ND Simulation Helper Script

Started by garry23, April 17, 2018, 10:44:54 PM

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garry23

This thread is superseded by https://www.magiclantern.fm/forum/index.php?topic=25731.0

Whenever we wish to take a Long Exposure (LE) image, we would ideally fit an ND filter that allowed us to capture the best image, eg continuing to control DoF, ie with aperture, and select the time required, ie for the effect we were looking to create.

I wrote this script for those occasions where you don't have the 'right' ND filter.

This version of the script was explicitly written for my 5D3, ie button locations and availability: but any competent Lua scripter will be able to recode to suit their needs. Also I have annotated the script with comments and highlighted hooks, eg where you can insert your own controls, eg to switch off one of your scripts that might conflict with the ND script.

I personally use the script with my Focus Bar script, and have 'deconflicted' the two, ie if the ND script is running, it will switch off the FB script. I also have allocated the script to my C3 custom mode.

With the script off, my screen looks like this:





Here we see the FB script running, with ML telling me (bottom left) I'm running in C3 config mode.

To switch the ND script on simply press RATE (which is 100% hijacked by the script, but personally I never use the RATE key). The screen will now switch to look something like this:





Here we see the script is showing that we are requesting 10 images and, of course, at a shutter of 1/4s this equates to 2.5s. The green text tells you that if you use the MENU and INFO keys you will be adjusting, down and up, the number of brackets (images) to take.

Normal access to the MENU and INFO keys is achieved by switching off the ND script, ie pressing RATE.

If you press the ZOOM key when the script is running, the screen looks like this:





This shows that, in addition to the 10 images, I am now requesting a 5s delay between images. This delay allows you to carry out 'people removal' bracketing, ie through post processing using Photoshop statistics. Once again you can use MENU and INFO to adjust the time delay.

The scripts main menu looks like this:





The ND only option shown means that only the requested images will be taken. The other option is ND+. In this case the script will take an ML advanced bracket sequence after the other images have been captured. Thus in post you will have a near perfect bracket set: the ND brackets that will be combined using the smart object stack mode technique and the exposure set, that you can blend in.

The first image delay is either 0, 2 or 5s. So switch of Canon delays.

The User feedback is off, audio, led or both. This is useful to help in tracking the script's start, which is achieved via a long (5s+) press of the SET button.

The Additional menu looks like this:





The bookmark is either NO or YES. YES will place a dark frame at the start and end of the capture sequence: to help differentiate a sequence in post.

Shadow SNR is a control variable that is between 0, 2, 4 or 6Ev and controls the ETTR shadow end. Use this to ensure the advanced bracketing starts at a shadow exposure that is 'brighter' than if the value was 0. The ETTL Set Time is there to help ensure the ETTR finds a solution.

The script will remember the top menu's state, but not the additional menu.

I'll be releasing the script on my blog at photography.grayheron.net and will write about post processing. But for now I'm giving ML friends early access to the script at: https://gist.github.com/pigeonhill/17b0101b99af0ad99b1032486a340f87

As usual I welcome all feedback.

garry23

...as promised a post on the new script: http://photography.grayheron.net/2018/04/neutral-density-filter-simulation.html

BTW here is how I use the script. I had an ND filter with me to 'only' capture a 5s image, but wanted something more like 60s. So I asked the script to grab 12 images. A little bit of post processing in PS (see post) and the before (5s) and after (60s) images look like this:








garry23


sys73r

this is really cool! I'm trying it out. thanks for sharing it.

garry23

@sys73r

Pleased to share, but remember I write my scripts for my workflow ;-)

Let me know how you get on and if I can make the script better.

Cheers

Garry