Friday, December 29, 2017

You don’t need Photoshop

Although many/most who use Lightroom also these days have Photoshop, some just don’t like the ‘heavy lifting’ required for the round trip to Photoshop, or even the ‘pain and grief’ of learning PS. This post is for those that prefer a LR-based post processing workflow.

The starting image is this capture of a church near us. It was taken with an Irix 11mm Blackstone lens; it is a single ETTRed image with a base exposure at ISO 100, and F/11, of 1/8s.

The first step is to carry out any lens correction and, unless you wish to manually tweak, select the ‘best’ white balance setting for your vision, eg Daylight in this case. Typically I would then bring my highlights to 0 and my shadows to 100 (and back off both as required) and then adjust the exposure, -1.3Ev in this case, to arrive at a basic post processed image:

Having got my basic exposure 'ok', I typically next attack composition as this will have an impact on the rest of my post processing. In this case, I wanted to correct the 11mm, hyper wide angle effect, and bring the near field cross into better alignment with the church. The best tool to do this is the guided transform in LR. Simply place you four guidelines to achieve the effect you are after. Here is a screen capture showing the process:

The final phase is to crop the image to your liking, clean up any extraneous ‘stuff’ using the LR spot removal brush, and ‘relight’ the image, ie adjust exposure globally and locally, to your choice using the radial and graduated local filters. Apply a final sharpening and carry out any other global adjustments, eg relook at WB, to arrive at this final image.

I hope this short post has helped those that are still trying to get their head around post processing. Once you have a workflow sorted out and understand a few tools, Lightroom is a very powerful post processing environment: that is until you wish to use luminosity masks etc and undertake radical surgery on your image; but that’s another story for another time ;-)

Wednesday, December 27, 2017

Understanding the Irix 11mm Depth of Field

Let me say up front, the Irix 11mm is a very impressive lens. It has very low distortion and has an incredible field of view. The lens is a manual one, although aperture is fully electronically controlled.

Being a (hyper) wide-angle lens, the depth of field is huge, but, at first, some may be confused by the depth of field scale, especially if they are used to using ‘standard’ depth of field tables, without thinking about what they mean.

Readers of my posts know that the ‘standard’ DoF tables, that you typically see online, assume a Circle of Confusion criterion, used when calculating the defocus, of around 30 microns on a 35mm, ie adjusted down by the crop for smaller format cameras. Many tables also ignore diffraction. Such tables are not that useful if you use them to ‘just’ set the hyperfocal focus, as you will not achieve high quality focus in the far field (read some of my previous posts on infinity blurs).

There are some great DoF apps out there, which I have previously spoken about, eg TrueDoF-Pro; and, of course, for Canon users, the ultimate DoF app is my (in-camera) Focus Bar script. As the Irix doesn’t communicate focus distance, the FB script is useless.

However, other than my Focus Bar, the apps don’t tell you much about the infinity blur, ie as you focus past the hyperfocal point.

However, the Irix has a killer feature, that is usually missing on modern AF lenses: a usable Depth of Field scale, which can be utilized to:

  • understand the depth of field at a given focus point
  • set the hyperfocus distance
  • carry out focus stacking

However, to use the DoF scale, it is critical to understanding how the Irix designers laid out the scale. For example, if we ignore diffraction and ‘just’ use the defocus blur to calculate the hyperfocal distance at 11m and F/16, using a CoC (blur) of, say, 30 microns, we will get a hyperfocal distance of about 0.26m.

However, if we set the Irix infinity mark to the F/16 point we get a hyperfocal distance between 0.7 and 1m. Clearly the Irix designers didn’t use a ‘normal’ CoC of 30micron,  ignoring diffraction. Thank goodness!

It is easy to estimate that, at the infinity end, the Irix DoF scale appears to be based on a defocus blur (nee defocus CoC) of around 9 microns. This is very exacting and if used will result in high quality focus results.

We also know that defocus blurs less than two sensor pixels represent a sensible lower limit when we are using infinity-biased focusing, ie focusing beyond the hyperfocal, but short of the (optical) infinity.

On my Canon 5D3, this limit is 2x6.3 microns, say 13 microns. The Irix is thus well placed to deal with cameras with high density pixels. For example the 5DS has a pixel pitch of 4.14 micron, ie a sensor line-pair limit of just under 9 microns.

At distances shorter than the hyperfocal, the Irix DoF scale appears to make use of a defocus blur of less than 9 microns, ie according to focus position and aperture, anything from 6-9 microns.

So what does this all mean. Basically, using the Irix DoF scale means you will get high quality focus: all assuming the scale is distance calibrated. I did a quick and dirty test, by focusing on an object at 1m and 0.4m away and both seem to indicate the Irix focus scale was spot on, ie I don’t need to recalibrate my lens yet :-)

Summing this up, and based on one day’s worth of experiments, I would say an optimum workflow, at least to get you going in the right direction, would be to set the Irix 11mm to F/8 or F/11, ie keep away for the high diffraction F/16, and use the DoF scale to either set the hyperfocal or carry out a focus stack.

Here is an image to illustrate the hyperfocal setting at F/11, ie suggesting a defocus CoC of around 8 (sic) microns at F/11:

As for landscape focus stacking, it's simple. Take this F/11 example workflow:

  • set the Irix to infinity, using the Irix’s click indication, to take your first shot with an infinity blur of zero, and note the near depth of field is indicated at about third between the 1 and 2m marks
  • refocus the lens so the previous near depth of field is now aligned with the F/11 far depth of field lens mark and take a shot. Note the new near depth of field is about 0.5m
  • refocus the lens so the 0.5m is aligned with the far DoF F/11 mark, which indicates a new near depth of field of about 0.35m, and take your second shot

Use your focus stacking software to blend the three images to achieve an incredible, high quality, focused image from about 0.35m to infinity.

As I explore the Irix 11mm I’ll be writing more posts, but at this stage I’ll simply say, the lens looks like it is going to be a key part of my camera bag. For instance, this test image was taken when I was out doing errands. I hope you agree it shows off the Irix as an unusual lens.

Tuesday, December 26, 2017

Irix 11mm Blackstone

Merry Christmas to you all and I hope you got a few Christmas goodies, like I did :-)

My star present was an Irix 11mm Blackstone lens. 

The Irix 11mm is a manual focus lens, that doesn't report distance to my Canon cameras, hence my Focus Bar script wont work. But, as we will see that is irrelevant with this lens.

Unlike many/most modern AF lenses, the Irix lenses (they do a 15mm prime as well) come with a hyperfocal scale. The lens can also be infinity calibrated, if needed. The (Swiss) manufacturers have decided to use a very high quality circle of confusion to create the focus scale. I estimate a CoC of some 9 microns.

The 11mm is an F/4 lens and the focus ring has two really nice features. A 'click' at infinity and an ability to lock the focus. The barrel distortion is low at just over 3% and the diagonal angle of view is a very meaty 126 degrees.

Although my Focus Bar script doesn't work with this lens, the depth of field scale gives you a simple way to achieve your hyperfocal distance, infinity distance and do focus stacking. For example, here is a four image focus stack, taken from a Magic Lantern ETTR exposure and a 100/800 Dual ISO.


The closest object was less than a foot away.

I  hope to be taking the 11mm Irix out into the field over the coming months and will report my findings in future posts.

Wednesday, December 20, 2017

The User Experience

I'm writing this short post in the spirit of passing on my humble learning, in order to help others trying to script in Magic Lantern's Lua.

Basically, scripting is all well and good,  ie getting the syntax and 'equations' right; however, a good script can be let down by a poor/weak User Interface (UI): which I think covers: usability and user experience.

Having now reached the 'script and maths' is right stage, I realized my two main scripts (The Focus Bar and The Toggler on the right) were letting themselves down with respect to their UI.

Of course I can only talk about this through my (old) eyes and how my brain works, but I was clear to me (pun intended) that the UI needed attention. For example, font size and font colours (foreground and background), plus message positioning.

I've therefore attempted to get a 'better' user experience and welcome any feedback on what I've tried to do.

Saturday, December 16, 2017

“There are two kinds of people in the world, those who believe thereare two kinds of people in the world and those who don’t.”

Ok it’s an old joke but it does sum up those that read my blog, eg those that use my Focus Bar and those that don’t ;-)

But it also is a serious observation on how we think/work differently to each other. For example, some like thinking/learning through images, others through text.

So the latest version of FB (downloadable on the right) adds some additional information to help you decide when to stop focusing as you approach ‘infinity’, irrespective of what type of person you are. 

It provides infinity focus info in two ways. You still see the infinity (vertical and visual) focus breakdown, but now you also, when in ‘full info mode’, get numerical feedback via the ‘Focus Quality Factor’, in addition to the near depths of field data.

The FQF is simply the % increase of the defocus (sic) infinity blur relative the hyperfocal defocus blur (an FQF of 100%), which, as we know, is the minimum acceptable (diffraction corrected) blur that we set in the ML menu as the CoC; as focusing beyond the hyperfocal means that infinity blur gets less and, of course, becomes zero when we focus at infinity.

But we also know that we can not resolve line-pairs less than two sensor pixels. Thus the Focus Bar uses the 2xsensor limit blur to define the maximum focus quality.

These next two screen shots show the FQF in action:

As we can see in the top screen capture, we are focused at 1.27m and the infinity focus breakdown is shown on the right, ie the white total CoC criterion, as set in ML, the blue total blur at infinity, the yellow shows the diffraction component and the green bar shows the defocus component. 

Because we have the Full info selected in the FB menu, we also see the textual (data) on the left, ie the near DoF based on the CoC criterion is 55cm, the near DoF based on the infinity defocus blur is 64cm and that based on twice the infinity defocus blur is 43cm. We now also see the FQF, which is 137%, relative to the hyperfocal point.

The second screen capture shows that we have refocused towards infinity and are now focused at 1.94m. The visual feedback on the right tells us that we are focusing beyond the sensor limit, as the green bar has turned red, ie we shouldn't focus towards infinity anymore and could afford to back off. The focus bar has also turned cyan over the entire DoF, meaning that, once again, we are less than the sensor limit.

We also see, on the left, that the FQF has maxed out and is telling us that at the camera settings we currently have, we can't get a (defocus) FQF greater than 170%.

In the end it is all down to you to decide what information works best for you, however, there is no doubt about it, the Focus Bar provides the best info available, in any camera!