Why is f1.4 so important?

wildman · 03-14-2016, 10:55 AM

Originally posted by normhead

make narrow DoF a signature or your style.

ie a banality

**Alex645** · 03-14-2016, 11:07 AM

I've posted this in an earlier thread, and my critical focus is off in the f/1.4 and f/1.8 examples, but if you look at the bokeh in the out of focus background, you'll see that the f/1.4 is slightly larger. The quality of the bokeh (smooth flat discs in the f/1.4 vs. harsh round coronas or condoms in the f/1.8) is due to the lens design, not the aperture. These were all shot with an APS-C sensor.

But to me, the main advantage of the f/1.4 include:
a) the brighter viewfinder (1/2EV is 50%)
b) excellent sharpness starting at f/4 vs. f/5.6
c) the overall better sharpness and less CA (do a side-by-side comparison on dpreview of the same manufacturer's f/1.4 vs. f/1.8

The trade off is a huge bump in price. For anyone on a tight budget, just going from a kit zoom f/4-5.6 to an f/1.8 prime is gold. But if you've got the coin, the f/1.4 is platinum.

normhead · 03-14-2016, 11:13 AM

Originally posted by WPRESTO

New lens encourages me to take pictures, just to see what it will do. Not a total cure for inertia, but close.

Yes, for sure, getting a new lens is like getting a whole new perspective on the world. Especially if it's a new focal length. Everything old is new again.

aurele · 03-14-2016, 11:20 AM

Originally posted by normhead

So in answer to "Why is f1.4 so important?"
It's all about you. Is it important to you, or isn't it?

Originally posted by normhead

So, what I'd like to see is, what does this image look like at 1.7 or 2 or 2.4 or 2.8? While the above is a very nice picture, I have nothing to compare it with. SO as a non-1.4 owner, it leaves me with more questions than it answers. My first question would be, how would it have looked with my 70 2.8, which is my favourite portrait lens among the ones I own. But then, I tend to look for reasons not to buy lenses, and buy the least I can get away with, unless they are under $80, in which case I'll buy them just to play with them.

I have the DA*55/1.4, and i use it very often @f1.4. Not because i really ever want to. But because i need to

I'm not a crazy fan of bokeh, blur, softness and buttery. I just shoot quite often, friends, during party, clubs, competitions, and i have to use iso 3200/6400 with a 1/30 to 1/200, to get correctly exposed shots. Hence the f1.4 allowing me to get the shot.

But keep in mind 70% of my shoots are with the DA*55, on film and digital. It's the right lens for me.

But, everytime i can, i use it at f2 or f2.8 because i need a bit more of DoF

normhead · 03-14-2016, 11:30 AM

Originally posted by aurele

I have the DA*55/1.4, and i use it very often @f1.4. Not because i really ever want to. But because i need to ...

I just shoot quite often, friends, during party, clubs, competitions, and i have to use iso 3200/6400 with a 1/30 to 1/200, to get correctly exposed shots.

Now, to my old school mind, that's what ƒ1.4 lenses were made for.

**From1980** · 03-14-2016, 12:16 PM

Originally posted by Winder

Good AF systems don't really struggle with it. AF accuracy of the new mirrorless systems make it pretty easy. DSLRs with a mirror need to be calibrated to the lens, but with a good AF it should AF just fine. The AF in the K-5 was just not accurate enough for my F/1.4 85mm. The K-3 does a much better job. The Sony A7II with Eye AF lock gives you dead on AF at any aperture 99% of the time.

A great point made here. I'm wondering if the "soft wide open" comment many say about trying manual lenses is explained by reliance on the focus indicator in the viewfinder instead of true manual focus technique fine tuning image detail with a discriminating eye. Many users experience "manual focusing" may only be as valid as the accuracy of the AF system in use.

dtmateojr · 03-14-2016, 12:45 PM

Originally posted by LensBeginner

Jaggines is caused by stopping down, because when you stop down you move the aperture blades (or you move a stop on the lens and the camera moves the blades for you when you shoot, which ultimately leads to the same outcome)...

It is also related to lens speed, since they both impact the end result, and since old 6-blades lenses like the one I mentioned will generally have a round bokeh wide open, so you actually choose the speed at which rhe bokeh is round when you choose a lens of a given speed.

For instance, speaking of SMC-M, a 50/2 will produce a round bokeh wide open, just like the 1.7, but of course at a different f-stop
Knowing at which aperture one is likely to shoot, one can make the tradeoff between sharpness, bokeh shape, f-stop (speed and DoF) etc. in a conscious way.

...next time I'll probably write two or three time the text, since as soon as someone makes the mistake of leaving some basic thing implied on a forum, he's immediately "corrected"... jeez!

@Na Horuk
I brought up that example because, as I said, it's a lens I use all the time, and it is a phenomenon worth considering. I also have a DA 40mm XS, but I don't think I like it as much as the 50mm.

If one uses a lens with many and/or rounded blades, the phenomenon can be less apparent, but I'm starting to think that having rounded aperture blades (or lenses which are well corrected for various CAs) isn't necessarily something you would want... it's merely another of the many tradeoffs that you are forced to make in photography (see the interesting blog entries by Yannick Khong someone linked here in PentaxForums)

Obviously you haven't seen lenses with round aperture blades yet.

**WPRESTO** · 03-14-2016, 12:58 PM

For a short time I had a Steinheil 40mm f3.5 Cassaron, M42 mount, made for the Contax S. Tiny little lens that had an aperture with 10 curved blades. This optic has become somewhat of a collector's item, worth more now than when I got it or parted with it.

devouges · 03-14-2016, 01:31 PM

Originally posted by Marktax

Definitely worth discussion over a beer . . . . (SMC-A 50mm 1.4)

Over a beer ! ! ! ! Any time

**Just1MoreDave** · 03-14-2016, 01:35 PM

Originally posted by Alex645

...But to me, the main advantage of the f/1.4 include:
a) the brighter viewfinder (1/2EV is 50%)...

If you have an f1.4 Takumar, you can test this yourself. Put the lens on, A/M switch to manual, aperture ring to f1.4. Look through the viewfinder and turn the aperture ring until you see the brightness change. I see no change until j3.5* with my focus screen, no change until then. So I think this is not true for Pentax DSLRs, except maybe for ones with the EE-S focus screen.

A K-mount f1.4 lens with an aperture ring could be used by partially mounting the lens or using the green button.

*I'm not 100% sure how accurate my lens's aperture size is because I have had it apart a lot.