Wednesday, April 14, 2021

M3 Bracketing: Now with manual focus bracketing

Those that have been following my Magic Lantern DOFIS developments will know that I introduced a so-called 'traffic light' feature into ML DOFIS, that tells you the depth of field (DoF) state of your current focus, relative to the last image captured. 

I'm pleased to say that this manual focus bracketing aid is now available in M3 Bracketing.

The feature is enabled via the menu:

In the above screen grab we see the new traffic light feature is switched to be on: it is either On or Off.

The background behind the M3 Bracketing implementation is as follows:

In the above we see the near and far DoFs of the last captured image. Until you take an image, when M3 Bracketing is running outside of ALT mode, you will not see any traffic light feedback.

In the second bar down we see the current focus being at the same position as the last captured image. In this case we see both the left and the right hand traffic lights are YELLOW. You can therefore return to the exact focus position as the last captured image by just refocusing until you see two YELLOW traffic lights.

In the third bar down, we see we have focused towards the macro end, thus the current near DoF is less than the captured image's DoF cover, but the current far DoF has a positive overlap with the captured image's DoF. In this case we therefore see a RED and GREEN set of traffic lights.

The fourth bar shows the situation where there is a near and far focus gap between the last captured image and the current point of focus. So we see a RED/RED display.

The fifth and sixth bars show what focusing towards infinity looks like.

Thus, all we need to do is take an image and then refocus in any direction, until M3 Bracketing info bar tells us when to stop to take a, perfect, focus bracket. That is, refocus until both go RED and then back off your focus until you see GREEN in one of the traffic light.

To illustrate how things look in the camera, the following screen grabs are illustrative. Note I have my style set to B&W in camera, to help me ‘see’ my composition clearer, rather than get diverted by colours in the scene,

In the above we see M3 Bracketing running in ALT mode. In this mode 'all' we can do is refocus and initiate auto focus (and exposure) bracketing, from near to infinity.

To use the new traffic light feature for manual focus bracketing, you first need to press the ALT button, to exit ALT mode. The script will continue working, although you are now outside of ALT mode. The screen will look something like this:

Here we see the M3 Bracketing info bar is still providing all the information, but now, as we are out of ALT mode, we can take images.

In the above I focused to an infinity blur of 10 microns, ie at about twice the hyperfocal: in this test the overlap CoC was put at 20 microns. We see I was using an 11mm focal length and we was focused at 154cm from the sensor, giving a near DoF of 554cm. 

Remember that M3 Bracketing uses a thick lens model and includes pupil magnification. It thus is about the best you can do, albeit we are still dependent on Canon giving us the 'correct' focus distance.

So let's take a picture:

In the above screen grab we see that none the info bar has changed, as I haven't yet refocused. But we now see the two YELLOW traffic lights, confirming I was indeed at the same point of focus as the last captured image.

As I’m at infinity, with a 10 micron blur, I needed to focus bracket towards the macro end, ie away from infinity, all the time recovering more near depth of field.

As I refocus, away from the position of the last captured image, we see the left hand traffic light immediately go red, but the right hand traffic light stays GREEN; telling us we have a positive focus overlap. All I needed to do was keep refocusing until I reached a point where I saw two RED traffic lights, telling me I now had a focus gap:

At this point, I could accept the focus, as it's only just gone RED, or refocus until I saw a GREEN traffic light on the right. If you set the overlap blur to slightly lower than your overlap requirement, you should be able to take an image as it just goes RED, ie not bothering to refocus to GREEN. Your choice.

The latest version of M3 Bracketing may be downloaded from the right. In this release I've also tried to address a few of the CHDK vs Canon UI issues. For example, when manually focus bracketing, outside of ALT mode, the info bar will disappear after an image capture. You can force the bar to return by doing a half shutter press, toggling ALT, or the script will automatically refresh after 3 seconds.

As usual I welcome any feedback on M3 Bracketing, especially from users of the script.

Tuesday, April 13, 2021

M3 Bracketing: fighting the Canon UI

As CHDK Lua or BASIC scripters will know, trying to maintain a clean UI, as you go in and out of ALT mode, and change the Canon interface, eg PLAY mode or display the Canon menus etc, is not a perfect science ;-)

In the latest version of M3 Bracketing, I've done the best I can to keep the M3 Bracketing and Canon UI synced, eg:

  • The script automatically senses the LCD or the EVF
  • Doesn't display the info bar in Canon PLAY mode
  • Shouldn't display the info bar in Canon MENU mode
  • Shouldn't be used with Canon histogram, ie you will get flashing, but is OK with the CHDK histogram

I personally switch off the single line console help, from the M3 Bracketing menu, but this option is down to the user. In assess mode, all the help line does is remind you about the buttons.

If the script is running and the bar 'disappears', then try one of the following:

  • Whether you are in ALT mode of not, pressing the ALT button on and off should recover the info bar
  • If in ALT mode, pressing the RIGHT button will recover the bar and carry out a reset, which is a necessary action if you change focal length and/or aperture etc
  • Switch between the LCD and the EVF, eg wave your hand in front of the EVF 

Also in the latest version I've split out the sky/infinity bracketing option into a new menu item, and added a check to warn you if you are requesting both exposure bracketing and a sky bracket: which you can't do ;-)

Remember the sky/infinity bracket feature works whatever you are doing, ie focus bracketing of taking an image at a single focus position.

As usual, I welcome any feedback from others using M3 Bracketing, especially ideas to make it better and/or more stable.

Monday, April 12, 2021

M3 Bracketing Update

Just a quick post to say I've tidied up the code in my M3 Bracketing script and added a new menu item:

#help = 0 "Console" {Off On}

The new menu items allows the user to switch the (single line) console on or off, to show M3 Bracketing help items. Once users are comfortable with using M3 Bracketing, they will likely switch this help off.

The  help field is only visible in the LCD, ie not the EVF.

As before, if the top info bar disappears, simply refocus in ALT or non-ALT mode. Alternatively press the RIGHT button in ALT mode.

You should do a RIGHT press, in ALT mode, after changing focal length or exposure, ie to reset M3 Bracketing.

I've now moved the focal length to the top info bar:

In the above we see the new layout in the top info bar, showing we are using a focal length of 14mm, we are focused at 710mm, the near DoF is at 480mm, the infinity blur is at 32um, and M3 Bracketing is telling us we will need to take at least 2 focus brackets to get to the hyperfocal.

In the above we see M3 Bracketing running in non ALT mode, where we can adjust the camera, look at the histogram and capture an image. Pressing the ALT button will return us to ALT mode, with M3 Bracketing still running and ready to carry out a focus bracket capture.

As usual I welcome any feedback on M3 Bracketing, or any of my posts.

Saturday, April 10, 2021

M3 Brackets: a change to the UI

This post is triggered by a few comments I got over on a DPReview forum. Namely, that I have been rather lax in my terminology and therefore some of my posts were confusing in places. Many thanks to those on the DPReview forum for pointing such things out to me.

In tweaking/correcting things, I've also taken the opportunity to change the M3 Brackets UI (see the screen shots and video below).

The latest version may be downloaded from the right.

So let's start with the (tidied up) Depth of Field Information Script (DOFIS) model, which is based on a split/thick lens model; that I believe, although not perfect, is a better model than assuming a thin lens.

The objective with the CHDK M3 Bracketing Lua script is to provide in-camera feedback, and carry out focus and exposure, auto bracketing, for deep focus photography, ie near to far/infinity in focus.

The script's first role is to help the user assess if focus objectives can be achieved in a single capture, ie focusing to ensure infinity and the nearest point of interest are in focus. I personally follow a simple strategy, namely: 'focus for the foreground and set (defocus) blur for the background'

Thus M3 Brackets is designed to tell you your point of focus, an estimate of the near depth of field (DoF) and the infinity blur in microns.

The absolute near DoF expression, ie as measured from the sensor plane can be found from the information in the DOFIS model above). Note the focus distance from the front principal, u, as used in the M3 Bracketing code, is s in the DOFIS model above:

Which, after manipulation, gives us this form of the expression for the near DoF, as measured from the sensor, that I use in the M3 Bracketing code:

Where f is the focal length, p is the pupil magnification, u the focus distance from the front principal, t the hiatus between the two lens principals, and h is the 'short form' of the hyperfocal distance, ie (f*f)/(N*C), where N is the infinity aperture number and C the circle of confusion or the blur criterion at infinity or at the overlap point when focus bracketing.

As for the UI change, because I'm a Magic Lantern user, I've put all the focus feedback into an 'info bar' at the top of the screen. This bar is accessible in CHDK ALT mode or outside of it. Thus you always will have information available.

In ALT mode, as before, you can initiate focus stacking by pressing the SET button. If you come out of ALT mode you can take images as normal, but still have real time access to the DoF info.

Whether you are in or outside of ALT mode, if the M3 info bar disappears then refocusing or pressing the RIGHT key in ALT or doing a half shutter press outside of ALT, will recover the bar.

M3 Bracketing will keep running until you do a full shutter press in ALT mode or capture a focus/exposure bracket set. When running, you can freely move in and out of CHDK ALT mode.

To show how M3 Brackets runs, the following screen captures and a video are illustrative. Note in the captures the CHDK overlays are skewed to the left relative to their actual position. Also note that peaking was fully functional as M3 Bracketing was running, although the HDMI capture, for some reason, doesn’t show the peaking.

In the above we see a typical M3 LCD view before CHDK is enabled. By repeatedly pressing the INFO button, we have arrived at the histogram screen. This is a good starting place to compose and set exposure. However, you should move away from this view before staring M3 Brackets, as the histogram will cause the screen to flash in ALT mode.

In the above we see CHDK has been enabled and that M3 Bracketing is ready to run, ie by doing a full shutter press.

In this screen capture we see M3 Bracketing is now running, as we see the console area, the single line of text above the CHDK ALT, is telling us that we are at a focal length of 12mm and that we have two options. If we change focal length we need to press the RIGHT button to reset M3 Bracketing. Or we could press SET to start a bracketing sequence, eg a focus bracket set or an exposure bracket set or a combined focus and exposure bracket set. 

We currently don't see the info bar at the top. So let's refocus.

Now we see the info bar, which has three areas of information. 

The left hand group of information tells us we are focused less than the hyperfocal (<H) and at 280mm from the sensor. M3 Bracketing uses the Canon lower focus value. 

The middle group tells us how many brackets we will take from the current focus position, when auto bracketing, to the hyperfocal. When auto bracketing the script will take at least this number of brackets plus one or two more, ie to cover to the infinity bracket position you have requested.

The right hand group shows the near depth of field from the sensor, 219mm in this case, and the infinity defocus blur in microns: 63um in this case.

In the above we see we have refocused to beyond the hyperfocal (194cm), where obviously the script is telling us the number of brackets is one. We also see that the near DoF is at 530mm and that we have a defocus infinity blur of 7um: a good place to be, ie better, than being at the hyperfocal, which, in this example, was based on a CoC/overlap blur of 20um.

In the above we see we have refocused and changed focal length, from 12mm to 22mm, and have thus reset things by pressing the RIGHT button. If we did not do a reset, the script would think we were still at 12mm.

In the above video clip we see M3 Bracketing running outside of ALT mode. In the console area, M3 Bracketing tells us the script is running, which is a useful reminder if the top bar should 'disappear' and needs refreshing with a refocus or a half shutter press. As we can see, the M3 Bracketing script is giving us real time access to the focus position, the number of brackets we will need, the near DoF and infinity blur.

In this mode it is easy to focus on a near object of interest, eg using peaking or zooming in, take note of it and then refocus for the background blur, checking to see if the near DoF covers the near field object we first focused on. If we have covered focus we can simply take as many shots as we like, after which we can return to ALT mode and carry on using M3 Bracketing. Or we could return to Alt mode without taking a shot and reset focus to carry out auto focus bracketing.

In the final video clip we see M3 Bracketing taking a focus bracket set, finishing with a focus bracket at three times the hyperfocal. Note the clip starts with me exiting M3 Bracketing and then restarting the script.

Once the script has taken a focus bracket set, or a full shutter has been pressed in ALT mode, the script will need to be restarted by doing a full shutter press in Alt mode.

Bottom line: if you have a Canon M3 and love deep focus photography, the M3 Bracketing script is well worth looking at: IMHO ;-)

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

Friday, April 9, 2021

M3 Brackets: tweaked to address CHDK integer math limitation

Just a quick update on my M3 Brackets script.

Up until now, some of the algorithms I have used in M3 Brackets were taken straight from my Magic Lantern DOFIS script.

When I originally did this, I thought I understood the CHDK environment's limitations, ie only integer maths is available, albeit augmented with the imath library functions. ML uses floating point maths.

When it comes to multiplying and dividing with the imath functions, all is OK. The problem I've just spotted, so shame on me for not seeing this earlier :-(, is when you need to do a square root, where you are limited to taking the sqrt of numbers less than 16384, or 16384'000 in imath parlance.

So I've now changed things to not use an imath.sqrt function and, hopefully, things are now well behaved. Plus, M3 Brackets now only runs with registered EF-M lenses.

I guess the lesson for coding is: test, retest and test again :-)

Thursday, April 8, 2021

M3 Brackets: Pupil Magnification Update

Assuming you have read the last post, you will know what this post is all about: namely adding pupil magnification to the M3 Bracketing script.

Rather than explicitly modelling pupil magnification, I've decided to 'exploit' pupil magnification as overlap focus insurance.

Without proof, the expression (in u space, ie from the front principal) for the next focus position is:

Where f is the focal length, p the pupil magnification and h is (f*f)/(Nc).

Following from the last post, M3 Brackets now includes a new menu item called

Assumed Pupil Mag

The thinking behind the new menu item is that it is easy to know if the lens you are using is of a retrofocus or telephoto design, by simply looking at the exit and entrance pupils (see the last post). Plus you can eyeball things to estimate the pupil magnification, ie without measuring anything.

As most deep focus bracketing will be undertaken with a retrofocus lens (telephoto focus bracketing will likely result in there being too many brackets), this post will only discuss that use case in detail. If your lens is telephoto and you still wish to use M3 Brackets to auto focus bracket, then set "Assumed Pupil Mag" to 1, where you are guaranteed to underestimate telephoto DoFs, ie achieve positive focus bracketing overlaps.

In the case of a retrofocus lens, we know that if we ignore the pupil magnification (p), we will over estimate the depth of field; which could result in focus gaps. 

As a reminder the following chart shows the amount we will over estimate if we ignore pupil magnification. Each contour is at 10% value, varying from 0 to 100% over/under estimate. The top part of the curve applies to retrofocus lenses (where we overestimate DoF by assuming a symmetric lens), the bottom to telephoto ones (where we underestimate DoF by assuming a symmetric lens). The chart also graphically shows a retrofocus lens is rather insensitive to pupil magnification at low image magnifications.

Let's now consider a real example, using the EF-M 11-22mm lens at 11mm.

If we 'eyeball' the lens the exit and entrance pupils are small! But the pupil mag looks to be about 4, ie the exit pupil diameter looks to be about four times the size of the entrance pupil. That is it’s a retrofocus lens.

To be sure, let's use an M3 Brackets value of 5 and enter this as our assumed pupil magnification. 

If we just look at pupil magnifications greater than 1, as we have a retrofocus lens, our plot now looks like this:

 Let's zoom in a bit:

The above tells us that, as the maximum magnification of the lens is 0.3, by assuming a pupil magnification of 5, if the actual p was 5, we would model the DoF correctly: obviously!

If, on the other hand, at the maximum object magnification the pupil magnification was only, say, 2, ie we were way off guesstimating p, we would be underestimating the DoF by just under 10%. Which is good when you are focus bracketing, where you are trying to not create focus gaps against your blur criterion. Nor do you wish to create large overlaps, which will increase the number of brackets you need to take.

As I don't wish to bore readers with more of the gory details, let's cut to the bottom line. When using M3 Brackets:

  • Check if your lens, at the focal length of interest, is of a retrofocus or telephoto design;
  • Estimate the pupil magnification by eye, eg 2 or 4 or 0.5;
  • If your estimate is less than 1, ie you are using a telephoto lens, then set M3 Brackets Assumed Pupil Mag to 1;
  • If your estimate is greater than 1, ie you are using a retrofocus lens, then set M3 Brackets Assumed Pupil Mag to slightly larger than what you think the pupil magnification is;
  • Set the overlap blur to a sensible number, eg 20 um;
  • Set the infinity blur value to, say, 3, ie we will take a final image at three times the hyperfocal, giving an infinity blur of 20/3, ie about 7 um.

Finally, as I've said before, M3 Brackets is ideally suited for wide angle lenses, eg the EF-M 11-22mm. Having said that, I've now added my other EF-M lenses to the pre-registered list, as you can use M3 Brackets outside of Alt mode to set focus on any registered lens:

  • EF-M11-22mm f/4-5.6 IS STM
  • EF-M28mm f/3.5 MACRO IS STM
  • EF-M55-200mm f/4.5-6.3 IS STM
  • EF-M18-55mm f/3.5-5.6 IS STM

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

Monday, April 5, 2021

Depth of field and exploiting your hidden friend

Advanced warning that this post is rather technical, but if you stick with it, you will hopefully increase your knowledge of depth of field, in a pragmatic way.

The title of the post is not that illuminating: who/what is my hidden friend?

The hidden friend in question is the lens pupil magnification, ie the ratio of the exit pupil diameter to the entrance pupil diameter.

This lens property remains hidden from us as most/all manufacturers do not publish the pupil magnification, even on a prime lens. Plus, with modern, non-prime, lens designs, the pupil magnification will vary and is not predictable in a linear way, unless you have a detailed model of the lens groups and how they move relative to each other.

For most/all photographers, lenses can be acceptably understood by asking the following questions:

  • Is the lens symmetric? That is the pupil magnification (p) is unity, with the exit pupil and entrance pupil diameters being the same;
  • Is the design representative of a retrofocus, with p > 1,  or telephoto, with p < 1, lens?

Every photographer can easily answer the above by simply holding their lens up to a light source and looking from the front of the lens, at the entrance pupil, or from the back of the lens, at exit pupil.

What you will see is one of the following views:

In the top image we are looking at a symmetric lens, ie the exit and entrance pupils are the same size, thus giving a pupil magnification of unity (1.0). In the second image we see the exit pupil, on the right, is smaller than the entrance pupil, so the lens is of a telephoto design, with a pupil magnification less than 1. Whereas in the third image we see the exit pupil is larger than the entrance pupil, so the lens must be of a retrofocus design, with a pupil magnification of greater than 1.

Many/most/all wide angle lenses are of a retrofocus design, whereas many/most/all long lenses are of a telephoto design. Lenses that are around 50mm tend to be symmeteric(ish). Prime lenses are fixed at one pupil magnification, whereas zooms will not have a single pupil magnification.

Now we know something about our hidden friend, ie the pupil magnification, let's now see why, for some photography, it may be useful to know the pupil magnification, or at least whether the lens is retrofocus or telephoto.

All of my depth of field and focus insights are pragmatically derived from my 'DOFIS model'. Note I said model, as we will 'never' know the actual lens design, nor do we wish to. 

Remember, all models are wrong, but some are useful.

Here is the DOFIS model as a reminder:

In the DOFIS model we ignore the actual lens design and make use of a split/thick lens representation of our lens, based on knowing the following five parameters:

  1. The focal length
  2. The maximum magnification at a particular focal length
  3. The minimum focus distance at a particular focal length
  4. The focus distance from the sensor
  5. The pupil magnification

The focal length and focus distance are easy to know/measure and we won't discuss these anymore. 

The maximum (image) magnification can simply be taken from the manufacturer's specifications or measured easily. Noting that for a zoom lens the maximum magnification will be stated at the longest focal length. Likewise the minimum focus at the maximum magnification can be taken from the manufacturer's specification or, once again, easily measured.

This leaves our hidden friend: the pupil magnification, which can be measured, but the question is: do we need to know its value?

To answer this we first need to be honest with ourselves. That is, answer the question: why do I need to know the depth of field?

Without listing every type of photography, I think it fair to say there are two extremes when it comes to depth of field considerations. 

There are those that are only interested in capturing a 'slice' of the image as being in focus, with an 'out of focus' background, albeit with the slice in focus potentially made up of multiple images to ensure the subject is addressed, eg as in macro photography. The extreme of this being a single capture, eg a non-macro portrait shot.

At the other extreme are those, such as myself, who are interested in capturing the entire scene in focus, from the nearest point of interest to infinity. Once again, the extremes here being a single image capture at or beyond the hyperfocal, to taking multiple focus brackets to cover the depth of field of the scene of interest.

To get some insight into our hidden friend, the pupil magnification, we can play around with the DOFIS model and rewrite the total depth of field in terms of the image magnification (m) and the pupil magnification (p): the expression being:

Where f is the focal length and c the circle of confusion criterion we are using, and n is the aperture number at infinity.

The usual caveats apply here, ie we are 'only' looking at defocus blur, ie ignoring diffraction blur, and assuming a perfect lens, ie ignoring all other aberrations.

In addition, let's simplify things even more by looking at the ratio of the depth of field ignoring the pupil magnification (assuming a symmetric lens) to using p, ie an asymmetric lens. Namely:

Resulting in our hidden friend's impact on DoF collapsing down to the following expression, which some will spot as ‘just’ the ratio of the two bellows factors:

We can now begin to see an important attribute of our hidden friend. Namely if we ignore pupil magnification then we will either under or over estimate the depth of field, according to whether we are using a telephoto or retrofocus class lens. 

As the equation may still not be that useful for some, let's look at a 3D graphical representation of the equation over a typical m/p space, eg m = 0 (ie at infinity) to 1 (ie macro), and p = 0.3 (ie telephoto) to 5 (ie highly retrofocus).

Here we see the impact of ignoring our hidden friend, the pupil magnification, ie assuming it is unity. Namely that with a retrofocus (wide angle with a p>1) lens, if we ignore the pupil magnification, we will over estimate the depth of field, with this becoming worse in the macro focus regime (m=1) and can be ignored at infinity focus (m=0). But, on a telephoto lens, ignoring the pupil magnification means that we are under estimating the depth of field.

The impact of ignoring the pupil magnification at the macro end (m=1), can be over 50%, ie for highly asymmetric lenses.

Before discussing this in a little more detail, let's collapse the above 3D plot to a contour plot, ie looking down on to the surface.

We can now clearly see that for symmetric lenses, ie p=1, we can ignore the impact of the pupil magnification: obviously!

On retrofocus lenses at low magnifications, ie less than say, 0.1, we can also ignore the pupil magnification's impact on depth of field. For example at p=5, the impact is ((1+0.1)5)/(0.1+5) = 1.08, ie less than 10%.

For telephoto lenses (p<1), if we do ignore the pupil magnification, the actual depth of field will always be more than we calculated, ie we will always under estimate DoFs on a telephoto lens by ignoring our friend. Thus we are less sensitive to ignoring p, assuming we are still interested in maximising DoF.

For retrofocus, wide angle lenses, the opposite is true. Namely, we will kid ourselves that we have a larger DoF than is the case, if we ignore our friend.

Let's now get to the bottom line: why do I keep calling the pupil magnification our hidden friend?

IMHO we can ignore pupil magnification for any single image capture. Having said this, now we understand the impact of the pupil magnification on our DoF, we can make pragmatic adjustments to our focusing, knowing if we are using a telephoto or retrofocus lens and assuming a particular DoF is important in our shot. 

Where knowing something about our hidden friend helps us, is when we are auto focus stacking with retrofocus lenses, for example using a Magic Lantern or CHDK Lua script to carry out a 'scape' focus bracket sequence. In such a case we don't want to create 'focus gaps': we need to ensure a focus overlap.

In the above, with infinity to the right, we see that the focus at Sn+1 is positioned to create a positive overlap between the last image's far DoF and the current image's near DoF.

We now can conclude with a few observations:

  • Pupil magnification does impact the DoFs of retrofocus and telephoto lenses when the magnification gets above about 0.1ish;
  • If we ignore pupil magnification, we will under or over estimate our DoFs, according to whether the lens is of a telephoto or retrofocus design;
  • The factor your depth of field will be adrift can be estimated from ((1+m)p)/(m+p);
  • For non-macro, deep focus bracketing (see previous posts on M3 Brackets and ML DOFIS scripts), it is useful to know that you can exploit the pupil magnification, without explicitly knowing it. That on a retrofocus lens simply guess/assume a pupil magnification to guarantee you don't create focus gaps in your focus stacks. For example, use a p of 3 or 5. On a telephoto use a p of unity to achieve focus overlap insurance.

In a future post I’ll discuss how I have used the above to create a 'focus insurance' feature in my CHDK M3 Brackets script.

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


For those interested in knowing where the 10% tolerability point exists, ie the DoF accounting for pupil magnification is only adrift from that ignoring it (p=1) by 10%, here are the curves for retrofocus and telephoto lenses:

Note the difference between telephoto and retrofocus.


Here is a more generalised plot showing the DoF % difference in ignoring pupil magnification, in 10% increments:

In the case of a retrofocus lens (top part of the plot), the plot shows that at a magnification of, say, 1, if you ignore the pupil magnification, your DoF estimate will be out, ie over estimated, by 50%, if your lens has a pupil magnification of 3.