Category Archives: Technology

Understanding AF Detection at f/8 on DSLR Cameras

Misunderstanding 1: The inability to focus at small apertures is nothing to do with amount of light. You still have a lot of light with f/8 in sunny day, much more than at f/2.8 indoors. It is actually related to Phase Detection AF mechanism which operates much like range finder comparing images from different angles to determine it’s in-focus or not. Small lens aperture just blocks light paths from different angles, and as the result, makes AF sensor unable to work reliably or not at all.

Misunderstanding 2: Older Nikon cameras may not auto-focus reliably with a lens having a maximum aperture smaller than f/5.6. That may sound bad, if you assume that it means the camera will not auto-focus reliably when the aperture is closed down to f/5.6. That is not what Nikon is saying! Instead they are telling us that auto-focus may not work reliably on older Nikon cameras with a lens having a maximum aperture of f/5.6, with the emphasis on the word maximum.

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D750 vs D810 vs D5 vs D850 vs 5D mark IV


Parameter D750 D810 D5 D850 5D Mark IV
Introduce Year 2014/09 2014/06 2016/01 2017/09 2016/08
Sensor Resolution 24.3 MP 36.3 MP 20.8 MP 45.7 MP 30.4 MP
ISO Score by DxOmark 2956 2853 2434 ???? 2993
Low Pass Filter Yes No   No Yes
Buffer size (RAW 14 bit) 15 28 200 51 21
Storage Media 2x SD 1x CF, 1x SD 2x XQD or 2x CF 1x QXD, 1x SD (UHS-II) 1x CF, 1x SD (UHS-I)
Continuous Shooting Speed 6.5 FPS 5 FPS 12 FPS 7.0 fps 7.0 fps
Exposure Metering Sensor 91,000-pixel RGB sensor 3D Color Matrix Metering III 91,000-pixel RGB sensor 3D Color Matrix Metering III 180,000-pixel RGB sensor 3D Color Matrix Metering III 181,000-pixel RGB sensor 150,000-pixel RGB+IR metering sensor
Autofocus System Advanced Multi-CAM 3500FX II Advanced Multi-CAM 3500FX   Multi-CAM 20K  
Dedicate AF Engine No No Yes Yes  
Number of AF Points 51 AF points, 15 cross-type 51 AF points, 15 cross-type 153 AF points, 99 cross-type 153 AF points, 99 cross-type 61 AF points, 41 cross-type
Detection Range -3 to +19 EV -2 to +19 EV -4 to +20 EV -4 to +20 EV -3 to +18 EV
AF Detection Up to f/8 (11 AF points) Up to f/8 (11 AF points)   Up to f/8, 15 sensors  
LCD Size and Type 3.2″ TFT-LCD Tilting 3.2″ TFT-LCD 3.2″ Touchscreen TFT-LCD 3.2″ Tilting + Touchscreen LCD 3.2″ Touchscreen LCD
Dual Pixel AF       No Yes
Dual Pixel RAW       No Yes
Built-in GPS No No No No Yes
Battery EN-EL15 EN-EL15 EN-EL18a EN-EL15a  
Battery Life 1,230 shots (CIPA) 1200 shots (CIPA) 3,780 shots (CIPA) 1840 shots (CIPA) 900 shots (CIPA)
Battery Charger MH-25a Quick Charger MH-25a Quick Charger   MH-25a Quick Charger  
USB Version 3 3 3 3 3
Weight (Body Only) 26.5 oz. (750g) 31.1 oz. (880g) 1,405g (With Battery + 2x XQD) 915g 800g
MSRP Price $2,299 (as introduced) $3,299 (as introduced) $6,499 $3,299 (as introduced) $3,499 (as introduced)


Nikon D850 vs Canon 5D Mark IV Specification Comparison


Camera Feature Nikon D850 Canon 5D Mark IV Comparison Notes
Sensor Resolution 45.7 MP 30.4 MP More pixel for wildlife & landscape photography  
Sensor Type BSI CMOS CMOS Better ISO (35xx vs 2993 DxO Score) Not yet known the ISO score but Sony BSI CMOS is well-known for low light (as of A7Rii)
Low-Pass Filter No Yes No AA filter brings more sharpness, but may result in moiré issue in bird photography Some claims that moiré issue is not significant
Buffer: RAW 14-bit Lossless Compressed 51 21    
Storage Media 1x QXD, 1x SD (UHS-II) 1x CF, 1x SD (UHS-I)    
Continuous Shooting Speed 7.0 fps, 9.0 fps with MB-D18 7.0 fps    
Number of AF Points 153 AF points, 99 cross-type 61 AF points, 41 cross-type   Some point out that 5D mark IV actually has more working cross AF points at aperture F/8
AF Detection Range -4 to +20 EV -3 to +18 EV -4 mean better  focus in low light  
Auto AF Fine-Tune Yes No    
Focus Peaking Yes No    
Focus Stacking Yes No    
Video Maximum Resolution 3,840 x 2,160 (4K) @ up to 30 fps 4,096 x 2,160 (4K) @ up to 30 fps    
Video Crop Factor 1.0x 1.74x    
LCD Size and Type 3.2″ Tilting Touchscreen LCD 3.2″ Touchscreen LCD Tilt LCD gives more flexible to shoot from different angles Less practical if AF is not good in live view
Dual Pixel AF No Yes Much better focus ability with Live View and for Video Nikon has contrast AF only when using live view, which is very slow.
Dual Pixel RAW No Yes    
LCD Resolution 2,359,000 dots 1,620,000 dots    
Built-in GPS No Yes GPS-enabled is good for wildlife photography  
Bluetooth Yes No    
Battery Life 1840 shots (CIPA) 900 shots (CIPA) Longer is better, but 900 is good enough.  
Button Illumination Yes No    
Weight (Body Only) 915g 800g    
Dimensions 146.0 x 124.0 x 78.5mm 150.7 x 116.4 x 75.9mm    
MSRP Price $3,299 (as introduced) $3,499 (as introduced) Canon 5D4: 65tr

Nikon D850: ??

(Table content: courtesy




Change default Backup folder of iTunes in Windows 7/8/10

Change default Backup folder of iTunes in Windows 7/8/10:

  • Delete all backup file at C:\Users\___XXXUserNameXXX___\AppData\Roaming\Apple Computer\MobileSync\Backup
  • Delete Backup folder at C:\Users\___XXXUserNameXXX___\AppData\Roaming\Apple Computer\MobileSync\
  • Create a new backup folder: (e.g. D:\RunApp\iTunes\MobileSync\Backup)
  • Run cmd (command promt)
  • Create/Link current iTunes backup folder to the newly created folder by running the below command:
  • mklink /J “C:\Users\___XXXUserNameXXX___\AppData\Roaming\Apple Computer\MobileSync\Backup” “D:\RunApp\iTunes\MobileSync\Backup”
  • Now all backup files will be save into D:\RunApp\iTunes\MobileSync\Backup

Install Ubuntu 16.04, CUDA 8.0 and EwbfMiner for zCash mining with nVidia GPU


// Install Ubuntu Server 16.04.2

// On OK go next

// Set static IP by editing: /etc/network/interfaces

$ cd /etc/network

$ sudo nano interfaces

// Change from:

auto lo

iface lo inet loopback


auto enp2s0f0 (name of interface)

iface enp2s0f0 inet dpch

// Change to:

auto lo

iface lo inet loopback


auto enp2s0f0 (name of interface)

iface enp2s0f0 inet statis





// Save and exit.


// Change default SSH port:

$ cd /etc/ssh

$ sudo nano sshd_config

// Change Port 22 into Custom Port.

// OK: now the server can be access remotely by SSH at

// Reboot server (for static IP get effect):

$ sudo nano reboot


// Install CUDA to support nvidia graphic cards

// Instruction (

// Verify You Have a CUDA-Capable GPU

$ lspci | grep -i nvidia

// Verify the system has gcc installed

$ gcc –version

// If not installed yet. Then install it:

$ sudo apt install gcc

// ok with gcc 5.4.0

// Verify the system has the correct Kernel Headers and Development Packages installed

$ uname -r

// (if not installed) The kernel headers and development packages for the currently running kernel can be installed with:

$ sudo apt-get install linux-headers-$(uname -r)


// Now download cuda at –> Menu: Linux > x86_64 > Ubuntu > 16.04 > deb (local)

$ mkdir apps && cd apps

$ wget

// Install repository meta-data (unpack):

$ sudo dpkg -i cuda-repo-ubuntu1604-8-0-local-ga2_8.0.61-1_amd64-deb

// Update the Apt repository cache

$ sudo apt-get update

// Install CUDA

$ sudo apt-get install cuda

// on ok go next


// Post CUDA installation actions:

// Environment Setup (must do)

$ sudo nano .profile

// The PATH variable needs to include /usr/local/cuda-8.0/bin

// To add this path to the PATH variable in .profile:





// OK


// To install the Display Driver, the Nouveau drivers must first be disabled.

// Create a file at /etc/modprobe.d/blacklist-nouveau.conf with the following contents:

$ cd /etc/modprobe.d

$ sudo nano blacklist-nouveau.conf

// Add 2 below lines:

blacklist nouveau

options nouveau modeset=0

// Save and exit file editing.


// Install nVidia Toolkit and Drivers

$ sudo apt install nvidia-cuda-toolkit

// Check if driver of nvidia GPU is installed correctly:

$ nvidia-smi

// OK


// Install ewbfminer:

// Source:

$ mkdir ewbfminer && cd ewbfminer

$ wget

// Unzip and Install downloaded file in ewbfminer folder:

$ tar -xzf Zec.miner.0.3.4b.Linux.Bin.tar.gz

// Config ewbfminer in miner.cfg

$ sudo nano miner.cfg

# main server



port   4444

user   xxxUser.worker

pass   password


#additional server 1



port   3357

user   xxxAddress.worker

pass   password

// Config to include only below line:

$ sudo nano

./miner –config miner.cfg

// Save and exit

// OK


// Run ewbfminer:

$ cd apps/ewbfminer

$ ./

// Run ewbfminer inside screen session to allow closing current ssh terminal:

$ screen

$ cd apps/ewbfminer

$ ./

$ Ctrl-A   -then-  d  (to exit ‘screen’ session)

// Close ssh terminal



Screen – terminal multiplexer in Ubuntu Server



Screen is a terminal multiplexer, which allows a user to access multiple separate terminal sessions inside a single terminal window or remote terminal session (such as when using SSH).



The screen package can be installed on Ubuntu using any method.

Starting with the Jaunty release, the screen-profiles package (later renamed Byobu) provides advanced features such as status bars, clocks, and notifiers. The package can also be manually installed on previous Ubuntu releases.



Screen can be started by typing



in a terminal. Press Enter after reading the introductory text.

Virtual terminals in Screen can be manipulated by pressing the Ctrl+A key combination, and subsequently pressing a key to execute one of the commands given below:

  • c creates a new virtual console

  • n switches to the next available virtual console

  • p switches back to the previous virtual console

  •  lists all available virtual consoles and their assigned numbers

  • hitting a number key brings the corresponding virtual console to the foreground
  • Esc lets you scroll back and forth in your terminal output

  • d detatches the current screen sessions and brings you back to the normal terminal

When a Screen session is detached, the processes that were running inside it aren’t stopped. You can re-attach a detached session by typing

screen -r


in a terminal

To remove the annoying copyright notice at startup, edit your /etc/screenrc with

sudo nano /etc/screenrc


and remove the hash which begins the line

#startup_message off


Save the file, and you will not see it again.

For further information and more advanced commands, you can refer to the screen man page. Source:

Install and Run Bitcoin Core and Wallet in Ubuntu Server 16.04

  1. Install Bitcoin Core:
    • $ sudo apt-add-repository ppa:bitcoin/bitcoin
    • $ sudo apt-get update
    • $ sudo apt-get install bitcoind
  2. Run Bitcoin Node:
  3. Optional: start Bitcoin node at boot:
    • Run the following command to edit your crontab:
      • $ crontab -e
    • Scroll to the bottom of the file displayed and add the following line:
      • @reboot bitcoind -daemon
    • Save the file and exit.
  4. Verify if Bitcoin node is running:
    • $ bitcoin-cli getinfo
  5. Stop Bitcoin Core/Node process:
    • $ bitcoin-cli stop
  6. Create a new wallet address:
    • $ bitcoin-cli getnewaddress               # create an address in default account
    • $ bitcoin-cli getnewaddress “John”   # create an address in John account
    • (understanding account in wallet)
  7. Show current wallet addresses:
    • $ bitcoin-cli listreceivedbyaddress 0 true      # show all address from all accounts
    • $ bitcoin-cli getaddressesbyaccount “”     # show address in default account
    • $ bitcoin-cli getaddressesbyaccount “John”   # # show address in John account