Technical Camera : Wide Converter Support

There are occasions when the iPhone camera is not wide enough. A handful of companies (Moment, olloclip, Schneider, Zeiss – just to name  a few) realized that this is an issue, and started making converter lenses that let you shoot wider. These lenses fall into two categories: 1) well corrected for distortion – like the Moment or Zeiss, and 2) uncorrected.

With the latter group you have severe barrel distortion. We started experimenting with these lenses for use with the Mark II Artist’s Viewfinder back in 2013. The barrel distortion basically made them unusable for simulation purposes, so we came up with a solution that’s unmatched even five years later. Maybe because it needs a lot of effort and is quite costly to implement.

The technology behind the solution is real-time distortion correction, and the associated thing in both Artist’s Viewfinder and Technical Camera is Wide Mode.

Let me show it in action before going deeper (veteran Artist’s Viewfinder users can skip this, as it’s exactly the same thing you’re used to in that app).

The top/left half of the image is what you get when attaching an uncorrected converter lens. The lower/right half is what you’ll end up after turning on Wide Mode.

This kind of correction is really important if you want to take architecture or real estate pictures – it may separate an amateurish looking image from a professional looking one.

Since distortion correction is done in software, edges of the resulting image may become soft. This is more pronounced with wider (0.5x-class) converter lenses. One possible mitigation (depending on planned image use) is using JPG Half or JPG Quarter image size for your album.

To use a converter lens with Technical Camera, you need to tell the app which lens you are using with the Wide Converter item in the menu. This will select the appropriate correction profile and conversion factor. We make dedicated profiles for each supported converter/phone combination (this is why it’s a costly endeavor). The list of profiles is continuously expanding, so if you miss something, please let us know.

We also measure the exact conversion factor for the profiles (which is usually more conservative that manufacturers tend to advertise). In Technical Camera this number is used for displaying Framing Previsor corners correctly.

But since we can’t cover every single lens on the market, there’s another neat thing: you can create a “custom converter” yourself. Since the process is exactly same for both apps, I’m not going to replicate here what I wrote about this feature when it was introduced in Artist’s Viewfinder – but I recommend you to read that post.

Ok, you have a converter selected. The lens is already attached to the phone. What’s next?

You have to activate Wide Mode. This is done with either the WIDE icon among camera options (accessed by tapping the circle icon in the corner – shown below).

Wide Mode icon on Camera Options

Or by assigning the Toggle Wide Mode (W) function to a Smart Function Key and operating that key.

That’s it. Until you turn Wide Mode off, the viewfinder, saved JPG images, and even preview images saved in RAW files will be distortion corrected.

All functions (exposure, focus, etc) operate the same way in Wide Mode, with the exception of digital zooming, which is disabled.

Technical Camera is available for pre-oreder now on the App Store, at a 30% discounted price. It will be released tomorrow.

Mark II Artist’s Viewfinder 5.0 Available

Version 5.0 of my Mark II Artist’s Viewfinder app is now available on the App Store. It took quite a bit longer than I first planned, but if you look at the sheer number of new stuff, you’ll understand why. More work went into this update than it took to develop the original version 1.

I wrote about the black & white mode and exposure compensation, and the question of RAW capture in former posts, now it’s time to reveal everything else. I’ll touch a few new things in this post, and highly recommend to take a look on the complete list in the release notes. And pay attention to the “Changes” section.

Quick Control Screen

The are a few subtle visual changes to make it less cluttered, and to make room for two new icons. The half dark/half light icon in the upper right toggles black & white mode. The 2x icon switches to the telephoto camera if you have an iPhone 7 Plus. The telephoto camera and wide converter use are mutually exclusive (as one would logically expect).

Icons for parallax correction/shift simulation and aspect ratio changing are now white when a non-default value is set for these (in the above example I set the 5DS R virtual camera to 16:9 aspect ratio).

Album -> Catalog

We had to rename the Album to Catalog to avoid a name clash with the thing that Apple calls an album in the Photos app. Now ours is named Catalog, since it would be extraordinarily hard to convince Apple that they should change…

And while we are talking about the Catalog, there are performance improvements here and there, meaning that an update may be required to the new format. The app automatically detects if this is the case, and will update the Catalog automatically.


This is a free update for existing Mark II Artist’s Viewfinder owners. New user can purchase the app from the App Store.

We offer upgrade bundles for former Viewfinder Basic/Pro/Cine edition owners, so they can upgrade for a reduced price.

The Viewfinder Handbook was also updated to cover all the new features.

Custom Wide Converters in Viewfinder 4.7

My Mark II Artist’s Viewfinder app has a unique feature from day one. Something that no competitor managed to copy: real-time distortion correction for wide converter lenses. In the past distortion correction was available through the profiles we made for all the wide converter and device combinations the app supports. Creating these profiles involves tedious measurements, and of course a purchase of each and every converter lens and iPhone/iPad we support.

The profile approach was good a few years ago with a limited set of converters on the market, but these days you can find at least a dozen different converter lenses at online retailers. This, together with the product lineup splits Apple already implemented with the Plus phones and Pro iPads, renders the previous modus operandi financially unsustainable.

So we decided to address this situation in a way that is beneficial for both our users as well ourselves: by allowing users to create a custom wide converter. And of course we do support simple distortion correction with this! Being a simple correction, it does not always produce the almost perfect results the profile-based approach is capable of, but as you’ll se in the examples later on, very capable nevertheless.

We’ll continue to support the profile-based approach for existing combinations, but will add new profiles only if:

  • we already have the converter and the device in the lab, or
  • we receive several customer requests to support a converter – as it was the case with the Moment Wide lens, or
  • we cooperate with the converter’s manufacturer.

OK, with all that said, let’s see how it works. Once you select Custom for the wide converter, a new menu item – Custom Converter Setup – will appear on the menu.

cwc-setupTapping it will bring up the converter setup screen that you can see on the left.

You can set the converter lens’ actual conversion factor with the first slider. Since this is almost always different from what the manufacturer says, you’ll definitely need to fine tune it for your actual phone (since the conversion factor also depends on the phone’s lens as well as the distortion correction amount – be prepared for a little trial and error). We support converters with factors between 0.45 and 0.7.

The second slider is used to specify how much distortion the converter lens has. It is an arbitrary scale from 0 to 30, zero meaning that you will not want to correct the distortion (suitable for well-corrected lenses such as the Moment Wide).

The setup procedure

Here’s how I recommend to do the setup. Set distortion correction first (if needed at all). I’d recommend 15 as the starting point for 0.65x-class lenses and 20 for 0.5x-class lenses. Check how the main screen looks, and watch for overcorrection in the corners. In case you still have barrel distortion, go back to the menu, and increase correction. If the corners are overcorrected, back off a little. A tiled wall, a window or a tall building are good test targets.

Once you’re happy with the correction, mount the phone steadily, turn off Wide Mode, and set the main screen so that you have some objects or markings at the edges of frame lines. Now turn on Wide Mode and check whether the objects/markings are still at the frame lines. Go into the menu and adjust the conversion factor if not. Repeat until you are satisfied with the result.

You can create only one custom wide converter, so it is advised to take note of the parameters in case you need to restore them later.

Correction examples

Walked up to Hallgrímskirja in Reykjavík to make some examples with my iPhone 6s Plus and two olloclip converters. Here is how the 4-IN-1 Wide lens looks with no correction.

olloclip 4-IN-1 Wide on iPhone 6s Plus - No Distortion Correction

olloclip 4-IN-1 Wide on iPhone 6s Plus – No distortion correction

As you can see below, this lens has a simple spherical distortion, which can be corrected almost perfectly with the custom converter setup. My experience is that most 0.65x lenses behave the same way and would only marginally benefit from a profile. Note that I set the conversion factor ad-hoc in these examples, so you may see some discrepancy in frame line positions.

olloclip 4-IN-1 Wide on iPhone 6s Plus - Custom wide converter with distortion setting 13

olloclip 4-IN-1 Wide on iPhone 6s Plus – Custom wide converter with distortion setting 13

Now to the olloclip Ultra Wide. Distortion is huge, and without correction renders the lens pretty much unusable for viewfinder purposes.

olloclip Active Ultra Wide on iPhone 6s Plus - No distortion correction

olloclip Active Ultra Wide on iPhone 6s Plus – No distortion correction

And this is how it looks with the custom wide converter’s correction. You see some mustache-like corners as the simple correction is not able to eliminate complex distortions (which profiles can do), but the lens becomes usable.

olloclip Active Ultra Wide on iPhone 6s Plus - Custom wide converter with distortion setting 22

olloclip Active Ultra Wide on iPhone 6s Plus – Custom wide converter with distortion setting 22

Just like with profiles, the simple distortion correction works only with wide and ultra wide lenses – not with fisheyes.

When will this be available? The feature is currently in testing in version 4.7, and is planned to be released later this summer. In the meantime, comments are welcome.

The updated app is now available for download.

Artist’s Viewfinder 4.6 Available

iphone_se_wideconvThe latest update to the Mark II Artist’s Viewfinder adds complete support for the iPhone SE.

This means two things. First, we’ve measured the angle of view of the SE’s camera. Second, since the SE takes iPhone 5s cases, we’ve created a distortion correction profile for each and every wide converter that we support on the 5s. You see the complete list on the left.

As usual, we’ve added a bunch of new cameras to the app’s database. I’d encourage you to take a look on the release notes for the detailed list.

Version 4.6 is a free update for existing Mark II owners. Users of former Viewfinder Basic/Pro/Cine editions can upgrade for a reduced price.