Do you need the "best" lens

rsn wrote:

Valdai21 wrote:

What matters to me is good enough

The "good enough" concept is well known in another hobby I participate in, its kind of a "devil in the details" and you can get bogged down in technical details and over prep. There is also another concept in the hobby which I have adapted to photography. Does an image have a "Wow!" factor. If a photo is a Wow! photo, it can get away with many sins.

The ability of a lens to collect light is an interesting topic for me, an f1 in a 1.5 crop sensor is really an f1.5 lens. Many understand one has to apply the crop factor to lets say a 100mm lens - which becomes a 150 lens - but don't realize the crop factor also applies to the f number as well.

And interestingly lens from the same and different manufactures, all with lets say a f1.4 build do not collect the same amount of light. The movie industry ran into this problem when lenses that were in theory the same f1.4 but each lens collected more or less light than other lenses used that were an f1.4. So they created the T number which measure how much light is hitting the sensor. Saying a lens is an f1.4 is a build description. Many feel the photography industry should adopt the T number instead of or along with the f number. Here is a short video to explain the difference:

https://www.youtube.com/watch?v=B2tkjcoU55Y

If one is looking for a fast lens, lets say thinking of purchasing a f1.4 factor lens then it would be helpful to know the T stop when comparing lenses, wanting the "fastest" lens. So what is faster, the Canon 50 1.4, Sigma 50 1.4, Tamron 50 1.4, etc.

And quality bokeh is not only a function of the f number, lets say f1.4. It is also a function of the build of the lens, I prefer more rounded blades, preferably 9 or more but 7 can bring happiness as well. My Canon mk 1 50mm f1.8 had 5 non-rounded blades and didn't provide as great a bokeh as my Sigma 50 f1.4 9 rounded blades. The Fujifilm 14 2.8 has 7 rounded blades, the 35mm 2 has 9 rounded blades, and the 50 2 has 9 rounded blades to produce decent bokeh.

To the person who pointed out blur is different than bokeh, I understand this and agree. I had a hard time finding an image with decent bokeh with the 14 f2.8 lens as almost no one takes those kinds of shots, almost all are travel or landscape. At least there were almost no bokeh shots on the Flickr Fujifilm 14mm f2.8 page.

F/1 is F/1 on any sensor.  On APS-C an F/1 lens will have equivalent depth of field as a F/1.5 lens on full frame.  A F/1.4 lens has a DOF equivalent of F/2.1