There have been a lot of complaints about Tamron with “strange focal lengths” and their line of zoom lenses for Sony. 17-28mm, 28-75mm and now 70-180mm. There are also some complaints about the f/2.8 lenses.

With the zooms, they are unusual focal lengths. I think most of the talk will be spent focussing on the missing focal lengths than what is right, and there is a lot Tamron is doing right.

So firstly, lets focus on why you would want to lose 4mm on your 28-75, 7mm on your 17-28mm and 20mm on your 70-180mm?

To understand that, we have to understand that lens design is all about compromises. When you create a lens, there are multiple factors that go into lens construction:

• size
• weight
• focal length/zoom
• aperture
• sharpness
• construction
• autofocus
• cost

If you want a prime that is small, edge to edge sharpness wide open, well constructed, autofocus and has an aperture of f/1.4, that is going to cost a lot. Sony could probably make their 70-200 f/2.8 a lot more compact than it currently is but it may $10,000 for the materials required to make it that way.

The problem with consumers is they want everything. They want a lens that should cost $10,000 but they want to spend a $1,000 and that is where the compromises come into play.

If you adjust any of the above criteria, one of the others will have to change to absorb it. So if you want to reduce the cost, the size, construction or sharpness may suffer, either individually or all.

That also depends on how much you reduce the cost. In the case of Sigma as an example, they sell lenses that are half the price, but offer great construction, sharpness, wide open apertures but they compromised on size.

It was a smart move by Sigma, a large portion of the photography population want the performance and sharpness of a Sony G Master and they get it at half the cost, with size or weight being the compromise. If you only have $1000 to spend and the G Master costs $2000, more often than not, that’s acceptable.

So how does this relate to Tamron? Tamron’s strategy is a little like the success of Fujifilm’s Fujicron range. A large amount of the people who bought into mirrorless did so because of the compact size. The problem is they want size and quality.

There are two ways to deliver size and quality:

• Reduce the aperture to f/4 for zooms or f/2.8 for primes
• Reduce the focal lengths (for zooms)

Sony has already produced a 16-35 f/4, a 24-70 f/4 and a 24-105 f/4 so doing the same thing means competing head on with Sony. There is also the stigma attached to the f/4 lenses as the poor cousins.

Tamron wants the people who consider size and image quality to be critical and there are a lot of them out there. Tamron also want to limit the amount of competition they have available which is exactly why they started with the 28-75 and not the 17-28.

On the prime front, by focussing on the f/2.8 primes, if they can produce smaller primes which are still high quality leaving Sony users in a position where they can buy a set of lenses for their Sony’s that are the same size as the APSC Fujicrons, the same optical quality, but still have the benefit of full frame with stabiliser. That isn’t a bad selling proposition for users looking at Sony over Fujifilm.