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A Brief Review of the Sigma 24mm f/3.5 DG DN Contemporary for Sony E

My favorite “walking around” and landscape focal length is 35mm equivalent. I have some 24mm lenses which approximate that field of view on my APS-C camera. One is the Tamron 24mm f/2.8. But despite its great resolution, it is slow to focus and pretty large. So after being very pleased with my Sigma 45mm Contemporary, I decided to give their new 24mm version a try. I’m glad I did.

Although I plan to use it mostly on my APS-C camera, all test shots were made on my full-frame Sony a7R IV in order to explore the edges of the full-frame field.

Many photographers favor a real aperture ring like this Sigma. But note that I’ve set mine at “A”. That gives control of aperture to the camera. I prefer that because I often shoot the same scene at several apertures and this allows me to select apertures without moving my eye from the viewfinder.

Macro Capable

Both Sigma and Tamron 24mms have semi-macro capability of 1:0.5. And both are sharp. Shooting at closest focus puts the lens on top of the subject, blocking light. But it worked well for these two examples, which were shot about a foot away from the subject.

Remember that the depth of field of any shot increases with distance squared. So shooting from twice the distance quadruples the DOF. That is very nice to have with close-up shots.

Bird of Paradise
Liquid Amber Burr

Sharpness

I explained my sharpness testing method in this article. I shoot a sloped roof, then find the largest aperture that gives sharp sides, as shot or with a touch of sharpening. This lens achieved that wide open, which is rare.

Shot at f/4. The left inset is cropped from the left side and the center inset from the center. Click to enlarge.

I’m content with any lens which will do that at least at f/11 because I usually shoot at f/11 or f/16 for depth of field. And on the occasions when I use large apertures, I want soft sides.

Chromatic Aberration

I can’t see any, on- or off-center.

Flat Field

This wide-open test shot demonstrates the flat field. The shot is made by photographing pavement at an oblique angle, then processing the image with an editor function that replaces sharply focused edges with white marks. The pattern of white marks is essentially straight from left to right, indicating a flat field.

Flat field

Field curvature doesn’t bother me because I usually want depth of focus and use small apertures where field curvature disappears. And if I’m using larger apertures, that is to isolate the center of the shot and I want blur off-center.

Focus

Autofocus is quick and accurate like most quality lenses. Manual focus is about average for autofocus lenses, which is slower than I like.

Vignetting

Vignetting at large apertures is a fact of life with wide-angle lenses. When I made these test shots I was puzzled at how little vignetting I could see. How did Sigma do that? They seem to defy the laws of physics.

Photos shot at f/4 (left), f/5.6 (center), and f/8 (right). Click to enlarge.

Conclusion

I’m very happy with this lens. And it’s a nice bonus that it also has closeup capability.

Some might seek a larger aperture, but I have little use for very large apertures in wide-angle photography. And I don’t like the great weight of f/1.4 wide-angle monsters.

Sample Photos

Although I usually sharpen my photos, none of these samples has been sharpened. In shooting lens review samples, I aim for detail over all of the image for most samples, rather than artistic merit.

f/4
f/4
f/5.6
f/8
f/8
f/16


About the author: Alan Adler lives in Los Altos, California. The opinions expressed in this article are solely those of the author. He has been an avid photographer for 60 years. He is also a well-known inventor with about 40 patents. His best-known inventions are the Aerobie flying ring and the AeroPress coffee maker.

An Intro to the Most Basic Photo Edits for Folks Who Don’t Edit (At All)

This article is aimed at folks who don’t edit their photos at all. If you aren’t editing you’re missing a lot of fun. Think of me more as a cheerleader than a teacher. I’ll show you simple edits that can be done in a few minutes. We won’t be adding non-existent clouds nor making fat people thin. This is just simple stuff. Let’s start with this shot.

My first step would normally be to level the horizon, or rotate until the trees or buildings were vertical. But this image didn’t need that. So well proceed to the second step, called “dehaze” which removes haze that you didn’t know was there until you removed it.

Before (left) and after (right) dehaze.

Now, before doing any more edits, save this as “filename-dehaze”. By saving your image with “save as” every step of the way, you can easily go back and try different things. Do you wonder what a given edit will do? Don’t wonder. Try it. You don’t have to keep it.

Next we’ll adjust exposure. You can play with brightness and contrast or use “curves”. This example used “curves” which allows you to adjust contrast or brightness in the highlights or the shadows, or both.

Next I cropped the image, eliminating the leaning tree on the right. Because I save every step, I can always return if I don’t like the way it’s going.

Next we’ll adjust color saturation.

Increasing saturation strengthens colors. But occasionally you might want to reduce saturation, for a pastel effect.

Now we’re almost done and we’ll sharpen the pic. It’s already sharp, but I call moderate sharpening a free pass to greater image quality. Watch out for over-sharpening, which adds “artifacts”, especially at high contrast edges. If you don’t exceed a radius of 2 pixels, you’re pretty safe.

Finally, I resize the image to 1500 pixels wide, for publication or sharing by email.
Because I saved every step I can always go back and play again.

And here’s the image converted to black and white.

I deliberately didn’t provide a lot of details for each step because I want you to learn by experimenting, rather than from what I tell you.

I do edits like this often, sometimes in just a few minutes. It’s great fun.


About the author: Alan Adler lives in Los Altos, California. He has been an avid photographer for 60 years. He is also a well-known inventor with about 40 patents. His best-known inventions are the Aerobie flying ring and the AeroPress coffee maker.

Fixed Prime Lens Photography — Zoom by Cropping

I haven’t lusted for a fixed prime camera because it’s so easy for me to mount a short prime lens on my ILC. But I am intrigued by the idea of walking around with a short prime on my camera, even though it is limiting compared to walking around with a zoom.

We can zoom our prime shots by cropping.

Most full-screen images published online are 1200 to 1500 pixels wide. My Sony a6400 sensor is 6000 pixels wide, so there’s room to crop or resize. When I crop out a fourth of my original frame, the field of view approximates a 4x longer lens. Thus my 32mm shot crop below has the field of view of about a 135mm lens.

The examples below were shot with my 18-135mm zoom to create images with various focal lengths lenses.

This is the original 135mm focal length image downsized from 6000 to 1500 pixels for sharing or publication online:

This is a 32mm focal length image shot from the same place, cropped to 1500 pixels wide :

Here are 500 pixel crops taken out of above two images to aid pixel peeping:

Crops from 135mm image (left) and from 32mm image (right).

Theoretically, the 135mm image should be better because when it was resized from 6000 pixels wide down to 1500 pixels, extra information was packed into the resized image. But it’s very difficult to detect that, even with the help of these crops.

None of the above images were sharpened. But I normally sharpen because, when done in moderation, it’s a free pass to improved image quality.

You can push the 4:1 ratio farther if you’re willing to accept the image degradation caused by upsizing your cropped image. I tried upsizing a pic of this scene shot with my lens at 18mm. It required upsizing 1.88x and looked pretty rough. Next I tried simulating a pic of the scene as if shot at 26mm which required 1.25x upsizing. Here is a crop of it compared to the others:

From 135mm image (left), from 32mm image (center), and from 26mm image (right).

And above is the full image. This required 1.25x upsizing and 50% sharpening. The ratio between this shot and the original 135mm shot is about 5.3x.

My take on this experiment is that, if my shared or published images are 1500 pixels wide, cropping out a fourth of my 6000-pixel frame produces image quality that’s very close to a resized image shot with a lens of 4x longer focal length. And with slight degradation I can push the ratio 5.3x. 4x is like a 35mm lens that can be cropped to range from 35mm to 140mm. 5.3x would be like 35mm to 185mm.

This same criteria applied to a 61-megapixel Sony a7R IV with its 9565 pixel sensor width would permit a ratio of 6.38x which is like 35 to 223mm or 35 to 279mm with 1.25x upsizing.

Now let’s consider how this applies to some fixed prime cameras:

The Leica Q sensor is also 6000 pixels wide and the lens is 28mm. The same criteria would allow a range of 28mm to 112mm or 28mm to 140mm with 1.25x upsizing.

The Leica Q2 sensor is 8368 pixels wide and the lens is 28mm. The same criteria would allow a range of 28mm to 156mm or 28mm to 195mm with 1.25x upsizing.

The Fuji X100V sensor is 6240 pixels wide and the lens is 23mm. The same criteria would allow a range of 23mm to 96mm or 23mm to 120mm with 1.25x upsizing.

You can do your own experiments by shooting the same subject, from the same spot, with focal lengths that differ by 4x, 5x, or whatever ratio you want to try.


About the author: Alan Adler lives in Los Altos, California. He has been an avid photographer for 60 years. He is also a well-known inventor with about 40 patents. His best-known inventions are the Aerobie flying ring and the AeroPress coffee maker.

In Praise of Inexpensive Lenses

When I was a semi-professional 4×5 landscape photographer I often spent a half-hour shooting a single sheet of film and several hours enlarging it to the best of my ability. I sought the sharpest possible result. And now in the digital age, I still pursue sharp images.

Phillip Reeve writes on his website that he has two hobbies, photography and photographic equipment and they rarely intersect. I too enjoy both creating photos and testing lenses. The two hobbies are different.

My second hobby has led me to discover that lightweight inexpensive lenses perform well at the smaller apertures that I usually choose for depth of field.

I enjoy taking my Sony a6400 along on daily walks and often take the smallest zoom lens available, the 16-50mm. It weighs only 117 grams and is very flat. Photo writers often recommend that you ditch this cheap “kit lens” and replace it with a “real lens”. But in my tests, it matched my best 35mm Zeiss prime at f/5.6 and smaller apertures.

Sony a6400 with 16-50 kit zoom extended.

Zooms and Primes

When zoom lenses first became common, I thought they weren’t good enough and only used primes. But with time zooms improved and I learned that they often match or even exceed the sharpness of primes, especially at small apertures and with a bit of sharpening in edit.

At large apertures, cheap lenses are reasonably sharp on center. It’s off-center where they may be soft. But when I do use large apertures, I want blur off-center to highlight the central “star” of the shot. Of course, composition goals might dictate placing the “star” off-center, but I shoot it on center, where lenses are best, and crop for composition.

Isolated “star” subject
Another isolated subject

Quantitative Testing

I love imatest test results. When first investigating a lens, I Google “lens-name, imatest”. I find that a good starting point. But if lens “A” has imatest result of 2,000 lines and lens “B” tested at 3,000 lines, how do I relate that to my photos? To answer that I seek test pics. Cameralabs and Phillip Reeve offer test pics on and off-center at all apertures. Also, I often shoot my own tests.

Shot with the Sony E PZ 16-50mm f/3.5-5.6 OSS at f/11.

My favorite test subject is a sloped shingled roof. As Lensrentals founder Roger Cicala teaches, an oblique shot shows sharpness and field curvature. He also teaches that field curvature is rarely a problem. More about that later. Roger likes to shoot grass and that works, I’ve come to like shingled roofs.

All roof shots except “composition shingles” were made with Sony a6400 and 16-50mm kit zoom.

The test roof
Composition shingles

Sharp lenses capture the grainy quality of the crushed rock on composition shingles. Wood shingles are good too. Another advantage of an oblique subject is that if you miss perfect focus, it’s probably there, a bit higher or lower in your frame.

Recently I shot this roof with several 35mm primes and zooms at all their apertures. I examined the sides of the image to determine at what apertures the sides reach their best sharpness. This was f/5.6 to f/8 for most good lenses and every lens I tested had sharp sides at f/11. My cheap 16-50 “kit lens” surprised me by achieving sharp sides at f/5.6 and smaller when slightly sharpened. That’s excellent.

Crops of test roof. Color shift is present in the entire roof image above

Center crop (left), right side (center), and right side sharpened (right).

My Zeiss ZA 35mm f/2.8 had sharp sides wide open. When I saw this, I was amazed and delighted. But then I realized that even though this lens has sharp sides wide open, I would usually stop down to f/11 or f/16 for depth of field. And on the occasions when I did use large apertures, I would want soft sides. So the outstanding performance of this lens was of little advantage over lesser lenses.

Shot with the Sony E PZ 16-50mm f/3.5-5.6 OSS at f/11.
Shot with the Sony E PZ 16-50mm f/3.5-5.6 OSS at f/11.
Shot with the Sony E PZ 16-50mm f/3.5-5.6 OSS at f/11.

Why I Don’t Fret About Field Curvature

I usually want depth of focus and use small apertures where field curvature disappears. And if I’m using larger apertures, that is to isolate the central “star” of the shot and I want blur off-center.

Shot with the Sony E PZ 16-50mm f/3.5-5.6 OSS at f/11.
Shot with the Sony E PZ 16-50mm f/3.5-5.6 OSS at f/11.
Shot with the Sony E PZ 16-50mm f/3.5-5.6 OSS at f/11.

A “Good Lens”

The widely accepted definition of a good lens is one that’s sharp over the entire frame at a wide aperture. The ZA 35 mentioned above would be considered “very good” because it achieves that wide open. But I’m happy as long as my lens is sharp over the entire frame at least by f/11. To date, every lens I’ve tested meets that. And because I like light weight, I often walk around with my cheap lenses, which are my lightest.


About the author: Alan Adler lives in Los Altos, California. He has been an avid photographer for 60 years. He is also a well-known inventor with about 40 patents. His best-known inventions are the Aerobie flying ring and the AeroPress coffee maker.