Sony a7s

The Sony A7s is being heralded as “Camera of the Year” by some reviewers, Frederick and I take a look at the third camera in Sony’s a7 series. While offering a sensor with only 12MP, the a7s is getting a lot of attention for a sensor that can shoot up to ISO 409,600 as well as being one of the first still-image camera that also produces 4K video.

Does it live up to all the buzz? And who really needs a camera that can shoot in the dark? And what about that 12MP sensor? Isn’t that really heading in the wrong direction? I explains why 12MP may be enough for you and why a high-ISO sensor may be important to everyday photography.

Sony a6000

The a6000 replaces Sony’s NEX-6 and at only $600 (body only, street price) you might think this is just another entry-level camera, comparable to a point-and-shoot. But you’d be wrong. Sony claims this is the world’s fastest autofocusing mirrorless camera and is now the top-of-the-line in their APS-C sensor line.

I put the a6000 through some serious usage tests including an intense week of shooting on the streets of New York City. And while Frederick and I lament the fact that Sony still doesn’t appear to understand the value of features like touch screens and external mic jacks, you’ll also hear whether I think the a6000 is a good choice regardless of these weaknesses.

Canon 70D

MDe9150b77-2804-435d-aae4-9e3f164c7aa0 Although much of the buzz this year has been about small, mirrorless cameras, the big-boy DSLR makers (Nikon and Canon) haven’t been entirely asleep at the switch. The new Canon 70D is most notable for it’s groundbreaking Dual Pixel CMOS autofocus sensor, which is used in video and Live View modes. The Canon 70D and an explanation of autofocus technologies are the topics of this episode of All About the Gear.

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How Does Sensor Size Affect Depth-of-Field?

Earlier today, Frederick Van Johnson and I recorded a pilot for a new series from This Week in Photo. The series is tentatively called All About the Gear and the pilot episode is The Olympus OM-D vs Sony NEX 7 – Is Mirrorless More, or Less?

In the show I made the statement (at about the 8:00 mark) to the effect that the depth-of-field on a micro four-thirds (MFT) camera at a given aperture (say f/4) would be the equivalent of f/8 on a crop-sensor camera like the Sony NEX-7. What I should have said was that it would have been the equivalent of f/8 on a full-frame (FF) body. That’s what happens when you try to talk faster than your brain can operate.

In any case, in the YouTube comments, Jamie MacDonald challenged that statement, saying “f/1.8 is f/1.8 It is ‘sensor agnostic’ if you will.” Jamie is technically correct and I was taking a shortcut for the benefit of simplicity, for which I apologize. However this continues to be a much misunderstood issue, which I think deserves a more complete explanation.

Imagine you’re taking a picture of a tree with two cameras, both equipped with zoom lenses, from the same location. One is an MFT and the other is FF. Let’s assume both are set to an aperture of f/4. You compose your shot on the MFT camera and it turns out to  require a focal length of 45mm. Now you compose the exact same shot on the FF camera. The tree is the same size (in terms of percentage of frame height) in both viewfinders. If you check the focal length on the FF camera, you’ll see it’s set to about 90mm. Same shot. Same aperture. Different focal lengths.

Now go home and look at both images. You’ll see that the image from the MFT camera has a much greater depth-of-field, while the one from the FF has much more boken, or blurring as you get away from the in-focus area of the image. Why, because of the difference in real focal length as opposed to equivalent focal length. (We say that 45mm on the MFT camera is the full-frame equivalent of 90mm because of the size of object in the frame from the same distance.)

As Jamie correctly points out, this is not actually due to the aperture, since it’s the same in both cases. But here’s the thing: If instead of shooting the FF image at f/4, you use f/8, now you would find the depth-of-field in the resulting images was nearly identical.

The superzoom on my big Nikons is 28-300mm. An equivalent superzoom on an MFT camera is 14-150mm. Those lens/camera combinations give me the same image-area range. I most-often shoot in aperture-priority mode, so with my FF camera I might decide to use f/11 to give me the desired depth-of-field for a particular shot. In order to get the same depth-of-field using the MFT camera, I need to set it to f/5.6.

So what does this mean in practice? When using lenses of equivalent focal lengths such as the kit zooms on each, to get the same depth-of-field as a full-frame camera, you need to use an aperture about two stops wider on an MFT camera and about one stop wider on an APS-C crop-sensor camera.

Hope that helps.

And please: give us feedback on the new show. Here, on the TWiP blog or on the YouTube channel.