New Olympus 17mm 1.8

Started Mar 7, 2014 | Discussions thread
Mark Chan Senior Member • Posts: 1,717
Re: New Olympus 17mm 1.8

My apologies if I have insulted you.

Consider the following statements:

The 20mm f1.7 has slow AF.

The 20mm f1.7 has slow AF in the 0.2-0.75m focus range.

The 20mm f1.7 has acceptable AF in the 0.75m to infiinity range. For ordinary S-AF and Practical Purposes.

The 20mm f1.7 AT 0.75mm to infinity range has comparable AF with the 12mm F2

The 17mm f1.8 has comparable AF with the 12mm F2

The 20mm f1.7 has comparable AF with the 17mm F1.8.

What impression does the reader get from the above statements? How do they diverge / differ?

Using Petka Potka's information on the AF speeds for 12mm F2 and 20mm f1.7: 0.74s vs 0.87s.  Based on this the 12mm f2 is 17% faster than the 20mm f1.7.

I frankly cannot fathom how '17% faster'  means comparable.  We can argue all day but I have exhausted myself as regards this thread.

Can we say a runner that runs at 11 seconds be comparable to one that runs 17% faster?  But ofcourse, we are discussing fractions of a seconds, so for 'all practical purposes', this is a moot point.

Define ordinary S-AF use; Define practical purposes.

The term 'practical' is subjective.

From my experience with the lens and YES, its experience and not TEST, and practical purposes; the lens is slow. it acceptable for taking pictures of adults posing, candid pictures of people and landscape.  It is not acceptable for taking pictures of kids running around at close quarters (well I'll leave that subjective), or trying to catch a bicycle cycling past a lovely beach or background - unless you STOP the aperture down; Or to catch an athlete running by.

Nor is it acceptably fast for sightseeing when you may take a picture of a flower at close range then turn around and try and snap a picture of your kid spinning towards you.

In light of that, when someone 'asks' if 17mm AF is faster than 20mm, what should be the simple and clearest answer?

Yes it is. Call a spade a spade.

Not 'comparable'; not 'for ordinary use its much the same'; not for 'all practical purposes'.

Just a simple, it is. We can add 'but then I have been able to adapt my photography such that its not an issue.'

This way, you are not misinforming people into thinking that the 20mm lens can do what it cant.  A newbie into photography would think that he had a bargain for the 20mm and only later realized the lens was not 'quick enough' for his needs; because somehow, for his 'practical purposes', he would find it slow.

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