Aperture | Time and Time Photographer

Aug22 1

The Photography Tip of the Week #075

Posted by Philip in Photo Philosophy, Photo Technique, Podcast

That’s a Sweet Brick Wall

There are many things in life that have a sweet spot and photography is no exception. For this tip I’m interested in the sweet spot of your lens, specifically which aperture is the sharpest all around. It’s a very simple test and only requires a few minutes with each lens you want to test. I call this the brick wall test. You don’t have to use a brick wall, as long as you use something that has lots of detail. Some people will put a newspaper on the wall, but I prefer to do this outside and newspaper blows around very easily. So here’s my setup:

Use a tripod about 10 feet or 3 meters away from the wall, because you want all of your images to be almost exactly the same.
Set ISO to 100 or 200 and shoot during a sunny day.
Aperture priority mode. Shutter speed doesn’t affect your sweet spot. You will start with either your largest or smallest aperture and photograph the exact same image on each aperture setting.
Autofocus. It shouldn’t matter how the focus is set since you aren’t moving the camera, but if you must set it, just center focus will be fine.
Using a cable release would be nice, but not overly necessary.

Once you’ve made all your images, load them up in a program where you can look at the centers of each image at 100%. This becomes a value judgment on your part. Cycle through the images until you determine which one is the sharpest. Since you have locked down most all the variables and the only variation is the aperture you should be able to determine which f-stop is the sweet spot.

Here’s the images of various apertures side by side from my test. As you can see they could all be the same image. There is very little difference in coloring and overall look. You can be fairly certain that the only measurable difference now is just the aperture.

Now let’s look at a section of the images at 100%. You can see that f8.0 is noticeably sharper than either f4.5 or f22. I’ve scrutinized over all my aperture settings for this lens and know that f8.0 is the sharpest or the sweet spot.

With this knowledge you now know that if you want to get sharper images, you will want to get that aperture as close to your sweet spot as possible and adjust your other settings to match.

Aug08 0

The Photography Tip of the Week #073

Posted by Philip in Photo Technique, Podcast

More than just focus

073 Photography Tip of the Week (audio)

What are the things that are most appealing about portraits? I have my short list, and an image to illustrate.

1) Off center lighting. The light shouldn’t be coming from the flash mounted on your camera or a flash on the camera.

2) Blurry background. This helps you to focus on the subject and not notice that squirrel in the tree.

3) Eyes that are sharply in focus.

In this image of Lauren, I have those 3 requirements covered quite nicely. The first two are easily achieved. If you have your flash off camera, you get number one. And as long as you know how to dial down your aperture, getting a blurred background is easy. But getting the eyes in sharp focus takes a bit more than just focusing on the eyes. You see one thing many people don’t realize is that there is more to focus than just focusing.

There are more factors involved in getting a sharp image out of the camera than just focus.

You need to have plenty of light on your subject to get the sensor to distinguish between the pixels. You need to have your pixel sensitivity or ISO turned down, 100 if you can but most cameras work quite well at 200. Your lens isn’t at it’s sharpest wide open. In this case I could have set it at f3.5, but the lens is actually sharper between f5.6 and f8. The smaller aperture means that the light goes through less surface of you lens and thus makes more of the image in focus. Since I wanted to blur out the background I chose the more open end of that, f5.6. And finally your shutter speed needs to match. This is a hard concept for many people. When you think of a shutter speed of 1/10 of a second you think you will have a blurry image and difficult to focus. But that’s not the case since we are using a flash to illuminate the subject. The flash will freeze the action, so you just need the shutter to match your other settings for the environment.

1:1 of the original image out of the camera

Don’t believe me? Lets take a look closeup. This is part of the unmodified image out of the camera. There’s nothing done to this image other than the standard color correction. As you can see, the eyes are sharp. They have that classy glassy look to them that comes from being in sharp focus and having the flash (with a big umbrella) supplying enough light for the sensor easily capture the color of each pixel through a small portion of your lens. That can almost be consider an equation, but we’ll call it a recipe for a sharp portrait.

Jul04 3

The Photography Tip of the Week #068

Posted by Philip in Photo Philosophy, Podcast

Sensor Check

068 Photography Tip of the Week (audio)

When you have a nice warm summer day and the sun is high in the sky, it’s a perfect time to check your sensor for dirt and dust. This isn’t like having to deal with airport security. You aren’t going to get raked over the coals if your sensor is dirty. But it is valuable information and will help you have the sharpest images possible. So here’s what you do. Get a white sheet of paper and take it outside and put it on the ground in direct sunlight. This will be the whitest this sheet of paper will ever get. White balance isn’t all that important, but aperture is so put your camera on aperture priority and set it to f/22. Set your ISO to 100 so you’ll have the least amount of noise and focus on the corner of the paper. With the focus locked, fill the frame with the bright sheet of paper and take the shot.

Use the corner of the page to lock your focus.

That’s a wonderful masterpiece you have there now. In some cases if you have really nasty spots you’ll see them immediately. But in most cases you’ll have to load the image in an image manipulation program and play with the levels. What we’re looking at here is a sensor I haven’t cleaned on one of my older camera bodies. You can see from the level histogram that it is displaying mostly white which is good. If it isn’t like this, you may have a serious problem with your sensor.

The white masterpiece, but does it have dust and spots?

When you change the levels by moving the black level toward the white, you may see spots and debris on the image. Some of this may be on the lens. You can use multiple lenses at the same settings to compare and determine if the spots are on the lens or on the sensor. If you only have one lens, clean the lens between shots and compare those images. Any difference will most likely be sensor dust.

Adjust levels to make spots pop.

Now let me show you what a clean lens and sensor looks like. The regular white shot is as you would expect. Mostly white and a true masterpiece if you like photographing polar bears in a blizzard.

Probably a clean sensor.

When you move the black point here, you will start picking up the inherit noise of the sensor and the grain of the paper. No spots and splotches here. If you do feel that you need to clean your sensor, do this test first to determine if you really need to. If you do, clean the sensor and do the test again to see the difference. I wouldn’t suggest using glass cleaner or anything other than a professional sensor cleaning fluid and brushes. Even though you are actually cleaning a piece of glass protecting the sensor, non-specific cleaning products can leave the sensor with more streaks, spots and dust than what it started with.