Focal Length Equivalents

Fri, 04 Jan 2019 15:56:47 +0100

Between Christmas and New Year’s – or “between ze days” as we say in Germany – I worked on a little project: Focal Length Equivalents, a website that let’s you look up focal lengths of different film- or sensor-formats and find its equivalent to the 35mm/full-frame format.

Here’s some more explanation from that new site:

Like a lot of photographers, you might be familiar with focal lengths in the 35mm/full-frame image format and what field of view that focal length represents (24 mm = wide angle, 50 mm = “normal” etc.). Different formats, however, require different focal length lenses to produce an equivalent field of view.

With this site, you can look up these focal lengths and their 35mm-equivalents.

For example, when I bought my 6x9 camera, I wanted to know what its lens’ 110 mm equivalent field of view is in the 35mm format – because that’s the format I’m most familiar with. And when looking up information like this I always end up looking through some old forum threads, if I don’t want to calculate it myself (which I never did).

That’s why I built this little utility, which calculates it for me and saves me the search. Check it out!

The UI

The UI is a table that dynamically updates as you move a slider. That slider is an HTML input element of type range.

My idea was to create a super-simple interface that’s easy to use on both mobile and desktop – i.e. with a touch interface as well as a mouse/trackpad. There’s nothing to type into a field and no button to push to recalculate. Simply move the slider.

Another benefit of this is, that you are always comparing all formats at once. No need to select or otherwise “activate” a specific format. You simply look at the row of the format that interests you to compare (tip: you can tap/click on a row to highlight it for even easier visual comparison).

Drawbacks

A drawback of this UI is, that the slider is somewhat fiddly to operate. And it’s a not very precise UI element, either. I might be able to make it less fiddly by creating a custom design for the slider. But the imprecision will always be there I assume, especially on smaller screens where the input’s values are spread across less horizontal space. I limited the focal lengths you can compare to mitigate this issue at least a little – but this is yet another drawback itself.

This is the MVP

This version is a MVP – a Minimum Viable Product. There’s quite a few things I have in mind to improve the UI or better communicate each format’s dimensions (which are the base for the calculation), and also add more formats. But I think it’s already quite useful, and that’s why I’m making it public right now.

If you have any feedback, let me know!

Daniel Pietzsch

Focal Length Equivalents

The UI

Drawbacks

This is the MVP