Focus demands Resolution and Contrast

What determines sharpness and blurring in an image? Bertram Hönlinger, optics expert at ZEISS, talks about the performance of modern camera lenses and the limits of what is technically feasible.

Mr. Hönlinger, in photography the topic of “sharpness” is touched upon time and again. What exactly does it mean?

Bertram Hönlinger: One of my colleagues once put it like this: “Focus is an out-of-focus term.” By that he meant that there is no clear-cut definition of focus in photography. We see the concept much more on the subjective level.

But you are an optics expert. So I am sure you have a very specific image in your mind of what focus means.

Focus is closely related to depth of field. As soon as I focus on a point within a shot, say the eyes of a model when I am taking a portrait, a focal plane is created that ideally runs parallel to the camera’s sensor. One point on this focal plane will appear as a single point on the sensor – or almost will. It is a different story with the details in my motive points which lie either in front of or behind this focal plane: the rays of light reflected by them do not meet at a point in the camera sensor, but are in fact spread across an area around the target point.

This is known as the circle of confusion …
— – —

continue at Zeiss

— – —

“The camera’s resolution capacity and the reproduction of micro contrasts makes all the difference when it comes to image definition.”

Advertisements

Wide-Angle Zooms

Play the angles and get the big picture with an ultra-wide zoom lens.
With zoom ranges starting at just 8mm for APS-C format lenses, and 11mm for full-frame, you can shoehorn vast areas into the image frame. They’re great for shooting sweeping landscapes or architecture, and arguably even more useful when shooting indoors, where space is limited – but that’s just the start of the fun.

A key attraction of ultra-wide lenses is that you can create images with extraordinary perspective effects. Get in close to the main subject in a scene and you can massively exaggerate its relative size, against a shrunken, receding background. Parallel lines appear to converge at alarming rates and shots generally have a proper wow factor. Another bonus is that short focal lengths equate to huge depths of feld. Unlike portraiture, where it’s often favourable to blur the background, wide-angle lenses enable you to keep very close subjects and the distant horizon simultaneously sharp.

Barrel distortion can also add to the creative effect, especially when using wide-angle zooms at or near their shortest focal length. That said, all of the lenses in this test group are ‘rectilinear’, aiming to keep distortions to a minimum. The alternative is a fsheye or ‘curvilinear’ lens, which give even greater viewing angles but with more barrel distortion.

— – —

Wide-Angle Zooms
Matthew Richards fnds the best buys to fit your Canon DLSR.

via Photo Plus – The Canon Magazine

Super-Telephoto Zooms: Canon vs Fujifilm vs Nikon vs Pentax vs Sigma vs Sony vs Tamron

Whether you’re shooting sports, wildlife or something else altogether, sometimes a standard telephoto zoom lens just can’t get you close enough to the action. A supertelephoto zoom lens will extend your reach signifcantly – and there are plenty to choose from.

A zoom range of around 100-400mm has long been a popular option to include in lens ranges (there are four included here), but some manufacturers have been pushing the envelope, super-sizing focal lengths to as much as 600mm.

Apart from the Fujiflm X-mount lens, all of the contenders in this group are fully compatible with both full-frame and cropsensor cameras. Naturally if you fit them to an APS-C format camera, you can extend your effective reach even further, with a 1.5x multiplication effect (1.6x for Canon cameras). Typical attractions include fast autofocus systems and optical image stabilisation, but there can be notable differences in features and performance. Let’s take a look at what’s on offer…

— – —

Matthew Richards tests the leading lenses for bumping up your telephoto reach
The Contenders
1. Canon EF 100-400mm f/4.5-5.6L IS II USM
2. Fujiflm 100-400mm f/4.5-5.6 R LM OIS WR
3. Nikon AF-S 200-500mm f/5.6E ED VR
4. Pentax 150-450mm f/4.5-5.6 ED DC AW HD
5. Sigma 100-400mm f/5-6.3 DG OS HSM | C
6. Sigma 150-600mm f/5-6.3 DG OS HSM | S
7. Sony FE 100-400mm f/4.5-5.6 OSS G Master
8. Tamron SP 150-600mm f/5-6.3 Di VC USD G2

via Digital Camera World

NIKKOR Lens Simulator

You can simulate images shot with various combinations of lenses, ranging from wide-angle to telephoto, and cameras, in different formats. Image varies with the value of the focal length.
Select any combination you are interested in.

— – —

NIKKOR Lens Simulator
try it at Nikon

Test our lenses | Fujifilm X Mount Lenses

Test our range of lenses and see how different lenses and aperture values affect the image.
1. Choose a lens
2. Choose aperture value (and zoom if available)
3. Click the “Take Photo” button
To view and compare your images, click the “View Lightbox” button.

— – —

Test our lenses | Fujifilm X Mount Lenses
try it at Fujifilm X Mount

— – —

Andy Marcus Shares His Lens Selection Process

As a New York City-based studio portrait and wedding photographer, Andy Marcus requires high performance and low distortion in his interchangeable lenses. His brand of choice is Sigma, he explains, “the focusing speed on [Sigma’s] lenses is exceptional. I’m also always impressed with their sharpness and images with no distortion.”

But the reason Marcus selects a specific Sigma lens depends on what it does best for the type of shot he needs to take. We asked Marcus to share which Sigma lens he used in four spectacular photos from his extensive portfolio, and why he felt it was the right lens for the shot.

Captured with the Sigma 24-105mm F4 DG OS HSM lens. Photo © Fred Marcus Studio

Captured with the Sigma 85mm F1.4 DG HSM Art lens. Photo © Fred Marcus Studio

Captured with the Sigma APO 70-200mm F2.8 EX DG OS HSM lens. Photo © Fred Marcus Studio

— – —

Andy Marcus Shares His Lens Selection Process
more details at Photo District News