What is equivalence and why should I care?
1 Depth-of-field equivalence
The concept of 'equivalence*1' is still somewhat controversial and not always clearly understood. We thought it was about time we explained - and demonstrated - what equivalence means and what it doesn't.
What is equivalence?
Equivalence, at its most simple, is a way of comparing different formats (sensor sizes) on a common basis. This is already the way most lenses are talked about: it's quite common to say that a compact camera includes a '28-120mm lens' but the key and (often unspoken) word in that description is 'equivalent.' It's a simple way of describing the range of fields-of-view that the lens offers, cancelling out the effect of sensor size by using a common reference point.
A 100mm equivalent lens on a small-sensor camera will give the same framing and (because that means shooting from the same position) the same perspective as an actual 100mm lens does on a full frame camera, regardless of sensor size, because they are equivalent.
|Crop factor||Focal length||Diagonal Angle
of View *2
|Canon EOS-1D X||Full Frame (864mm2)||43.3mm||1||100mm||24.4deg|
|Olympus OM-D E-M5||Four Thirds (224mm2)||21.6mm||2||50mm||24.4deg|
It's this logic that the idea of 'crop factors' is based on. The 'Four Thirds' sensor format has a diagonal very close to half that of a 'full frame' sized sensor. And, sure enough, if you calculate the angle-of-view of a 50mm lens on a system with a crop factor of 2, it's the same as for a full frame camera with a 100mm lens.
|Equivalence helps compare different lenses and cameras by using 35mm 'Full Frame' as a reference point. This doesn't mean that Full Frame is the best, or even the optimal format, it's just a reasonably well understood point of comparison.|
However, it's not just focal lengths that can be thought of in equivalent terms. In our recent reviews of fixed-lens cameras, we've tended to include a chart showing 'equivalent' aperture values and how they change as you progress through the zoom range. In the rest of this article, we'll discuss and demonstrate how apertures and sensor sizes interact.
The reason we do this is because it's become quite common, for any given part of the market, to have to choose between cameras with different lenses and sensor sizes. This wasn't such a common problem in the film era since 35mm was the de facto standard. As such, most people didn't need to directly compare quality and characteristics across those different formats. 35mm was better than 110, medium format was better again and large format was still better. In the digital era, the significance of (and difference between) sensor sizes isn't always appreciated, not helped by a rather opaque naming system.
Apertures and F-numbers
It turns out, the relationship between sensor size and aperture is very similar to that between focal length and sensor size. It's the physical size of the aperture that defines depth-of-field, not its F-number. Two lenses offering the same angle-of-view with 25mm diameter apertures will give the same depth-of-field of shot at the same shooting distance and when viewed at the same output size.
So, let's consider the effect of that 25mm aperture in the lenses we've been discussing. Both lenses give the same angle-of-view, so you're likely to shoot them with the same shooting distance - since that way you'll get the same framing in both photos.
Now think about what that means in terms of F-number (focal length/aperture diameter). The 25mm aperture in the 100mm lens would be considered to be f/4 (100mm/25mm), whereas the same-sized aperture in the Micro Four Thirds lens would be an f/2 (50mm/25mm). The table below shows the calculated depth-of-field for the two lenses, shot at the same working distance:
|Camera||Focal length||Aperture diameter||F-number||Depth of field *3||Equiv.
|Canon EOS-1D X||100mm||25mm||f/4||Near 16.1m
|Olympus OM-D E-M5||50mm||25mm||f/2||Near 16.1m
As you can see, although the lenses are quite different, the 50mm f/2 lens is giving the same framing and the same depth-of-field as a 100mm f/4 lens is on Full Frame. As such, you can say that a 50mm f/2 for Micro Four Thirds is equivalent to a 100mm f/4 Full Frame lens in terms of both field-of-view and depth-of-field.
We don't expect you to take our word for this. Conveniently, it's become fashionable for manufacturers to produce 85mm equivalent, F1.2 lenses, which makes it relatively easy to show the ways in which they are, and aren't equivalent. We'll demonstrate this on the third page of this article.
*1. Not to be confused with 'Equivalents' - an influential series of abstract photographs by Alfred Stieglitz, and an approach to photography that they inspired.
*2. Calculated using TawbaWare's Angular Field of View calculator
*3. Calculated using DOF Master, with the lenses specified, focused to a distance of 20m
Jun 27, 2017
Jun 22, 2017
Jun 15, 2017
Jun 15, 2017
|.....the ROYAL LOTUS 2017/08/25-NEW YORK..... by Chiwat|
from Wild flowers
|Coffee and Mango cake by clicker88|
from Another cup of coffee
The venerable Canon PowerShot G1 was announced seventeen years ago this week, marking the start of a line of enthusiast-focused compacts that's still alive and kicking.
Super macro photographer Can Tuncer captured these incredible close-ups of a single peacock feather using a special setup and three different microscope lenses.
After successfully crowdfunding the Biotar 75mm F1.5, Oprema Jena is at it again. This time they're bringing back the Biotar 58mm F2: the world's only lens with a 17-blade aperture.
Adobe's move to a subscription model is treating it very well indeed. The company has posted record revenue for the second quarter in a row, hauling in a mind-boggling $1.84 billion.
More details have emerged about the potential sale of Blackstone's 45% stake in iconic camera brand Leica.
Popular mobile editing app Snapseed just got a major update that includes a new interface and 11 new presets for both Android and iOS, as well as adding the Perspective tool to the iOS version.
It might sound like a strange idea, but taking macro photos of boiling water can actually result in some really cool photographs. A good photo experiment for a rainy day.
The database was created to "break with the narrow lens through which history… has been recorded" by equipping those who commission photography with "the resources to discover photographers of color available for assignments.
Lensbaby has released two new optics for their special "optic swap system." The Lensbaby Sweet 80 Optic gives you that trademark sweet spot of focus, while the Creative Bokeh optic gives you 9 different drop in aperture plate options to play with.
TechCrunch has already posted their review of the upcoming iPhone 8 (not yet the iPhone X), and they're calling it "a look into the augmented future of photography."
Affinity Photo is a $50 photo editing software with no subscriptions. That's it – pay for it once and you're done. And we think it's actually pretty darn good.
Instagram is currently testing a major change to the app's profile layout: replacing the 3-photo across grid with a 4-photo grid... and some users are NOT taking the news well.
A report by USSRPhoto is shedding some light on the return of the famed Zenit camera brand. It seems the full-frame mirrorless camera they're working on will be made in part by Leica using components from the Leica SL.
According to a reliable Korean report, Samsung is developing a smartphone sensor that's capable of super slow motion. Translation: Samsung's next batch of Galaxy smartphones may be able to shoot 1,000fps.
This simple photograph of a seahorse and Q-tip has taken the internet by storm. We spoke to photographer Justin Hofman about how it was captured, and what it means to him.
After a massive leak last week, Profoto has officially debuted the Profoto A1: the company's first on-camera flash system that they're calling "the world's smallest studio flash."
"When the first hyperfocal distance charts were designed, someone decided that an acceptably sharp background contained some blur — enough to notice in a medium-sized print [...] After that point, nearly every other hyperfocal chart followed suit."
The Canon EOS Rebel SL2 (also known as the EOS 200D) is the company's impressively compact entry-level DSLR. Packing a 24MP APS-C sensor, DIGIC 7 processor and Dual Pixel AF, it promises a lot of bang for the buck. And while not mind-blowing, it handles most tasks very well.
Correct these four common composition mistakes and your photos will be more balanced, tell a better story, and lead your viewer's eye where you want it to go.
The rugged, compact 360° action camera Kodak unveiled at Photokina in 2016, the Kodak PixPro Orbit 360, is finally available in the United States.
iOS 11 launches tomorrow, and it'll save all of your pictures in a new high efficiency image format called HEIC. Fortunately, there's now a converter that will let you turn those photos back into JPEGs.
Photo protection company ImageRights recently released a new service that lets non-subscribers take advantage of their streamlined copyright registration system that checks for errors and fills out all the required forms for you.
What's the difference between a $200 circular polarizing filter and a $100 circular polarizing filter? Roger Cicala at Lens Rentals put six different filters through a few tests to find out.
A flurry of leaks reveal that GoPro's upcoming Hero6 will shoot 4K at 60fps, 1080p at 240fps, will cost $500, and is scheduled for announcement/release on September 28th.
Before he became the iconic director whose name we've all heard, a teenage Stanley Kubrick struck up a business relationship with New York’s Look magazine. No surprise: he was an incredibly talented photographer.
WD's new G-Technology G-Drive mobile SSD R-Series is a portable solid state option for photographers who want the reliability of an SSD in a rugged water and dust-resistant package.
Fast, stabilized and affordable is an appealing combination when it comes to lenses. With its latest 24-70mm F2.8, Tamron aims to upgrade autofocus speed and stabilization. We've got a full gallery from this updated full-frame zoom.
Photographer Clay Cook tells the story of his most ambitious photographic dream and career goal coming true: photographing A-list actress Jennifer Lawrence.
In an interview with a Chinese website, Nikon Japan's Director of Development dropped a bombshell, saying that a Nikon mirrorless camera "must be full-frame."
Here's a side-by-side spec comparison of two flagship devices with particular attention to the things that really matter – at least to people who prioritize photography features.