photography education

Perspective (AGAIN!)

Here we go again!

First thing. Distortion and perspective are not the same. In lenses "distortion" is defined as an aberration where the corners of an image projected by the lens pull outward (pincushion) or the corners pull inwards (barrel). Distortion is independent of focal length. It is controlled in the design of the lens and is affected by the placement of lens elements and the placement of the aperture diaphragm inside the lens. It cannot be corrected by anything you do with your camera. It is built into the lens. Post-processing software often provides tools to help correct distortion. Most lenses are corrected as much as they can be for distortion. Rectilinear lenses attempt to keep straight lines straight across the image plane. Wide angle rectilinear lenses do have a characteristic of stretching objects at the edges of the frame. this comes from trying to fit a very wide almost unlimited view onto a fixed size image sensor (or film). This is usually most noticeable when the camera is in very close to the subject. The cure for this stretching is to use a fisheye lens! But that introduces a whole set of other issues for another discussion.

An interesting point about this "wide angle distortion" is that it only affects 3-dimensional subjects. Let's take an example of a tennis ball photographed with a wide angle rectilinear lens. If the tennis ball is in the middle of the frame it appears perfectly round. If it is move off to a corner of the frame you can see that it gets stretched out into an oblong shape. However, if you make a print of the centered ball and put the print in the corner of the frame in place of the actual tennis ball the ball in the print remains round. 

2-tennis-balls.jpg
3-tennis-balls.jpg

But enough of that, it is just a distraction from what I want to talk about. If you want more information about lens distortion I invite you to take a look at this article from Zeiss

On to Perspective!

I seem to be on a perpetual quest to help photographers understand the affect on perspective caused by camera to subject distance and how it is not related to focal length. Perspective here is defined as the relationship between objects in the scene. Objects closer to the camera appear larger than objects farther away. Objects closer to the camera also appear farther apart from each other than do the object farther away. It doesn't matter what focal length lens you use. All lenses show the same perspective from the same camera position.

So, you ask, what about telephoto compression? Isn't that caused by using a long lens? No! Go back to the previous paragraph. Looking at it from the other direction, it says that objects further away from the camera appear to be closer to each other than objects closer to the camera. Focal length doesn't affect that. Focal length affects magnification and the field of view (how much of the scene fits into the frame). You don't even need a camera to see how this works. Go someplace that has a series of similar items spaced out evenly in front of you. Maybe a long stretch of road with street lamps or something like that. Stand a foot or two from the first object and notice the distance to the second object. Pretty far apart. Now concentrate on the 8th and 9th objects. They look closer together and more similar in size. There is your compression. Of course, you took your camera with you anyway. So put the camera on a tripod and take a photo with a short lens and another photo with a longer lens.

Take those two photos into your favorite photo editor and crop the photo taken with the short lens to match the image taken with the long lens. You will see that for the area of the photo that is common to both focal lengths the perspective (and compression) are the same. When we want to show this compression we, of course, will pick a longer focal length lens as cropping optically maintains image quality as opposed to digital cropping or making an extreme enlargement from film. Changing the lens just changed the magnification, though, not the perspective.

Here is a set of images from a train station in Kyoto, Japan. All were made from the same camera position at various focal lengths rom 18mm to 400mm.  Notice that perspective in the area outlined in purple, which is common to all of the photos, remains the same.

People, too!

The same thing happens in our portrait work. From the same camera position your subject will look the same (except for size) if photographed with a 10mm lens or a 100mm lens. Take a look at the following image. It shows a studio scene made with a 10mm lens on a full frame (35mm) digital camera. The camera is fixed on a tripod at 58 inches from the mannequin. If you drag the slider from the right side to the left you will reveal an image taken with a 100mm lens and resized down to match the size from the 10mm lens. Notice that the perspective on the face is exactly the same from both lenses, despite the vast difference in focal length.

Here we see the same setup photographed with an 85mm lens next to the setup photographed with the 10mm lens. Again, the perspective is the same.

85mm lens, not cropped

85mm lens, not cropped

10mm lens, cropped 

10mm lens, cropped 

Here is a set of photos made with the following lenses: 100mm, 85mm, 50mm, 35mm, 24mm, 20mm, 16mm, 15mm fisheye, and 10mm. Despite the extreme barrel distortion bending everything but the center of the image, even the 15mm fisheye shows the same perspective on the face (see below).

100mm, 85mm, 50mm, 35mm, 24mm, 20mm, 15mm, and 10mm from the same camera position 58 inches from the subject

Here are the 85mm and the 15mm fisheye cropped to the same framing...

85mm full frame

85mm full frame

15mm fisheye cropped

15mm fisheye cropped

For another take on this, please visit my previous post about the Incredible Shrinking Space Needle that is an excerpted from my book, Anatomy of a Studio Portrait, which is available on Amazon

And a quiz of sorts... 

This is also from Anatomy of a Studio Portrait.Can you tell what focal length lens was used for each of the above images?

From left to right, top to bottom: 200mm, 135mm, 105mm, 100mm, 70mm, 57mm, 38mm, and 24mm.

 

 

To round things out, all of the photos in this set were made with the same 24mm lens, but the camera to subject distance was changed attempting to maintain the same size head in each image. Distances are 20 inches, 24 inchces, 28 inches, 39 inches, 51 inches, and 60 inches.


What about full frame vs crop frame?

Easy enough. Same setup with two cameras. Full frame (Canon 5Diii) with a 50mm lens and a 1.6 APS-C (crop) frame (Canon EOS M5) with a 35mm lens. Camera to subject distance is the same (36 inches) in both photos. The facial features are the same.

50mm lens on full frame camera

50mm lens on full frame camera

35mm lens on APS-C "crop frame" camera

35mm lens on APS-C "crop frame" camera

Let's take it further and compare the 50mm lens on full frame with a 10mm lens on crop frame...

50mm on full frame again

50mm on full frame again

10mm on APS-C cropped to match

10mm on APS-C cropped to match


I hope this helps explain how distance affects perspective. Yes, you can get very widely different perspectives by using different focal lengths, but that is when and because you move the camera. Telephoto (long) lenses tend to make us back up away from our subjects making the scene look more compressed. Wide angle (short) lenses invite us to move in closer to our subjects making the scene feel more wide open. It is our moving in and out, though, that changes the perspective. The focal length of the lens then determines how much of the scene will be captured.

For even more on this topic, please visit the Understanding Camera Lenses article at Cambridge In Colour. And take a look at the other tutorials there. Sean McHugh does a great job at explaining photographic concepts with text, illustrations, and calculators.

Cheers!
John

 

Feathering your light

For my fine feathered friends!

feather.jpg

Back again to help clarify studio lighting terms. This time I am taking on the concept of feathering. Feathering is pointing the light ahead of your subject instead of straight on to your subject. Feathering usually produces a nicer looking image. People often say a "softer" light on the image, but that isn't quite correct. Remember that the quality or character of light is determined by the size of the light in relation to the subject. You see this in the shadow edge transition. The larger the light source is the smoother the diffuse highlight to shadow transition is and the softer the light is.

Let's take a look at what happens when you feather the light. Here are photos of a 2x2-foot softbox straight on and the same softbox feathered off to one side. What do you notice first? I hope you see that the feathered light is SMALLER than the direct light. So, if the light remains the same distance from the subject, it is potentially slightly harder when feathered. But at the same time, it spreads out more across the face of your subject, giving a more pleasing look. 

Straight on the softbox is larger than when feathered

Straight on the softbox is larger than when feathered

Hard Light

Working with a softer (larger) light source it isn't so easy to see what is happening. Let's start with a harder light. This time a 7-inch standard metal dish reflector. 

7-inch reflector straight on and feathered 

Take a look at the 3 points labeled in the photo. A (the nose), B (the lower lip), and C (the ear).  A is the same brightness direct and feathered. Why? Because it is a specular reflection and is the same brightness as the light source, no matter the distance. If the light was moved in closer the brightness would stay the same but the reflection would get bigger. If the light source was moved back the brightness would again be the same, but the reflection would get smaller. The feathering doesn't have much of an effect here.

B is somewhat similar with the small hard light source. Basically the same straight on or feathered. At point C we can see that pointing the light more in front of and across the subject a little bit of light catches the ear. I would probably retouch out that little highlight on the ear. 

Go back to point A and the nose. This time look on the shadow side of the nose. The edge of the main dark shadow is about the same. With the feathered light the shadow is not as dense, but the edge transition line is pretty much the same. The feathering lowered the contrast, but didn't make a softer transition. It didn't soften the light.

Soft Light

Now let's work with a softer light. This time a 2x2-foot softbox. 

24x24-inch softbox straight on and feathered

The differences are more subtle, but they are there. Look at the same three points as before. The brightness of the specular highlight on the tip of the nose is the same brightness straight on and feathered. But this time there is a difference in point B on the lower lip. Feathering the light changed the shape of the wide highlight on the lip, but the brightness is still the same. The larger light also allowed more  light to reach the ear than with the 7-inch dish above. 

Again, I invite you to look at the shadow side of the nose. There is very little difference in the shadow edge transition. Feathering did not make it softer.

Comparison sliders drag to the left to see the feathered light, drag to the right to see the direct light

Hard vs Soft

Below are the feathered light images with the small and the larger light sources

Comparing the 7-inch and the 24-inch light sources

Look at the same points again. A is pretty close in brightness, but the shadow edge on the shadow side of the nose is very different. That comes from the difference in the size of the light sources, not from the feathering. The larger light makes for a nicer looking highlight on the lower lip (B). If I had move the softbox back further away from the face it would have been smaller and brighter. Brighter because the rest of the face would have received less light and I would have to have compensated by turning up the power of the light (strobe) or used a longer shutter speed (constant light, which is what I used for these demonstrations). As noted above the specular highlight remains the same brightness, but I would have had to brighten up the entire image, including the specular highlight to maintain proper exposure on the face. I know that  this can be confusing. So let's look at another illustration.

Controlling the size and brightness of specular highlights

Again I am using a constant light, so I am controlling my exposure via my shutter speed. If I was using flash here I would vary the power of the flash to maintain the same exposure on the subject of the photo. With the light 40-inches from the can the highlight is thin and bright--too bright to read the text on the label. As the light is brought in closer a couple of things happen. 1. The highlight gets wider because the light is closer and therefore larger in relation to the subject. 2. I have to lower the overall exposure so the diffuse reflection of the can is properly exposed. This brings down both the overall exposure and the specular highlight brightness, bringing them closer in line with each other. In the third image the light is very close and its reflection is even less noticeable because it is spread out over a larger area and the brightness of the rest of the can has been brought up closer to the brightness of the highlight (and then the overall exposure was lowered to bring it all back to give the proper exposure of the overall subject). I know this can sound counter-intutive. Bringing the light in closer reduces the mirror-like specular reflections.

We see the Inverse Square Law doing its thing here. As the light is moved closer to the subject it falls off faster and the background gets darker. As the light is moved in closer the specular highlight remains the same brightness, but gets larger. As the light is moved in closer the overall diffuse reflection exposure gets brighter and we have to lower the intensity of the light.

BOTTOM LINE

Feathering your light can change the size and shape of specular highlights, but the brightness will stay the same. Feathering your light will help even out the exposure across your subject, but won't have much effect on the shadow edge transition (softness). Feathering your light is the right thing to do. If you want to tone down a hotspot you need to move your lights in closer. But that also affects the depth and spread of the light. So many tradeoffs in photography. More details about the tradeoffs are in my book, Anatomy of a Studio Portrait.

Thanks again for stopping by!
John Cornicello

 

Lighting Workshop Results

Lots of learning going on

Last weekend I presented a program on speed light and flash control at the Olympic Peaks Camera Club. I followed up on that with a 3-hour hands-on workshop on studio lighting on Saturday. I will be presenting a similar workshop at Glazer’s Camera in Seattle in November.
During the second hour of the class the students got to photograph each other using the Interfit S1 battery powered studio lights. I set up two lighting stations for them. One had an S1 head in a 2x3 softbox and the other had an S1 in a 46” Phototek Softlighter II. Each also had a white reflector set up opposite the key light and a background with no light on it.

Photo by James Hagen

One of the students, Jim Hagen, shared a portrait he made of another student, Irv Mortensen. This portrait was made with the S1 in the 2x3 softbox. I asked Jim about his experience in photography in general and more specifically about portraits. His response was, “(I) bought my first DSLR a little under two years ago. Didn't know aperture from my arse. Shot a lot of photos previous but with point and shoot auto. These are the first portraits I've taken. Very excited about how things were set up and the possibities of learning lighting and flash techniques. Certainly off to a running start after Thursday and Saturday!

Photo by Irving Mortensen

Irv then made a portrait of Witta Priester using the same setup. Witta then turned around and made a portrait of me on the other set with the Softlighter and lighter color backdrop.

One of my little "tricks" with the 2x3 softbox is to put strips of thin black masking tape across the front of the diffuser to make it look like window panes in the catch lights on the eyes of my subjects. 

Great job by Jim, Irv, and Witta. I know that many photographers are not comfortable on the other side of the camera. But I feel that if you are going to make portraits you should get used to being in front of the camera. If you don’t have someone around to photograph you, a project of self-portraits can be great experience. 

The Interfit S1 lights are very simple to operate with clearly marked controls and no hidden "secret handshake" button combinations to memorize when adjusting the lights. See the photo of the unit below. 

 

 

Feathering the light and adding a reflector

Photo by Witta Preister

Clean and easy to use control interface

Thank you to Val for inviting me to present. Thanks to Rebecca and John for their great hospitality feeding me and giving me a home base for the weekend. And thanks to everyone who came out for both the meeting and the workshop. I had a great time and look forward to another trip to Sequim, WA with all of its lavender glory.