Recently we ended up with a Maya scene with locked, read-only, nodes which prohibited us from deleting them from the scene. This usually happens to nodes having been part of a locked reference which has been imported into the scene. In our case, we had no access to the original referenced file, so we had to unlock these nodes from being read-only.

For some reason it didn’t work to unlock them using the lockNode command from within Maya and I had to write a Python script which would read each line of the Maya ASCII file and strip out any lines containing “lockNode”.

This is the script, which I’ve saved as unlock.py in the same directory as the scene file:

import re

infile = open('original_file.ma', 'r')
outfile = open('new_file.ma', 'w')

for line in infile:
	lockNodeFound = False
	for word in re.findall(r"\w+", line):
		if (word == 'lockNode'):
			lockNodeFound = True
	if (lockNodeFound):
		#print 'Line removed: ' + line
		pass
	else:
		outfile.write(line)

Switch out the file name "original_file.ma" to match the name of your file. Back up your original Maya scene file somewhere safe and run the script in a command line window (not inside of Maya) like this:

python unlock.py

Although a new file is created, I take no responsibility for how you use this script, of course. You’re on your own :)

If you want visual feedback of what’s going on, just uncomment the line that says #print 'Line removed: ' + line but this will make large scenes take significantly longer to process.

Let me know if this helps in the comments section below.

Fixing “Read-only” nodes in Maya

This simple python script looks for the latest file with .ma file extension in the path given and prompts the user whether to load it or not. Just verify that the searchDir variable is pointing to your temp dir.

import os, glob, time
import maya.cmds as cmds

def crashFileLoader():
    searchDir = os.environ['TEMP'] + '/'
    files = filter(os.path.isfile, glob.glob(searchDir + '*.ma'))
    files.sort(key=lambda x: os.path.getmtime(x))
    latestCrashFile = (str(files[len(files)-1]))
    timeStamp = "%s" % time.ctime(os.path.getctime(latestCrashFile))
    
    messageString = 'Are you sure you want to open ' + latestCrashFile + ' created on ' + timeStamp + '?'
    retVal = cmds.confirmDialog( title='Confirm', message=messageString, button=['Yes','No'], defaultButton='Yes', cancelButton='No', dismissString='No' )
    
    if retVal == 'Yes':
        cmds.file(latestCrashFile, force=True, open=True)

Launch the script with:

crashFileLoader()

Load latest Maya crash file

In The Foundry’s Nuke, accessing the metadata of an image sequence’s Read node can be done via the ViewMetaData node. But if you wish to extract values out of the metadata and e.g. burn the timestamp for each frame into a render, it is actually easier to just do some python scripting.

Read More

Metadata and EXIF in Nuke

Fujifilm Finepix X100 – LCD/EVF observations

Some people have asked whether the “Preview Depth of Field” function is different from the regular LCD/EVF view or not (which it is), why the histogram is acting up (which it sometimes can do) and I’ve also seen questions regarding why exposure lock (AE-L) mapped to the AFL/AEL-button does not seem to be happening when pressing the AFL/AEL-button. Here’s an attempt to try and explain why this is so.

Below, the two stages of what the LCD/EVF will show when shooting a picture, explained.

1. Just looking through the EVF or on the LCD

When looking through the EVF or on the LCD, without pressing any buttons, the camera will automatically set its own aperture value for the LCD/EVF view (and therefore also DOF and exposure). It does this in order to create a good visual representation to show what is in frame, regardless of what the physical dials on the camera are set to.

This does in no way alter your choice of aperture, shutter speed, ISO etc for the photo you are about to take. But in short, framing is the only thing you can really trust at this point.

I believe that the image shown in the LCD/EVF here is a good representation of what the camera would record if set to P mode (fully automatic).

Unfortunately, the luminance histogram in the LCD/EVF seem to be based on these arbitrary settings in real-time which actually renders it unreliable in some cases. When in A mode (aperture priority), S mode (shutter priority) or P mode (program AE, fully automatic), the histogram is somewhat accurate, as the camera will strive to achieve the exposure portrayed in the LCD/EVF. But whenever you are shooting in M mode (manual exposure) you never know if your luminance histogram is even close and you might as well just shoot an image and check the luminance histogram in the playback mode. Because of this behaviour, this leads me to believe that in the OVF, the histogram is based off the very same arbitrary values that the camera has chosen, being just as unreliable (again, especially in M mode).

As the OVF power saving feature of the X100 disables the histogram, it would make sense that the X100 would indeed save a lot of power by not having to calculate the histogram based off the arbitrary values recorded, processed (but not shown unless in LCD/EVF) when using the OVF. However, I would not recommend using the OVF power saving feature for this particular reason as it also slows down auto focus.

2. Half-pressing the shutter button

When half-pressing the shutter button, evaluations are being made and additional preview features will kick in such as an aperture preview, not necessarily according to the physical aperture dial setting. This means the DOF here is, again, a preview. The focus is locked. Also, the exposure preview in the LCD/EVF will be locked. The actual exposure (which is not the same as the exposure preview), will also be locked (if not in M mode), and this may or may not be accurately portrayed in the exposure preview (more on this further below).

Now, regarding the exposure preview: If there’s plenty of light, the exposure is mostly quite accurately portrayed in the preview, but it’s when you stop down the lens to f/11 or f/16 in dim-lit situations when the exposure preview function will most likely be way off. Then the LCD/EVF preview can show you a bright image and as you fully press the shutter to take the photo, the photo comes out all black. Just set the camera to f/16 and at a shutter speed of 1/4000 and see for yourself if the half-press preview matches the actual photo taken when in dim-lit indoor situations.

“Preview Depth of Field” vs regular LCD/EVF view

Since you cannot change aperture and actually see live updates of this in the LCD/EVF, Fujifilm has created the “Preview Depth of Field” function. It will stop down the lens accordingly in the LCD/EVF as you move up the aperture values and should give you a much better idea of what the DOF will be like compared to the regular LCD/EVF view (which, explained above, uses an arbitrary aperture value chosen by the camera to minimize video noise etc).

This feature does not take shutter speed or ISO into account, and will show you the DOF preview at a shutter speed as well as ISO chosen by the camera. Therefore, all you really get a preview of here is the DOF.

Exposure lock (AE-L) with the AFL/AEL-button

Setting the AFL/AEL-button to lock exposure only (AE-L) does indeed perform the actual exposure lock when pressed, but only in A or P mode (AE-L is useless in M mode). Not until you half-press the shutter you will see an exposure preview of this in the LCD/EVF.

Do note that in manual focusing mode (MF) the AFL/AEL-button serves as a single AF-run initiator and overrides any assignment to this button. Therefore having AE-L or AF-L assigned to the AFL/AEL-button during MF does not lock anything. This however, can be seen as a strength. Use the manual focusing ring or the AFL/AEL-button to find focus, half-press the shutter to lock exposure and finally shoot the picture.

Other X100 resources

Make sure to check out some of my other X100 articles: