Source: Sami Paju, Olympus 17mm f/1.8 lens
These two lens might share almost the same focal length, but they have characteristics that make their usage different.
If you have difficulty choosing between the two, you're probably distracted by the advantages the the Olympus lens.
Alright, let's look at what they offer.
Olympus 17mm f/1.8 lens:
- With EXIF data
Voigtlander 17.5mm f/0.95:
- Faster at f/0.95
- Soft wide open
- Sharper when stopped down
- Physical aperture ring
- Manual focus
When it comes down to getting the picture, there's only one key differentiating point: The Voigtlander shoots at f/0.95.
The Voigtlander is made for shooting in extreme low light situations.
If you need to shoot at night, get the Voigtlander. The Voigtlander is almost 2 stops faster than the Olympus. For places lit by just lamps, the f/1.8 of the Olympus is oftentimes not adequate.
Just for example, say the threshold of unusable noisy photo is ISO1600 (or whatever), the Voigtlander will give you a less noisy photo because you can shoot two stops faster. So if you're shooting at ISO 1600 with the Voigtlander, it means with the Olympus you have to shoot with the usable ISO 6400. That's where the f/0.95 becomes absolutely necessary.
In other words, when you're in a situation that requires f/0.95 for the exposure, you will get no usable shots a f/1.8, assuming of course you've maxed out the ISO.
Yeah, the Olympus is cheaper, smaller, lighter, yadda yadda, yadda...
The resolving power, or even the bokeh or rendering, do not come into the argument at all. All those factors are not related to getting a picture.
Source: 夏天, , Voigtlander 17.5mm f/0.95