scale CoC, it is a simple matter to dial in any hyperfocal infinity blur you wish, or any overlap blur when focus bracketing. For instance, if you wanted to use a CoC of 24 microns, instead of 48, with an aperture set to f/16, you would use the f/8 DoF scale.

Finally, knowing the position of the flange and the overall length of the lens, we can overlay a pretty picture of the lens, say in Photoshop, to enhance the look of our 'lens data sheet':

So, there you have it, using the PMOB and a laser leveller, you can characterise any lens at a specified focus, eg infinity or at maximum magnification.

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