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January 7, 2010
Photoshop tips – avoiding moiré when resizing
When you resize an image with repetitive patterns, you stand the chance that the pattern itself will form another pattern. This is called moiré. When I resized this image for web display, I had to take care to make sure the blue window shutters didn’t generate a moiré pattern.
Here is the full image resized for web. The image here is 600 pixels wide.
Click on the photo to see the image as a 900 pixel wide image.
By going from the original 12 megapizel image (4288 pixels wide), directly down to 600 pixels in a single adjustment ..
.. I get an image where the detail looks like this:
You can see the moiré pattern there in the blue window blinds as a diagonal shaded pattern. You run the risk of this happening if you do a massive jump in resizing in one go.
But by doing the resizing as 10% reduction steps, you can most often avoid that. Here is how it looks when resized as a sequence of resizing steps:
Instead of changing the pixel dimension from 4288 pixels right down to 600 pixels wide, instead do it as approximately 10% jumps in size. You would now change from 4288 pixels (as an example), 3900 pixels wide. And from there you would change to 3500 pixels, all the way down to the size you want your image to be. The diagonal moiré pattern has now been nearly completely eliminated.
Sharpening an image (as you have to when you resize an image for web use), also enhances the pattern. Therefore, with this image, I removed the sharpening for the window shutters to further reduce the effect.
Of course, doing this kind of step-by-step resizing, is best done as an action. You can create your own, or use one of the many available on the internet. The best actions also provide some sharpening as an intermediate step for best results.
A little bit about the post-processing of the image …
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Comments (15)
January 4, 2010
combining flash and ambient light
Going by the emails that I receive, one of the areas that many photographers struggle with is that of combining ambient exposure and flash exposure. This question is also expressed in other ways. It can be a frustrated, “where do we even start?” I also often see it expressed as an involved step-by-step deconstruction of technique, making the entire process more complex than it is.
In reply to that, and many other emails I’ve received in the past few months, I’d like to offer an analysis of a few images from a recent shoot.
[ click on the photo for a larger image ]
One of my favorite clients has the most adorable baby boy that she wanted some portraits of. I had to shoot fast, since his attention span was .. oh, zero. He’s still a baby! I also wanted to be able to cover myself in getting some available-light only portraits, and some with bounce flash. I didn’t want the flash to be overwhelmingly bright. And in bouncing the flash, there was also less chance of disturbing the baby. So I had to mix it up in order to get some variety, and be sure of images that worked.
The image at the top was shot with the Nikon D3 and the Nikon 70-200mm f2.8 AF-S
Lighting here was a combination of available light and bounce flash. And as usual, I used the black foamie thing to flag the flash so NO light from the flashgun fell directly on the child.
My camera settings: 1/100 @ f4.5 @ 640 ISO, using TTL flash
The FEC was not recorded, but would’ve been around 0EV because my flash isn’t merely fill-flash here, but fairly dominant.
Now where the settings look like they might be informative, I also often feel that these numerical values are a diversion. Too many photographers will get hooked on the choice of f4.5 over another aperture. Whey 1/100th of a second? Why 640 ISO?
The truth is that this could’ve been a different combination of settings. What is important here, is the quality of light. It is our major concern here, and should interest us more than f4.5 at this moment.
The light on the baby’s face is directional. There is more light coming from camera left .. and from this you should be able to deduce that I did indeed bounce my flash to my left. Using that piece of black foam to flag my flash, I was able to get directional light like that.
The light is soft. Since I bounced my flash into the room, and it bounced off the walls, and furniture, I will have soft light.
So those two aspects of the light from my flash is easily understood – soft directional light.
Now let’s look at how I chose to balance my flash with the available light …
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Comments (46)
January 1, 2010
I want to thank all the readers of the Tangents blog, and everyone who has contributed to this site – whether in asking questions, or posting their suggestions and help, or adding new material. A sincere thank you to everyone who has passed the site on to friends and colleagues, and a big thank you to everyone who has linked to my site on the photography forums.
That’s my Google analytics Map Overlay for the past 3 months .. a quarter million visits from across the world! Russia, Indonesia, Nepal, Finland, Algeria, Iceland, Chile, Morocco, Poland, Germany, Turkey, Italy, Netherlands, UK, Ireland, and of course my home country South Africa, and where I now live, the USA. 176 Countries across the world!
I changed the website into the current blog format in May 2007. Before that, it was a mish-mash of a few web pages. Since I changed it to a more easily maintained blog format in 2007, traffic has steadily increased. In fact, at the start of 2009, Alexa ranked the planetneil site at 220,000 of all the websites in the world. Right now the planetneil site is hovering around the 150,000 mark. That’s a big jump in just this past year!
I get many notes from people telling me this website has had a huge impact on their photography, and it always feels good to hear that. It’s an incredible feeling knowing that I have been able to help someone in understanding something, or improving their photography, whether personally or professionally.
Now, I just need to get my email inbox down to zero! There are so many emails that I haven’t been able to get to in the past few months with the usual August – November crunch period. I’ll do my best to get to them all. Keep checking in!
With all this, my own understanding of photography, and my experience and skills have grown too over this time. In a way this website has been an unfolding of that as I learn.
So, from me, to everyone across the world, thank you … and here’s to a wonderful 2010 ahead.
Filed under: news — Neil vN @ 9:30 pm
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