General

<12345 ... 86>
General Discussions and Small Talk
Discussion Last answer Replies / Clicks
Rob Nagelhout

Section Critique - straight and tough

Hi friends and other members on FC, as you can see I upload my pictures in the section "Critique - straight and tough" to get serious critiques and tips to improve my work. In my humble opinion the way to do but also in that section the comment are very lovely. Some members have had critiques on my work and were afraid that it would get me angry. I've explained them that I appreciate honest critiques because I want to learn more from other photographers and then only compliments won't do. Now I hope more members will enter that section because critiques doesn't hurt. I hope to see many uploads in that section because for now I see 3 maybe 4 people in that part of FC. And don't get me wrong because it's not my intention to hurt somebody. I'm also willing to help when needed. So give it a try
gr.Rob
91 clicks
BrianTyler

Image Sharpness Problems

You can easily test your camera and lens for sharpness using a white piece of paper (use a good quality printer paper)
Draw a skinny line with a pencil on the paper.
Photograph it using normal day light, no flash.
Camera on a tripod, vibration reduction set to off.
Open the image using Imager.
I created Imager for my students and it can be downloaded from my web site for free.
http://www.MyCIGroup.com then navigate to Imager.
It is not great looking software but serves the purpose for research!
Open the image and save it to text file.
Open the text file using EXCEL.
Scroll down until you find the Grayscale section. For each pixel there is one number listed.
Find the transition from white to black. It should look something like 175 175 175 70 60 55 55 55 55
This may vary in numbers, which is not important. It all depends on how white the paper is and how dark the line is.
Again, this is not important.
Count the number of pixels it took to transition from white to black. In my example above it took 3 pixels.
This transition is what humans interpret as sharpness or in focus. If it takes 5, 6, 7 pixels to transition, then the image is less sharp. Measure it.
Repeat the test by taking the camera out of autofocus, change aperture, etc. You will soon understand your camera.
A standard 35 mm camera will not transition in 1 pixel, it should be 2 to 3 pixels.

A couple of things to consider, keep the distance just far enough to allow the camera to focus properly. I would say 6 feet. Experiment with zoom settings but don't try to macro the object. That defeats the purpose of the test.
08.05.15, 04:42
You can easily test your camera and lens for sharpness using a white piece of paper (use a good quality printer paper)
Draw a skinny line with a pencil on the paper.
Photograph it using normal day light, no flash.
Camera on a tripod, vibration reduction set to off.
Open the image using Imager.
I created Imager for my students and it can be downloaded from my web site for free.
http://www.MyCIGroup.com then navigate to Imager.
It is not great looking software but serves the purpose for research!
Open the image and save it to text file.
Open the text file using EXCEL.
Scroll down until you find the Grayscale section. For each pixel there is one number listed.
Find the transition from white to black. It should look something like 175 175 175 70 60 55 55 55 55
This may vary in numbers, which is not important. It all depends on how white the paper is and how dark the line is.
Again, this is not important.
Count the number of pixels it took to transition from white to black. In my example above it took 3 pixels.
This transition is what humans interpret as sharpness or in focus. If it takes 5, 6, 7 pixels to transition, then the image is less sharp. Measure it.
Repeat the test by taking the camera out of autofocus, change aperture, etc. You will soon understand your camera.
A standard 35 mm camera will not transition in 1 pixel, it should be 2 to 3 pixels.

A couple of things to consider, keep the distance just far enough to allow the camera to focus properly. I would say 6 feet. Experiment with zoom settings but don't try to macro the object. That defeats the purpose of the test.
283 clicks
To the
top