Focal length 35mm equivalent, but not F-stop?

Started Jul 24, 2014 | Discussions thread
Gerry Winterbourne Forum Pro • Posts: 16,451
What ordinary people want

Chikoo wrote:

All camera manufacturer when they publish technical specification of their camera lens publish the focal length and it's equivalent in 35mm. But the same is not done for F-stop. Why?

Ordinary people just want to take photos. Most of them know absolutely nothing about photography and nothing relating to 35mm cameras means anything to them. Quite a few, though, have some former experience with 35mm, or access to people with such experience.

I'll start with APS-C because that was the first widely used sensor size. In use an APS-C DSLR was, and is, very similar to an SLR , with one major difference - the crop factor. I was caught out by this (my fault for insufficient research but caught I was). Focal length has various effects but the one that most obviously affects users who know about 35mm photography is the FOV so stating FLs in 35mm equivalent as well as the actual FL is a simple courtesy to buyers.

The same thing applies to users of other sensor sizes and camera types: either FL means nothing to them or they have some knowledge about 35mm FL/FOV. So that information is useful. But anything beyond is superfluous: you only have to read the Beginners forum here to know how few newcomers understand DOF as a concept, so what earthly use to them is data on equivalency?

On the other hand, anyone who knows - and cares - about such things is able to work them out so the information isn't needed.

Ditto the noise equivalency mentioned elsewhere in the thread: get into that and you should also be asking why camera makers don't publish data on the noise performance of all cameras. Even at the same sensor size, why don't we see noise data to allow us to compare a D700 with a 6D with ...? Because without that it's pointless to look at a P&S noise performance v a specific other camera.

So what makers give is a compromise between completeness and confusion.

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First camera 1953, first Pentax 1985, first DSLR 2006

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