Saturday, September 9, 2023

Latest XPan Emulation Experiment

In this short post I'll show how I've adapted my IR converted Canon M10, with its 4.29 micron pixel pitch, using a 35mm Mamiya 645 lens, coupled to a 645-EF adapter, coupled to an EOS EF to M RhinoCam Vertex Rotating Stitching Adapter.

At 35mm, a suitable rotation is 30 degrees. 

After taking 12 images, four for the Vertex, at three angular offsets, I end up with a near perfect XPan 617 image after Lightroom stitching, using the cylindrical projection.

The resultant, B&W processed, image is 18468 x 6518, ie an emulated digital XPan ’negative’ of 79mm x 28mm. That is slightly bigger than the XPan ;-)

The screen grab looks like this:

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

Thursday, September 7, 2023

Do we still need to exposure bracket?

Today's post processing engines and tools have incredible capability. In addition, using Lightroom as a hub, it's relatively easy to pop in and out of various software packages.

This software capability got me thinking: namely, whereas in the past I would exposure bracket a high DR scene, today an ETTR capture is likely to cover all my needs - at least for digital showing.

As an example, here is a handheld test image, of a high DR scene, taken with my EOS M3. Shot with UniWB, hence the green cast, at 11mm, with my trusty 11-22mm lens, at f/5.6, ISO 100 and 1/100s.

The Lightroom histogram of the RAW capture  looked like this:

As we can see, I ETTRed for the highlights.

My usual, CHDK based, in field workflow when handholding is to also take a +4Ev (insurance) ISO shot, via one of my Lua scripts - just in case I need some help in the deep shadows:

I then used a linear profile, together with a Lightroom preset I've developed, on both ISO images.

After a bit of tweaking and using some third-pary apps, eg Radiant Photo, I ended up with this, made from the ISO 100 capture, that is I didn’t need to cash in my ISO insurance:

The bottom line being, I've convinced myself that for handheld captures, at least for digital showing, I don't need to bracket beyond one additional +4Ev (insurance) ISO capture.

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

Friday, September 1, 2023

Digitally emulating a 30mm Hasselblad XPan

I met up with a good photography friend this last week and was suitably envious when he brought out his 'new' XPan (Mk1) system, in near mint condition, that he had just  purchased with a full set of lenses (this picture is not of his kit).

As I can't justify the cost, some 6-8,000 pounds, purchasing such a camera system, and don't shoot film; I thought I would see how I could digitally emulate his XPan, fitted with the widest XPan lens, a 30mm.

As it would be near impossible to fully emulate the XPan, I decided to focus on two attributes:

  • Getting close to the image size of 65mm x 24mm
  • Getting close to the Angular Field of View at infinity, which is around 94 degrees, horizontally, using a 30mm XPan lens

As I also wanted to create something different, I decided to use the EOS M mount as my digital back, as I have full spectrum, visible and IR M mount cameras: several Ms, an M10 and an M100. All my M mount cameras are converted by Alan Burch.

My starting point is an EOS EF to M RhinoCam Vertex Rotating Stitching Adapter, which allows me to create a 7780 pixel square, stitched, 'quad'. Note the adapter is not electronic.

To provide me the greatest flexibility in focal length optimisation, I decided to use my EOS 24-105mm, F/4L, locked by using the lens twist technique, to the required aperture. In the test I decided to use f/8, which on my IR converted M100, was a little too stopped down, ie diffraction.

Mounting the above on an available nodal rail, a pano, clickable, rotating base, and an Acratech reversed ballhead for levelling, resulted in the following set up.

The position of the infinity, no-parallax, entrance pupil at 30mm, in blue below, was estimated from the PhotonToPhotos optical hub.

Using a field/angle of view calculator from scantips gave me a hint that I should rotate the 30mm lens twice by 30 degrees, which gave me sufficient overlap of the quads, and got me close, but wider, to the XPan 30mm FoV of 94 degrees. That is, ignoring pupil magnification, an infinity AFoV in degrees of around 2*30 + (360/pi)ATAN(quad-sensor-width/(2*focal-length))

After stitching the 12 images, of three quads, in Lightroom, I was then able to extract/crop out a 617 image with about the right field of view of a 30mm XPan.

The proof of principle (IR) test capture, with my converted M100, was, as usual, in my garden. In this test I should have spent more time refining hyperfocal based, infinity focus, but as I was only establishing the workflow, that wasn’t too important.

One of the uncorrected IR quads (7820 pixels square from four rotations of the adapter, that is simulating about a 29mm square sensor) looked like this:

After stitching in Lightroom, using one of my IR profiles, carrying out some toning and a hue-based 'channel swap' etc, the resultant 617 image, 15708 x 5544 pixels in size, looked like this:

If we assume the Canon M100 pixel pitch is 3.7 microns, the resulting 'XPan emulated digital image' represents a sensor some 58 x 20 mm in size, a little bit short of the XPan, but still pretty impressive.

Obviously the above is not really a digital equivalent of an XPan. The need to stitch 12 images is the real problem, but, IMHO, it's not a bad emulation.

Bottom line: if you don't have 6-8 thousand pounds burning a hole in your pockets, with a few pieces of cheap equipment you can get close to digitally emulating a 30mm focal length XPan, using a cheap Canon EOS M mount camera.

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

Sunday, August 27, 2023

Happy 10th Anniversary to Magic Lantern Dual-ISO

Although I don't have my Canon 5D3 anymore, having converted to an R, I still have lots of 'old' 5D3 captures.

Since A1ex at Magic Lantern introduced Dual-ISO ten years ago, the basic idea hasn't changed. That is, ML samples half of the sensor at ISO 100 and the other half at, say, ISO 1600. If you mix these two, with the Dual-ISO processing App, you can get almost the entire dynamic range the sensor is capable of (around 14 stops).

Of course what has changed in those 10 years are all the other post processing tools.

As a Lightroom and Photoshop user my 2023 post processing workflow goes like this:

  • Process the captured Dual-ISO, from within LR, with the ML Dual-ISO Converter, thus creating a base DNG RAW
  • Apply a linear profile to this DNG, ie to take back control from Adobe ;-)
  • Using the LR masking feature, and curves, carry out base processing on the DNG, ie so far I haven't touched a LR slider
  • From here go whatever way you wish, ie finish things off in Lightroom, pop in and out of Photoshop, use other apps from within LR, eg Radiant Photo, Luminar Neo, etc

So what does the above achieve?

Well here is a screen grab of what the RAW looks like in Lightroom:

The image, captured in Iceland in Feburary 2017, was shot on my 5D3 at a base ISO of 100, at f/13, with a shutter of 0.8s. Plus it was ETTRed using ML.

The Lightroom histogram of the base image looks like this:

After using the above workflow, the image, although not an award winning one, looked like this:

Finally, another example from Iceland, including dust spots ;-)


So Happy Birthday Dual-ISO and thank you A1ex: wherever you are.

Saturday, August 19, 2023

Medium Format Panoramas with the EOS R

In previous posts I've covered how I use sensor bracketing to create larger formats than the native sensor size, eg: here and here, and in many other posts.

One of the advantages of using mirrorless cameras is the wide availability of adapters, that allow you to adapt lenses with a larger image circle, for example, in my case:

  • EOS M camera to EOS lenses
  • EOS R camera to Mamiya 645 lenses

In this post I'll discuss my latest experiment in getting close to a digital 617 film camera, for example the FujiFilm G617, some 60x170 mm.

My starting point is a RhinoCam Vertex Rotating Stitching Adapter from Fotodiox, which connects my EOS R to one of my Mamiya 645 lenses.

Using this set up I'm able to create 1x1 645 images some 8896 x 8866 in size, from four brackets, ie a 1x1 quad.

To emulate the FujiFilm G617 I additionally need to carry out a pano rotation. To ensure sufficient overlap at 45mm, and to exploit a clickable pano rotator I already have, I selected 45 degree of rotation between each 1x1 quad captures, ie 3 clicks of 15 degrees.

To illustrate how all this turns out I took a test image in my garden, albeit on a windy day :-(, using my EOS R and a Mamiya 645 45mm lens.

For reference the 1x1 645 quad looks like this (note I didn't get the ETTR exposure right in this test):

The above quad is 8896 x 8866 in size and, of course, shot through a MF lens.

Repeating the above twice more, every 45 degrees, ie obtaining three quads worth of images, 12 full frame brackets, results in the following Lightroom pano merge (in this case I used spherical projection):

The above image is 22923 x 8963 in size: some 205 MP image. As I said above, I didn't attempt to nail the exposure, so the sky is blown out, as I was just testing my workflow.

After some post procesing the image looks like this:

A digital 185 MP, 617 image, 22922 x 8090 in size, taken with a Mamiya 645, 45mm lens with an EOS R 'adapted digital back'.

All good fun stuff.

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

Saturday, May 13, 2023

QDFS Field Testing

In this short post I'll discuss the latest tweaks I've made to my Canon M3 Quasi Depth of Field Script (QDFS) and show a few snaps from a recent field trip to the National Trust's Stourhead property.

When it first opened in the 1740s, the garden at Stourhead was described as 'a living work of art'. Its designer, Henry Hoare II – or 'Henry the Magnificent' – was one of a small group of 'gentleman gardeners' who used their large estates to create a personal landscape. Henry was inspired by his travels around Europe and, while Stourhead's garden has developed over the centuries, those original inspirations can still be seen today.

All the images captured at Stourhead were taken hand held with the help of the QDF Script, ie optimising focus and exposure bracketing.

The latest version of the script, downloadable from the right, now includes a wind bracketing option, which gives you your base bracket and an additional bracket at the same exposure, but at a higher ISO, and thus at a faster shutter speed. This use case covers wide angle capture, where the forground objects may be more visibly impacted by wind than the background. Typically you would use 3-4 Ev as the wind bracketing offset.

 I've also changed the UI and its functionality a little, as shown below:

The UP button now toggles between Canon shutter speed and ISO adjustment modes.With the DOWN button toggling the console on and off, with the console's position set in the script's menu.

Finally, the script now checks to see if the camera is in manual focus mode, and, if not, sets it to MF. It also checks and ensures the wheel is always set to shutter speed adjustment, irrespective of the camera being in ISO or Tv adjustment mode at start up. Noting, of course, you can switch between Tv and ISO adjustment modes with the UP button.

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

Sunday, April 30, 2023

QDFS: A few handheld enhancements

In this post I'll discuss the latest version of my Canon M3 Quasi Depth of Field Script. 

In addition to some UI changes, eg focus distance is now stated in cm, I've added some bracketing enhancements. The latest version may be downloaded from the link on the right.

The new menu options look like this:

#coc = 15 "CoC (um)" [5 30]
#brak = 0 "X bracket mode?" {ISO Tv HandH Auto->H}
#b_val = 0 "X Bracketing Value" {Canon 1Ev 2Ev 3Ev 4Ev 5Ev}
#sleep_time = 0 "Delay (s)" [0 10]
#dis = 1 "Display" {#Bracks Focus}
#lensmag = 0 "Get Mag" {Off On Dynamic}
#reg = 1 "H/x Reg Dis" [1 3]
#offset = 1 "Console offset" [1 12]
#title = 1 "Title Line" {Off Full Exit}
#ettr_zero = 3 "ETTR zero count" [0 20]
#hhmin = 30 "HH Min Tv (1/x s)" [10 100]

Here we see the two new exposure bracketing options. One for when hand holding (HandH) and one for auto bracketing (handholding or not), from an exposure set for the shadows, with the script auto bracketing until the ETTR exposure is reached. The bracketing steps may be set at 1, 2, 3, 4 or 5 Ev (b_val).

The ETTR 'zero' count may be set from 0 to 20, ie how many counts are allowed in the top 1/10 Ev of the histogram. In addition, when using the HandH option, you can set the slowest acceptable handheld shutter value, with the script adjusting if the 1/focal_length criteron is not met.

The handheld (HandH) option, which works well in high dynamic range environments like churches, is best used in the following way:

  • Set the Ev value to 4 or 5 Ev
  • Set the ISO to 100 (note you can use a higher ISO if necessary)
  • Set focus
  • Use the script (RIGHT button) to set an ETTR exposure. The script will check it meets the handheld criterion
  • Trigger the bracket set and the script will take the following three brackets
    • Image 1 at the ETTR ISO 100 setting
    • Image 2 at the handheld shutter value at ISO 100
    • Image 3 at the handheld shutter value and at an ISO of the set Ev value, eg 4Ev = 1600

The Auto->H (where H = hightlights) can also be used for handheld bracketing, ie where shadow noise is likely to be an issue in a single image capture. Of course, the Auto->H option can be used to take non-handheld bracket sets as well, ie at any ISO.

  • Set the Ev value between brackets, eg 2Ev
  • Set focus
  • Set the shutter to the handheld value for the focal length you are using, eg on a WA lens 1/30s, or slower if you haven't been drinking a lot of coffee
  • Adjust the ISO, up to, say, 3200, until the histogram (Canon or CHDK) indicates a suitable ETTL state. Adjust aperture and refocus as required
  • Trigger the bracket set and the script will take the following brackets
    • Image 1 at the manually set ETTL and ISO setting
    • Image 2 to n, at the ISO setting and by adjusting the Tv value until the ETTR condition is met

As an example of using the auto option, here is a handheld test image I just took from inside my dark garage, looking out. The focal length was 11mm and the base shutter was set to 1/30s. The ISO was set to 3200.

The script then took the following additional ISO 3200 images until the ETTR criterion was met: 1/125s and 1/500s.

The resultant test image, after processing with PureRaw 2 and Lightroom, looks like this:

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