For a period of a few years, the lens and camera manufacturers were drunk on the idea of even smoother bokeh than normal. It was so much so that it ended up cutting down the amount of light a lens output. Some folks call it a smooth transition lens while others refer to the specific optic in the lens as something along the lines of “DS.” And for a while, it seemed like every camera manufacturer had a lens like this. But then smooth transition focus lenses of all sorts all disappeared. Why?
To be more specific about this trend, Panasonic, Leica, and Sigma never made a lens like this. Nor did Olympus. Oh yeah, and Nikon didn’t do it either. But Canon, Sony, Laowa, and Fujifilm made variants of it.
So what were these lenses, For the ease of this article and naming, we’re going to call them Smooth Transition Focusing lenses. These are lenses with a special glass element inside of them that smoothes the bokeh out even more. That sounds really nice — but at times, it was at the cost of around a stop of light. In the case of the Laowa 105mm f2, the T-rating of the lens was T3.2. That means that the lens suffered from even more than f2.8 in terms of light loss.
And quite honestly, that annoyed photographers a bit. It means that you really couldn’t use it with natural lighting all that much unless you raise your ISO into ranges that truly didn’t make sense. For example, why would you need to raise your ISO to 1600 when shooting wide open in daylight? Where these lenses really prevailed, however, is when a photographer used off-camera flash.
On top of that, these lenses often had longer focal lengths, so you’d need to shoot with a faster shutter speed. A good example is Laowa’s 105mm f2.
The reason why you’d need to use a strobe off-camera is because you have to compensate for all the lost light without raising your ISO levels up. If a photographer raises their ISO up, then they lose image quality — and I’m not talking about the added grain. Instead, what I’m talking about is color loss. In general, most modern day cameras really begin to lose their full color abilities after ISO 400 with many suffering significantly at ISO 6400 and beyond. But if you shoot with a lower, more film-like ISO, then you don’t have that issue as much. Lightroom and Capture one can do a good job with ISO and color accordingly, but there’s only so much each of those can do.
Photographers could instead just use a CPL as Polarizing filters can make your images pop even more. What would’ve been ideal is if the brands put a circular polarizer within the lens itself and let photographers dial in the effect as they needed it.
