Tuesday, October 19, 2021

M3 LBS minor update

In the last post I introduced the LE/NR and Super-Resolution features in the M3 Landscape Bracketing Script. As a result of some testing, I've refined/simplified the UI.

The top half of the menu now looks like this:

Here we see that a Super Resolution bracket set has been requested under the Focus Bracket? menu item. The number of super-res images to be taken is now defined via the negative ND feature. A -3 value, as above, takes the script to take 8 images. A -5 value would result in 32 images.

There are now two focus move options that attempt to introduce image to image pixel dither. In the above Off is shown, meaning that no focus dithering will be attempted, ie the super-res bracket set 'just' captures the required number of images for either LE or NR post processing.

The two differ schemes are -+ or ++.

In the above we see that the -+ scheme has been selected, which will adjust focus either side of the point of focus, ie half and half. Each time adjusting focus towards infinity, having first re-positioned away from infinity. 

In the ++ scheme, shown below, focus differing is attempted from the point of focus, towards infinity. As stated in the last post, pixel dithering via refocusing is not a guaranteed approach, however, if the angle of view doesn't change, at  least you will have a LE/NR bracket set.

As a reminder, the UI looks like this, ie giving you constant focus feedback until you run a focus bracket set:

In the above we see that the console option is switched on, thus giving feedback from the script. This option can be disabled if required.

In this above, the top bar shows:

  • We are focused at 259cm from the sensor
  • That 2 focus brackets are required to get to the hyperfocal
  • That we are at 13mm focal length
  • That the shutter is set to 1.3s
  • That the near Depth of field is at 130cm
  • That the defocus infinity blur is at 16micons, in other words we are focused just short of the hyperfocal, which is based on a 15um overlap setting, as shown above in the menu
To capture the super-res bracket set, all we need to do is to push the the M-Fn button, which acts as the script's auxiliary shutter button. In this case, because we are not requesting a focus bracket set, the script will keep running, ie you can repeat the super-res bracketing as many times as you wish, adjusting focus and exposure in between captures.

As implied above, the noise reducation or long exposure bracket set operates in a similar way to that of the super-res one: but in the LE/NR case focus is not changed at the LE/NR bracket set is captured at the 'infinity' focus position, as is the sky bracket, ie after focus bracketing. 

Friday, October 15, 2021

M3 Landscape Bracketing Script: Now with ND and Super-Resolution bracketing

I've discussed multi image bracketing for ND and Super-Resolution in previous posts: that is taking a bracket set of images for post processing to simulate a long exposure or provide the data to create an up-scaled and/or noise reduced image.

The idea is simple. For LEs just divide the required time by the shutter speed and take this many images for 'averaging' in post, eg to simulate movement in water. This feature works well when you either don't have an ND filter with you, or you don't have a stronger enough one.

For Super-Resolution processing the procedure is similar, but we need to introduce small amounts of sensor movement between images. That is take at least 4 images, or as many as you wish, that are up-scaled and statistically averaged in post. This technique is best applied to images with little/no movement. The Super-Resolution bracketing exploits the focus breathing that occurs when changing focus, ie to simulate pixel shifting at the sensor. But note, this effect may not manifest itself on every lens or at every focus position or focal length, as it is dependent on the lens exhibiting lens breathing, ie a change in the angle of view, in the area of focus. However, even with no movement, you will still have a noise reduction bracket set.

I'm pleased to announce that I've incorporated both bracketing schemes into my M3 Landscape Bracketing Script: which can be downloaded from the right as usual. The top part of the menu now looks like this:

@subtitle Bracketing Options
#mode = 0 "Focus bracket?" {Off X2INF Min2INF Manual Min2X SupRes}
#bracket = 0 "Exposure bracket?" {Off 1(4Ev) 1(3Ev) 1(2Ev) 2(2Ev) 3(2Ev) ISO Auto Wind3Ev Wind4Ev}
#sky = 0 "Sky Bracket?" {Off 2Ev 3Ev 4Ev 5Ev 6Ev ETTR}
#ndf = 0 "ND?" [-5 30]

@subtitle Bracketing Settings
#infinity = 3 "Infinity Focus (xH)" [2 4]
#overlap = 15 "Overlap (um)" [5 30]
#hilit = 5 "% Histo HiLit" [1 30]
#start = 1 "Histo Upper Quartiles" [1 4]
#pmag = 1 "Assumed Pupil Mag" [1 6]
#isoval = 0 "ISO Bracketing Value" {400 800 1600 3200}
#supres = 4 "# SupRes shots?" [4 16]

To use the ND/LE feature, simply set ND to a non-zero number. If the number is negative the bracket set will simulate that ND value, eg -2 will take 4 images for processing a simulated 2 stop ND filter; whereas -5 will take 32 images to simulate a 5 stop filter.

Note that the negative mode can also be used to create a noise reduction bracket subset. That is a value of -4 will create 16 images, for a NR of 4 after processing in post.

If the ND value is positive, eg 2, this is asking the script to take the required number of images to simulate a 2s exposure. In order to keep the number of images to a minimum, the script first adjusts the aperture to the maximum it can, ie up to f/22 if the base shutter allows. The shutter is then adjusted to ensure the exposure is the same as the base. 

The Super-Resolution technique will only work on a lens whose focus motor can be controlled, eg the EFM lenses. This new feature works best when you set the base focus at the hyperfocal, as the lens moves towards infinity, at the smallest step it can, to simulate sensor pixel shifting.

The number of images is set in the supres menu item, ie between 4 and 16. Also, the super-resolution bracket set can only realised with focus bracketing set to manual. Whereas the ND/LE/NR bracket set will be created as part of a focus bracket capture, eg X2INF.

Both bracket sets are post processed in, say, photoshop, using the following workflows:

  • For LE/ND processing ingest the images into Photoshop and stack into a single image. Align the images then either use the Photoshop Merge script on the right or manually adjust the individual image's opacity, ie halving the opacity each time with the bottom image at 100%. Then flatten the image.
  • For Super-Resolution the process is similar, however,after stacking and before aligning, upscale the image by 200%. After processing you can then export the Super-Resolution image back to Lightroom, or downscale first. See here for more information on the Super-Resolution technique.

You can also use Smart Object statistics, eg median, but this route is slow if you have a large number of objects.

The following is a Super-Resolution test image I just took with my M3 using the 11-22mm M lens at 11mm. The aperture was set to f/8 and the shutter to 1/40s. I requested a 10 image Super-Res bracket set on this occasion, and was lucky that there was nearly no wind to ruin the test.

If you zoom in on the image it is easy to see the lack of noise in the shadows and the general cleanness of the image, noting that no NR was used in post.

With the two new bracketing features, it is easy to create complex bracket sets via one or two button pushes. For example you could set up focus bracketing for a deep focus capture, plus taking an ND/LE bracket set to layer in in post, plus an ETTR sky shot to, once again, layer in in post.

I will discuss post processing in a future post.

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

Monday, September 20, 2021

Landscape Bracketing Script (M3): now with a simulated ND filter option

Just a quick post to say I've brought the M3 version of my CHDK Landscape Bracketing Script, into line with the non-M3 version.

The M3 version, downloaded from the right as usual, now has a menu item called "ND Filter?", with values of 0 to 5.

If 0 is selected then no ND brackets will be taken. If the value of this menu item is between 1 and 5, then a simulated ND bracket set will be taken, as part of the focus and exposure bracket set.

An ND2, will take 2 images that you can post process, whereas an ND5 will take 32 images. Each ND bracket set can be processed in Photoshop, for example, to create a Long Exposure image for blending with the others in the bracket set, eg the focus images and the sky ETTR capture.

The ND images are taken at the foreground exposure value, ie the one used for focus bracketing.

As with the sky exposure bracket, the ND filter bracket set is taken at the infinity focus point that you set, eg three times the hyperfocal, say.

Once captured, the bracket set is easily identifiable in Lightroom, as the script makes use of dark frame bookends at appropriate places, eg:

In the above we see that the entire bracket set has bookends at the start and end of the bracket set, and the ND set is also delineated, eg the 4 images towards the end, in the above example. Also seen are (4) focus brackets, at the start: two before the hyperfocal, one at the hyperfocal and one at, in this case, 3 times the hyperfocal, for a defocus infinity blur of about a third of the overlap CoC, which was set at 15 microns in this test capture.

The script automatically took the focus brackets, as, in this case, I had selected the X2Inf option. Thus all I needed to do was to focus on the foreground point of interest, note the number of focus brackets and accept or adjust the aperture, focus or focal length.

Then, with a single button press, the M3 captured a perfect focus bracket set, plus capturing a simulated ND bracket set for 'statistical processing in Photoshop, and an ETTR sky image at infinity. 

Once the focus and ND bracket sets are pre-processed, these two images can be blended with the sky ETTR image, eg using masks.

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

Wednesday, September 1, 2021

If it's good enough for a Large Format camera; then it's good enough for my Canon M3

Once you get into photography you begin to look at the various categories of equipment. From large format film cameras down to point and shoot digital technology.

From my perspective, with a bias towards the science and technology of photography, I'm always interested to look backwards for 'new' ideas, ie ideas that we can exploit today.

This post is about one of those necessities from the large format, view camera world, that is virtually ignored today. Namely a dark cloth, which is also called a focusing cloth or hood, The dark cloth being a piece of light-proof material that covers your head and the back of the camera. It eliminates stray light to allow for proper viewing of the relatively dim image on the camera ground glass during framing and focusing.

Although today's digital cameras don't require us to inspect focus on a piece of ground glass, we often find ourselves looking at the LCD screen , eg to read camera info, carry out focus peeking or, in my case, drive Magic Lantern or CHDK.

But try and look at a camera's LCD screen in bright sunlight, or if your eyes are 'getting older', as mine are.

I've tried various 'solutions', but I found all of them lacking at some level. Plus things can get complicated if your camera has an articulating screen, rather, say, than the fixed screen on my 5D3.

Also, as a photographer who likes getting low, I envy the cameras of old, where you can look down into the camera:

As my 5D3 has a solution in the form of the Swivi S5 (see below), I decided to 'hack' my M3.

As I didn't wish to buy more 'stuff' I decided to use what I had and not to compromise my base Canon M3 configuration, which looks like this:

That is any solution needed to fit around a cage and a handle, and enhance my low level photography needs, when I have the screen deployed like this:

The base set up ended up looking like this, where I adapted a collapsible Hoodman Loupe, with a diopter adjustment, via a cold shoe mounted, miniture ballhead:

But this base arrangement still suffers from light hitting the screen.

The final configuration benefited from me having a wife who is an expert sewist. She quickly knocked up the following Mark 1 version of my idea, which will likely end up the final version for me. Thank you Jean :-x

Here we see my 'dark cloth' for a DSLR :-)

So far it's a 100% success: allowing me to use the camera in bright sunshine, low on the ground, whilst focus peeking and controlling CHDK scripts.

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

Monday, August 30, 2021

M3 Landscape Bracketing Script: minimum focus to focus position mode

Just a short post to say I've updated my M3 bracketing script to include a new auto focus mode, to cover when you wish to focus bracket from the minimum focus distance of the lens, to a fixed point. For example, when you don't want a sharp image throughout the scene.

To enable the new feature simply select it in the menu. But remember the caveat with this script, it’s not designed for macro focus bracketing at high magnification.

Once selected, to use this new mode simply:

  • Set the lens to the minimum focus and focus the camera on the nearest part of the object of interest, ie by moving the camera - the front of the tea bag in the example below;
  • Then move focus, with the lens, to the far part of the object of interest, ie the top of the tea bag in this example;
  • Then run the script.

To get an estimate of the number of focus brackets, simply take note of the difference between the number of brackets reported at each focus station, ie the minimum and the farthest focus point of interest.

Finally, you can also use sky bracketing with the new Min2X feature.

In this example, shot at F/4 at an 11mm focal length, the script took 6 images, which I processed in Helicon Focus:

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

Addendum to "Continuing insights into Macro Photography: Part 2"

In part 2 I showed how we can work out the 'best' aperture for macro photography based on the following variables:

  • The optical magnification (m)
  • The pupil magnification (p)
  • The acceptable total circle of confusion (c)
  • A factor, k, to account for the post production impact of the diffraction, ie 0 means ignore diffraction, 0.5 assume a 'weakish' impact and 1 assume the 'full' Airy impact.

I also showed how you can find the pupil magnification through the PhotonsToPhotos optical bench hub. Of course if your lens is not in the list of lenses, you will need to measure or guess the pupil magnification yourself.

As many macro photographers will be using a lens set to a specific optical magnification, there is no need to worry knowing the focus distance, as we do in non-macro photography. We thus 'only' need to solve the following to arrive at an estimate of the total depth of field (d) in mm; where m, p, c and k are the four variables that you need to know to match your camera/lens settings and presentation needs:

Note that c in the above is in mm, with the other input terms being dimensionless.

As some will look at the above and be intimidated by the maths, here is a link to a WolframAlpha page (no need to supply any personal details) that allows you to input your m, p, k and c values on the input line at the top of the WolframAlpha screen; with WolframAlpha doing the maths for you to solve for d and, on the way, highlight the optimum aperture (N). Note that you need to select approximate in the Solution box to get a decimal output, also use a small k value to switch off diffraction, say 0.1, else you will get a ‘no solution’ result.

As an example, lets take a Canon 100mm macro lens and use the PhotonsToPhotos Hub to find the pupil magnification at an optical magnification of 1. Note the aperture of F/10 is arbitrary, ie the pupil magnification does not change with aperture:

Here we see that at a magnification of 1, the lens has a pupil magnification of 0.28. Let's assume a circle of confusion of 0.03mm, ie 30 microns, and that we can use our software tools to recover some of the diffraction softening, thus we will use a 'weak diffraction model' and a k value of 0.5.

Plugging the above into the WolframAlpha link gives the following:

Here we see that, if shooting with the Canon 100mm macro at unity magnification, we will maximise the diffraction aware depth of field by shooting at F/6.5, which will result in a total depth of field of about 1.3mm, ie about 0.65mm either side of the plane of focus.

The above is all useful information if we are focus stacking with a rail (more on this in a future post). 

If handholding, single shooting or attempting to focus bracket by moving the camera's position relative to the subject, this depth of field is very challenging, unless you are Thomas Shahan, say :-)

However, we have a few things that can help those of us that need it. 

First, modern sensors tend to have a good resolution, thus, although a magnification of 1 is great, we could get away with a magnification of, say, 0.5, ie about half the linear resolution on the object, relative to unity magnification.

Second, we have software that purports to 'recover' the image quality by 'AI algorithms', for example the new Adobe Enhance feature.

Based on this, let's now look at backing the optical magnification off to, say, 0.5; which results in the following lens characteristics:

Here we see that the pupil magnification has now changed to 0.58, resulting in the following DoF estimate:

That is our diffraction aware depth of field is now estimated to be about 5.3mm, shooting at F/16. Although the object will take up about a quarter of the sensor area of the previous set up, with a modern sensor this should be OK: as long as we are not seeking to create too large a print and the exposure is still ok. 

I hope this addendum has helped some, and, as usual, I welcome any feedback on this post or any of my posts.


Sunday, August 29, 2021

Continuing insights into Macro Photography: Part 3

In the last couple of posts I've addressed some of the theory behind macro photography; in particular the depth of field and impact of diffraction when undertaking macro photography. 

We have seen that, although we can ignore lens asymmetry, pupil magnification, for non-macro photography, we can't when shooting at magnifications greater than, say, 0.5.

We therefore know that with depths of field measured in a couple millimeters, at best, and likely sub millimeters, attempting to handhold during macro photography is a skill that needs to be practiced. 

So far it is a skill I have yet to perfect. For example, I went out yesterday with my Canon 100mm macro, attached to my 5D3, and tried to grab a few handheld shots. 

I had previously tried without a flash, but on this occasion I used a flash with a diffuser, to soften the light and reduce harsh shadows.

From these early experiments, flash and a diffuser is clearly the way to go.

Although I will carry on trying to perfect my handheld skills, my instinct is to move on to the next macro technique that should give better results than handholding: namely focus stacking.

So, to bring this post to an end, I'll simply post a few images from yesterday's shoot.

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