Lens Quality

Lesson 29 from: Fundamentals of Photography

John Greengo

Lesson Info

29. Lens Quality

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Summary (Generated from Transcript)

The topic of the lesson is lens quality in photography.

Q&A:

What are some factors that impact image quality in lenses?

Some factors that impact image quality in lenses include resolution, flare control, diffraction, chromatic aberration, distortion, vignetting, and bokeh quality.
How does resolution in lenses affect image quality?

Lenses are becoming sharper due to higher resolution cameras. Older lenses may not perform as well on newer high megapixel cameras.
What is flare and how can it be minimized?

Flare occurs when light strikes the front of the lens, causing ghosting and light hitting different parts of the sensor. Using a lens hood can help minimize flare and some lenses are better corrected for flare than others.
What is chromatic aberration and how can it be corrected?

Chromatic aberration occurs when color ghosting appears when shooting a solid object with light behind it. It can be corrected in-camera by enabling chromatic aberration correction or in post-production using software like Adobe Lightroom.
What is distortion and how can it be fixed?

Distortion refers to the bending or warping of straight lines in an image. Programs like Adobe Lightroom have tools to fix distortion in post-production.
What is vignetting and when is it a problem?

Vignetting is the darkening of the corners in an image. It can be a problem with fast lenses, wide-angle lenses, and cheap lenses. However, some photographers may intentionally use vignetting for artistic purposes.
What is bokeh and how does it affect image quality?

Bokeh refers to the quality of the out-of-focus area in an image. Good bokeh has a smooth and creamy appearance, while bad bokeh may show the outline of the aperture and appear jittery.
What factors contribute to the construction quality of a lens?

Factors like lens mount (metal or plastic), focusing ring grip, and click stops on the aperture affect the construction quality of a lens.
What are the different categories of lenses in terms of optical quality?

The optical hierarchy of lenses includes professional prime lenses, standard prime lenses, professional zoom lenses, standard zoom lenses, and superzoom lenses. Superzoom lenses tend to have lower sharpness due to their versatility.
How does using a teleconverter affect lens performance?

Using a teleconverter can lower the sharpness of any lens by one step on the optical hierarchy. It is generally not recommended to use a teleconverter with a superzoom lens, but it can still yield decent results with high-quality lenses.

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Lens Quality

All right, a final little section here on lens quality. And so we talked about the angle of view, we talked about the aperture, but there's also a few things that impact the image quality that you're gonna get from any particular lens. So, first off, we wanna talk about some of these optical challenges in making lenses. And we wanna have lenses with the highest resolution possible, and there is no rating on this, as far as a number, when you buy your lens, but lenses tend to be getting sharper because we have higher resolution cameras now. And so there are some older lenses which are quite nice but on newer cameras, with higher megapixels, they don't stand up as well as they used to back in the days of film and lower resolution sensors, and so that's one of the things that we're getting just inherently in the newer lenses. Some lenses deal with flare better than other lenses, and so when light strikes the front of the lens, it causes ghosting and light hitting different parts of the se...

nsor, and so this is why you wanna use a lens hood, and why some lenses are better corrected for lens flare than others. I talked about diffraction, when we stop our aperture down. And so what happens is that, when we stop our aperture down, the light hitting those aperture blades gets diffracted, sent in slightly different directions, which causes just a little bit of blurriness. So stopping down to f22 and 32 is not recommended, unless you really need it, because it's gonna cause a loss of sharpness on any particular image. Chromatic aberration. Chromatic, color. Aberration, ghosting. Color ghosting will occur when you are shooting a solid object that has light behind it, and so as the light comes around the solid object, the light kinda gets a little misdirected, and it doesn't land in the right spot on the sensor, and you get this color ghosting. Now, this can be corrected sometimes in camera. You can turn on chromatic aberration correction, or you can do it in post-production in a program like Adobe Lightroom. Hit the checkbox and it knows what lens you have, how bad that problem is, and can automatically fix it. Or you can even go in and manually fix it, where it looks for edge lines of a certain color and corrects it and de-saturates it, basically. And so it's something that'll happen even with the best of lenses in bad conditions, you might say. Distortion is something we talked a little bit about before. Barrel distortion is more common on wide angle lenes and pin cushion distortion is a little bit more common on telephoto lenses. And all lenses should be perfectly corrected, but the reality is is that all lenses have a little bit of distortion, and to fix this, programs like Adobe Lightroom will have a little checkbox or they'll have a slider where you can fix this up later. In most images, you're not gonna notice this is a problem, but if you have buildings and straight lines, you might see that and you might wanna correct for that, if you have a lens that has a bit of an issue with these. Vignetting is something we talked about earlier. It's a darkening of the corners, and sometimes we like it and sometimes we don't like it. It depends what type of photograph it is, and what you want from the photograph. This is a problem of fast lenses, wide angle lenses, and cheap lenses. In the early days, some of you might remember, we had TVs that had rounded corners, and that's because the image was really dark and blurry in the corners, because the lenses weren't very good at getting sharp edges. So they just said, "Well, let's just make it like this." And there were some TVs that were round, because they had really bad lenses, I think, at the time, and they couldn't get anything sharp from the corners of them. The bokeh, the quality of the out of focus area, and you know your getting picky about lenses when you're worried about the bokeh of this. And I'm not even going to get into the how do you pronounce it thing. There's a whole thing on the internet about it. I call it bokeh, it's my class, that the way I like to call it. (instructor and students laughing) So, a good bokeh is gonna have a smooth and creamy out of focus area. The bad bokeh, you might be able to see an outline of the aperture, and it's a little bit more jittery and less smooth, and so this is something that some people will grade and qualify. There is no number on this, it's just more of a feeling, it looks more smooth than it does over here. On the right hand side, it's not very good. It kind of goes bright and dark very, very quickly there. And so some lenses are a little bit better than other lenses. Construction of the lens. This is really important to me. I like working with a lens that feels good in the hand, that's comfortable, that focuses smoothly, has nice click stops on the apertures, things like that. And so, metal lens mounts, because I tend to change lenses a lot. The less expensive lenses will use plastic lens mounts. I like a real focusing ring with a rubber grip on it, so that I have a good area to grab onto. Distance scales, and there's other factors in here we'll talk more about as we talk about lenses. But there are some pretty big differences between the lowest end and the highest end lenses. And so, it's not just optical quality, it's the entire quality of that entire product that you're gonna be looking at. And so, when it comes to the optical hierarchy, of what are the best lenses and what are the worst lenses, it generally falls into this category of professional prime lenses, and so a prime, like a 200mm lens, is gonna be a really high quality lens. Next up is gonna be a prime lens, just your standard 50 or 35mm lens. They're not necessarily quote unquote pro lenses, they're just prime lenses. They're gonna be very, very sharp. Next up are your professional zooms, your 24-70, 70-200, 2.8. Kind of next down on the list of sharpness are gonna be your standard zooms. Now, the difference between the 18-55 and the 200... Noticeable, but not huge. You could shoot a cover of next month's National Geographic or whatever magazine you wanna think of with any of these, would be my guess, if it's a good subject. But when you get into the pixel peeping, you will notice greater sharpness with those primes, and especially those high end primes. The lowest on the list are the superzooms, the ones that zoom a really large range, you know, the jack of all trades, master of none philosophy. If you design a lens to try to do everything, sharpness is going to suffer a little bit. And what I have found is that teleconverters will take any lens and lower it by one step on this list. And so, what you probably don't wanna do is put a teleconverter on an 18-200 superzoom lens. Kind of falls off the chart then. But, if you use it on a high quality lens, you'll be getting decent results still, but it's gonna lower it just a little bit from its original native abilities without using teleconverters. We'll talk more about teleconverters in the gadget section in this class.

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John Greengo

John Greengo is an award-winning photographer specializing in outdoor and travel photography. Shooting for over 3 decades, John has developed an unrivaled understanding of the industry, tools, techniques and art of photography. When he's not traveling for a new shoot,

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Lens Quality

Lens Quality

Lesson Info

29. Lens Quality

Summary (Generated from Transcript)

Lessons

Class Introduction

Photographic Characteristics

Camera Types

Viewing System

Lens System

Shutter System

Shutter Speed Basics

Shutter Speed Effects

Camera & Lens Stabilization

Quiz: Shutter Speeds

Camera Settings Overview

Drive Mode & Buffer

Camera Settings - Details

Sensor Size: Basics

Sensor Sizes: Compared

The Sensor - Pixels

Sensor Size - ISO

Focal Length

Angle of View

Practicing Angle of View

Quiz: Focal Length

Fisheye Lens

Tilt & Shift Lens

Subject Zone

Lens Speed

Aperture

Depth of Field (DOF)

Quiz: Apertures

Lens Quality

Light Meter Basics

Histogram

Quiz: Histogram

Dynamic Range

Exposure Modes

Sunny 16 Rule

Exposure Bracketing

Exposure Values

Quiz: Exposure

Focusing Basics

Auto Focus (AF)

Focus Points

Focus Tracking

Focusing Q&A

Manual Focus

Digital Focus Assistance

Shutter Speeds & Depth of Field (DOF)

Quiz: Depth of Field

DOF Preview & Focusing Screens

Lens Sharpness

Camera Movement

Advanced Techniques

Quiz: Hyperfocal Distance

Auto Focus Calibration

Focus Stacking

Quiz: Focus Problems

Camera Accessories

Lens Accessories

Lens Adaptors & Cleaning

Macro

Flash & Lighting

Tripods

Cases

Being a Photographer

Natural Light: Direct Sunlight

Natural Light: Indirect Sunlight

Natural Light: Mixed

Twilight: Sunrise & Sunset Light

Cloud & Color Pop: Sunrise & Sunset Light

Silhouette & Starburst: Sunrise & Sunset Light

Golden Hour: Sunrise & Sunset Light

Quiz: Lighting

Light Management

Flash Fundamentals