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how fast is the F1.4 28mm

Discussion in 'Lens Lust' started by Scott Sherman, Apr 23, 2005.

  1. Hi all,
    I am trying to get a fix on what i gain by adding a 28mm f1.4 lens to my kit.

    Using a hypothetical, If I use a 17-55/2.8 lens to take a photo under somewhat dark ambient light and the 17-55 is set at the lowest f stop, f2.8, making the correct speed for exposure, 1/60 sec. How much faster might the same exact shot under the same ambient lighting be if I had a 28mm opened to f1.4? I would love to hear from someone who could actually conduct this experiment especially with examples.

    Also, as a side issue, I have heard that the wider the lens, the more light emited at the the same aperture, such that... a 85mm f1.4 would be correctly exposed at 1/60 sec, while in the same ambient light, a 28mm set at f1.4 and (guessing here) say 1/125 sec would yeild the same exposure. Is there any truth to this, I am not sure of the validity of the poster who made this statement. It was not at this forum.

    Thank you for your responses.
  2. Scott,

    As you know, f/1.4 is 2 stops faster than f/2.8, so if you shoot the exact same scene (at the same focal length), and assuming the rounding errors of the actual specs (the 17-55DX f/2.8 appears to be f/2.83) are compatible, your shutter speed would be 1/250 or thereabouts. But you already knew that. :lol:

    I think your first question is loaded by the second question, which I think is true in practice, but only because of what is in the field of view, on average. The wider the FOV, the more likely you are to have an overall mid-grey exposure (in matrix meteing). There are of course tons of exceptions to this: if the subject is so uniform that it does not vary in its luminance when zoomed in or out, then it shouldn't make a difference: a large brick wall from a distance (where the brick detail is averaged), or a large grey card come to mind.

    However, if you pick a darker than average spot on a subject within a wide FOV scene and zoom in on it, the proper exposure of that zoomed in image, might need more light... hence less shutter speed. Similarly, if you pick a lamp (in a scene with a wide FOV) as your subject and zoom in on it, you'll probably need to increase your shutter speed to not overexpose it...

    On top of all of that, of course a wide angle lens can be hand-held at lower speeds too, because of the lesser magnification of the image shake... which in turns can yield more keepers at even lower speed. I think (don't quote my failing memory) that Ron Reznick showed pics with the 28 f/1.4 that he hand-held at 1/4s, and were so very sharp! ;-)

    Take all this with a grain of salt, and experiment. :)  :D  :lol:
  3. Phillipe,

    First thank you for your face saving words, I'll just say, sure I knew that and let it go at that. :oops: 

    Thank you for your very well thought out and articulate explanation. I don't have access to one in my immediate vicinity and I look to real world users for feedback. I give real world evaluations equal or greater weight than the pro reviews in some ways and try to extrapolate that to my needs/wants and style of photography.

    I tend not to like to go into camera shops when I don't think I will buy the thing I am looking at out of respect. I buy big ticket items through discount houses like B&H and most local camera stores around me are not that big and would not have that exotic of a lens in stock anyway. The bigger photo shops are a bit of a drive on California freeways and I am sadly short on time that with gas prices makes this a very desirable way of investigating.

    So thanks again Phillipe for your patient and eloquint response.
  4. Scott,

    Sorry. I didn't mean to experiment by actually trying a 28 f/1.4 lens. You could try the premise that a lens at the same aperture yields a higher shutter speed at wide angle than it does zoomed in, with any fixed aperture zoom you have in your arsenal, be it a 12-24 f/4, 17-55 f/2.8, 28-70 f/2.8, 70-200 f/2.8 (it's harder with longer focal lengths though).

    I assumed that you have one of those... but perhaps, this is where I was totally wrong! :oops:  ;-)
  5. Phillipe,
    I do get it, thanks again. I guess the bottom line is the 28/1.4 is a great lens. I am on the fence and contemplating getting one and just needed a slight nudge to push me over the edge. I guess you could call this a nudge.
  6. MontyDog


    Jan 30, 2005
    #1064 - You have an error in your SQL syntax;
  7. Not to burst your bubble but the 28 1.4 is not the sharpest lens around. In fact I get a bit worried when people say it's the sharpest in their bag. I never found my 28 1.4 to be *very very* sharp and just recently I stumbled on a Nikon site with all the charts. This proved indeed what I thought long ago: The 28-80G is sharper at 28 then the 28 1.4... I looked like a fool on Dpreview some 2 years ago when I said that but here it is:

    28 1.4

    28-80G 3.3-5.6

    Let's not forget this is only about sharpness. The colors, contrast, Bokeh and handling is all a dream with the 1.4 :) 

    Now, also on the good side: the 28 1,4 is incredible simply because it's made for those impossible occasions, which brings it on top where every zoom will fail miserably :!:

    Pictures like this are unthinkable without that lens and this is why 1000-1800$ become measly once you start shooting in unthinkable and priceless situations.

    Please note this was shot at dawn, Iso 800 (or even 1600, doesn't show on exif), 1/50th@ f1.4 ... I think this picture sums this lens up all around... :) 

    Subscribe to see EXIF info for this image (if available)
  8. My bubble is still intact. I didn't buy it because it was the sharpest lens in the store. I bought it because it could go where normal lenses could not and still give a very sharp picture.

    I'm curious, what is the story behind the picture you posted above?
  9. Yes, and the reason you bought it for is worth every penny.

    THe story is pretty simple: I was asked to exhibit some of my work and I just decided to refresh all my collection and while I was in eastern Europe I visited some remote Gypsy villages. Was a great experience. Not my first time but I always look out for the next.

    I also learned (don't know if this is urban legend) throughout my escapade(s) in the deep that the Tzigan people cannot contract aids and not a single case has ever been reported.
    Now don't flame me with facts (if they exist) as I really want to keep this "truth" naively into my mind :)  ...
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