What is equivalence and why should I care?
Real-world depth-of-field demonstration
Conveniently, it's become fashionable for manufacturers to produce 85mm equivalent, F1.2 lenses, which makes it relatively easy to demonstrate the ways in which they are, and aren't equivalent.
|Format||Focal length||F-number||Crop factor||Equivalent Focal length||Equivalent aperture|
Here we've used the ratio of the sensor diagonals (more commonly referred to as the crop factor), to work out the equivalent aperture. If it helps you relate this back to the difference in sensor area, which is ultimately what equivalence is about, you can use the square root of the ratio of sensor areas (it's essentially the same number).
Here we have a set of portraits all shot at F1.2. As you can see, the amount of depth-of-field varies with sensor size (and the consequent change in aperture diameter of the associated F1.2 lens).
Technically, what you're observing is background blur, which depends on lens design as well as depth-of-field. Optical design can dictate how concentrated or diffuse each blur circle appears - something worth remembering when you read press releases suggesting that it's just about the number of aperture blades.
You'll not be surprised to find that the cameras (and their lenses) end up blurring the background based on their sensor size. The question is, do they do so in proportion to the sensor-size difference?
Below we've shot the same portrait, but this time at 'equivalent' apertures.
As the Nikon 1 has the smallest maximum equivalent aperture, we'll stop the other lenses down to match it. The fourth column in the table below shows the F-number required on each lens to offer an F3.2 equivalent amount of depth-of-field, while the fifth column shows the closest available F-number to that target. The final column expresses the difference, in EV.
|Format||Lens||Max equivalent aperture||Common equivalent apertures||F-numbers equivalent to F3.2||Closest available F-number||Difference from ideal|
|Full Frame||85mm F1.2||f/1.2||f/3.2||f/3.3||f/3.2||+0.1 EV|
|APS-C||56mm F1.2||f/1.8||f/3.2||f/2.1||f/2.0||+0.2 EV|
|Four Thirds||42.5mm F1.2||f/2.4||f/3.2||f/1.6||f/1.6||+0.1 EV*1|
|1"-type||32mm F1.2||f/3.2||f/3.2||f/1.2||f/1.2||0 EV|
As you can see, the real-world examples bear-out the expectations to a pretty good degree - when set to 'equivalent' apertures, the background blur is very similar. It also helps illustrate the distinction between background blur and depth-of-field - the background dots have all been spread to a similar degree, suggesting the same depth-of-field, but the appearance of them varies, depending on lens design.
In this instance, the lens on the 1"-type sensor is producing more concentrated blur circles - making them appear darker. This suggests the lens exhibits lower levels of longitudinal chromatic aberration than the others, such that different colors are being focused at the same depth. This would explain why the blur circles are less spread out and why they appear black, rather than the more diffuse, green-tinged rendering the other three lenses are offering.
• Depth-of-field and background blur are not the same thing
• Equivalent aperture will accurately predict depth-of-field (except at very close focus distances)
• There's more to bokeh (the quality of out-of-focus rendering) than the number or shape of aperture blades
*1 The calculated optimal aperture for Four Thirds is f/1.64, whereas, mathematically, the lens setting marked f/1.6 should be f/1.59.
Jun 27, 2017
Jun 22, 2017
Jun 15, 2017
Jun 15, 2017
|Global Reach by cjf2|
|Maligne Lake by Pete of Oz|
from - Mountain Lake - (Full Colours only + A Border)
Photographer Rick Wenner recently captured an odd event called the Race of the Gentlemen with a rather odd camera: The Phase One XF IQ3 Achromatic, the world's only 101MP black-and-white digital back.
Buying used is a good way to save some dough, and with the right precautions you can protect yourself from falling victim to a scam.
This two-part video series takes a deep dive into the world of dynamic symmetry and geometric composition, using iconic photographer Henri Cartier-Bresson's brilliant photographs as a guide.
Award-winning photographer Jeremy Cowart tells the moving story behind this drone photograph, captured in the aftermath of the devastating wildfire in Gatlinburg, TN in 2016.
Happy 2017 World Photo Day! We asked everyone on staff at DPReview to share one photo that they took within the last year that makes them jazzed on photography. Here's what we chose.
French President Emmanuel Macron has lodged a legal complaint against a paparazzo who snuck onto the president's private vacation property to take pictures.
Ever wonder what the difference is between compressed, uncompressed and lossless compressed Raw files? Photography Life's Nasim Mansurov breaks it down for you in this informative article.
The oldest known portrait of a US president was just discovered after over a century in storage. It's going up for auction in October, where it's expected to fetch between $150,000 and $250,000.
If you're using the popular Sigma 24-70mm F2.8 Art lens with Sigma's MC-11 converter, listen up: you'll want to update your lens and converter firmware ASAP.
If you've heard it once, you've probably heard it a thousand times: never check in your camera gear when flying. This shattered $11,000 lens is what can happen when you do.
Lensrentals just did its first Cine lens comparison, pitting five top-notch 35mm primes against each other: the Zeiss CP.2 35mm T2.1, Canon CN-E 35mm T1.5, Sigma 35mm T1.5 FF, Rokinon Xeen 35mm T1.5 and Schneider Xenon 35mm T2.1.
A team of Google researchers have found that slightly warping watermarks when embedding them into images can help prevent automatic removal.
You don't have to empty your savings account to take your photography to the next level. These cheap buys cost about $50 or less, and come with outsized benefits for your photography.
Joey L, Dani Diamond, Brandon Woelfel and Jessica Kobeissi go head-to-head in an episode of "4 photographers shoot the same model."
The latest flagship phone from Asus combines a 12MP 1/2.55" Sony IMX362 main sensor with a smaller Sony IMX351 chip for 2x zoom and a background-blurring portrait mode.
The company behind popular photo editor Picktorial 3 just released the X-Pack: a preset package that allows you to add Fuji's in-camera film simulation profiles to your RAF files in post.
Photoshop. GoPro. Every once in a while a product emerges that defines a category. And sometimes, it vanishes just as quickly as it arrived on the scene. This week's Throwback Thursday remembers the Flip, the pocket camcorder everyone had – until they didn't.
The Nokia 8's dual-cam combines the image data from a 13MP RGB sensor and a 13 monochrome chip for better detail, improved dynamic range and lower noise levels.
The company behind retail giant B&H Photo has agreed to pay out $3.2 million in monetary relief and back wages to settle a discrimination and harassment case from 2016.
After a popular Facebook teaser and some studio portrait samples, Godox has finally officially released the Godox A1 smartphone flash and flash trigger. Cheap, versatile and innovative, color us intrigued.
Canon’s EOS 5D Mk IV has won the European Imaging and Sound Association’s Professional DSLR of the Year award, making this the third year in a row that the brand has beaten Nikon to the top spot in the professional camera category.
A photograph and quote tweeted out by former president Barack Obama has officially become the most popular tweet of all time, receiving over 1.3 million retweets and 3.4 million likes.
Edward Weston was one of the most influential photographers of the 20th century, and in this episode of Advancing Your Photography we learn the extreme technique he used to capture one of his most famous still life photos.
Instagram just released a small update that will make a huge difference if you're active on the photo sharing app: threaded comment replies.
Venus Optics has announced the price and delivery date of the second lens to join its Zero-D line up: the 15mm F2 for Sony’s E mount. A lens they've dubbed, "the world's fastest 15mm rectilinear lens for full-frame."
Cinnac is a new social network for photographers that will help you separate your good photos from your great ones through a Tinder-like community-based rating system.
The Canon EF 35mm F2 IS USM is an understated jewel of a lens, and one that we've enjoyed on a variety of cameras since its release almost five years ago. Its relatively small size and image stabilization make it a versatile tool for a variety of photography - check out our sample gallery.
You don't need a fancy studio or tons of gear to capture the kind of classic product photography you see in magazines. In this video, Dustin Dolby shows you how to do it with just a couple of speedlights and some know-how.
The life-logging camera is trying to make a comeback. Say hello to FrontRow, a live-streaming enabled life-logging camera from Ubiquiti that hangs on a necklace like a pendant.
When a prospective client approaches you, don't just say "yes" right away. Here's a useful list of questions you should be asking before you decide to take the job and name your price.