f/1.4 versus f/1.8 in Lenses of the Same Focal Length

[peverall_dubois]

<p>Given two lenses of the same focal length (say 30mm)<br />but two different apertures: 1.4 and 1.8.<br /><br />On what condition/shooting type, the f/1.4 is preferred to the other or vis versa,<br />apart from subjective preference of more blurred background?</p>

[dave_s]

<p>(i) The 1.4 passes 65% more light, so on an SLR the focusing screen will be brighter.<br>

(ii) The 1.4 enables sharper focusing, because depth of focus is less.<br>

(iii) One or the other lens may have different optical properties. All other things equal, slower lenses are often said to be 'sharper'. On the other hand, for some lenses, like the Canon FD I know about, most people would say the 1.4 makes the better image.<br>

(iv) The 1.8 will be smaller and lighter.</p>

[Matt Laur]

<p>Remember also: it isn't just the <em>degree</em> of the blurred background if you're shooting each of those lenses wide open - it's the <em>quality</em> of the blurred background. Likewise what each lens does in the way of chromatic smearing, flare, contrast, etc. <br /><br />As a very general, very loose rule: most of those f/1.4 lenses are more expensive, and made for a more demanding user. The extra bit of light is only part of what you're buying. There are frequently a number of areas in which such lenses - even you never use them wide open - are going to be preferred.<br /><br />For example: I've got a 50/1.8 and a 50/1.4. I sure like how small and light the 1.8 is, but it simply doesn't produce anything close to the same quality. They're very close once they're each stopped down a ways - at least in terms of sharpness - but there are big differences in contrast, bokeh, etc. So, the larger, heavier 1.4 is on the camera much, much more often - even if I have no intention of shooting wider than f/5.6.</p>

[scott_murphy_photography]

<p>Since I have maybe shot a 50mm lens (I have a 50mm f/1.4 Nikkor) about a dozen times in the last 35 years, the greatest advantage, at least for me, of the f/1.4 over the f/1.8 would be about a half stop brighter viewfinder image. As far as resolution and flare protection goes, that is dependant on the manufacturer. Some of the f/1.4's are sharper and contrastier than the f/1.8's but the real question is how much do you have to enlarge the image to see to see the differences? In most cases, up to 11 x 14, you probably could not distinguish the two lenses three stops (usually optimum for a lens of this kind) down. The other advantage is cost, which can be significant. Is that extra 1/2 stop worth a 50% or more increase in price? In most cases I would say no.</p>

<p>Then there is always the "cool" factor. The f/1.4 has a lot more glass up front, so it definitely wins in the "cool" looking department! :-)</p>

[eric friedemann]

<p>Depending on the manufacturer and lenses compared, there may be other advantages to an f/1.4 lens, as well. While I've never owned a "30mm lens," I have owned the Nikon 85mm f/1.8 AF-D lens and currently own the Nikon 85mm f/1.4 AF-D lens:</p>

<p>1. The 85mm f/1.4 AF-D lens is built like a tank, with a terrific Parkerized finish. The f/1.8 lens is nicely built, but the f/1.4 just has a little better fit and finish.</p>

<p>2. The f/1.4 lens is sharper. The 85mm f/1.8 AF-D is no slouch, but the from f/2.8 down, the f/1.4 is just brutally sharp.</p>

<p>Nikon doesn't make a 28mm f/1.8 lens, but I've owned a 28mm f/2.0 AI-S lens and just about every 28mm f/2.8 SLR lens Nikon's ever made. Currently, I own a 28mm f/1.4 AF-D ASPH lens and comments 1. and 2. above hold true in this focal length as well.</p>

[keith selmes]

<p>I have a Canon Ef 50/1.8 MK1 and Zeiss (Contax fit) 50/1.4 Planar.</p>

<p>The 50/1.8 is lightweight plastic and AF, very convenient to carry around, but not too robust. Very sharp stopped down a little but wide open its a bit soft, and not really a good soft either, just scruffy.<br>

Bokeh is OK, but no more than OK.</p>

<p>The 50/1.4 is sharp wide open, very superior bokeh, very solid build, but heavy. And of course no AF, although the MF adjustment feels really good. It costs about half as much again as the 1.8, bearing in mind both were bought used.</p>

<p>So really, the 1.8 will go on a long walk, go happy snapping, but seldom get used indoors, whereas the 1.4 might get left behind unless there is a need for wide open shooting or nice backgrounds.</p>

[conrad_hoffman]

<p>My only experience is with older 50mm Nikkors. The f/1.8 was always considered equal or a bit better than the f/1.4, but the cool factor and the extra bit of light convinced everybody who could afford it to get the f/1.4. I've actually had an Ai f/1.4 that was pretty flat and disappointing. Purchased it new. Much better luck with a mid '70s AiS f/1.4. All that said, I did a comparison of everything near 50mm I could lay my hands on, including the 55mm f/2.8 Micro Nikkor, and cheap "E" versions too. Pointed at the same subject, under the exact same lighting conditions, the differences between them mostly evaporated. I suspect sample differences are the big thing to watch for. Buy whatever suits your needs in terms of speed and budget, test it, then don't lose sleep over it since the quality of the images will depend on you, not the lens.</p>