Lighting Basics

I'm typing this for my own reference.
Still trying to get correct settings for white balance.
I hope that this will also help others who wish to have a quick reference on improving the quality of photo taking, especially if in indoor.

Tungsten (2500K - 3500K) - The bulb sign. For slightly bluish lighting.
Fluorescent (4000K - 5000K) - The tube sign. for slightly yellow lighting
Daylight (5000K - 6500K) - The sun sign. Used when outdoor w/o shade.
Using Add-on flash (5000K - 5500K) - The lighting sign. Used usually when indoor.
Cloudy (6500K - 8000K) - The cloud sign. For medium overcast sky.
Shade (9000K - 10000K)- The house sign. For heavy overcast sky or shade.

If the photo still appear too cool or warm on the LCF screen preview, can try to increase or decrease the colour temperature. This should balance it up a little.

Sometime the camera maybe 'off' in its auto WB mode. The camera might be more effective if it can detect something that is white or bright colorless object to use as a refernce. Or if we have multiple light source, the camera may do a 'averaging' of all lightings which may not be what we want.

We can however try the manual WB to capture a more realistic result.

Deciphering second field in shadow file in RHEL

The second field in shadow file contains encrypted password as well as other information. The file is readable by root only and the fields include the following:

1) username (usually up to 8 characters and case sensitive. Direct match to /etc/passwd)

2) encrypted password (13 characters)

3) The number of days since 1st Jan 1970 since the password has been last changed.

4) The number of days before password may be changed. If you see a '0', you can change any time.

5) The number of days after which the password must be changed. If you see 99999, no change is needed forever.

6) The number of days before to warn user of an imminent password expiry.

7) The number of days after password expiry that the account is disabled.

8) The number of days since 1st Jan 1970 that this account is disabled.

9) Last field is reserved. Not used at this moment.

More details on how to read the 2nd field?

- If you have blank entry, though is a bad idea but this mean that you do not need password to log in.

- If you have a '*' entry, this means the account is disabled. User cannot log in.

- If you have a '!' entry, this means the account is disabled as well. Use cannot log in.

- if you have a "!!" entry, this mean the account has never been used yet. User has not log in before and cannot log in.