24-70 at 2.8

[elliot1]

<p>Peter, perhaps we are splitting hairs... so I will concede that if you make an 8' or 10' long print of an unprocessed raw image, you may see a minuscule difference from f2.8 to f4, but certainly not like the OP's sample images which shows a noticeable difference.</p>

 

[n_s6]

<p>I'm my experience f2.8 is softer than f4 and I can see that softness in Eliott's example as well. </p>

<p>The examples of the plant to me look like different exposures, which could bring up the apparent contrast which looks like it's sharper, not to mention that f4 is sharper and can also correct a few 1/1000 if not focused on the exact same spot as f2.8<br>

I'd recommend taking a picture of a flat target, maybe a paper calibration one, you can download off the web. Make sure as you adjust the aperture to adjust the shutter speed so that the exposure remains the same.</p>

<p>I have found with liveview:<br>

1. af micro adjustments have no effect, and<br>

2. the actual AF square in LV can focus on different parts of the image, within the little square. If you have a target that is at an angle, the LV will autofocus sometimes on the top part, sometimes on the bottom, but within the square boundaries. You can adjust the size of the square but regardless it will affect the focusing and with the D800 I found a 1/1000 of an inch will make a difference.<br>

I recommend also taking several shots of a flat target well lit at f2.8, LV autofocus each one separately, followed by exposure change with f4 and several shots again to ensure some consistency</p>

 

[photomarche]

<p>N S,<br>

thanks, I too have noticed in Elliot's examples that f2.8 looks softer.<br>

The 24-70 is my first and only pro grade glass and maybe I have very high expectations. Nevertheless I will do more testing following your advices in details.<br>

Thank you all for taking your time to answer.</p>

<p> </p>

[elliot1]

<p>I took a controlled test, with flash, MF, same ISO (100).</p>

<p>These are 100% crops. This is the center of the frame where I focused on.</p>

<p>I maintain that pro Nikon glass is <em><strong>just as sharp</strong></em> wide open as when stopped down</p><div></div>

[elliot1]

<p>duplicate deleted.</p>

[elliot1]

<p>I am having trouble uploading. I will try again tomorrow.</p>

[elliot1]

<p>F4 crop</p><div></div>

[elliot1]

<p>Here is a side-by side comparison of the center of the frame.</p><div></div>

[elliot1]

<p>My conclusions, if you shoot RAW and do absolutely no post processing, perhaps someone printing a 10' wide poster looking at the images from 6" away may see a minor difference between f2.8 and f4, but for the typical photographer making typically sized prints, you can shoot at f2.8 and expect great shots.</p>

[Peter_in_PA]

<p>Your test is not a flat piece of art, and it therefore shows focus irregularities more than anything else, Elliot.</p>

<p>Your claim is in contradiction to everything I've ever read in basically every review of basically every lens I've ever researched... all of which say that basically every lens needs to be stopped down for max sharpness.</p>

<p>But I'm gonna leave it alone.</p>

[Landrum Kelly]

<p>My own experience has been that with pro glass the difference between wide open and stopped down a bit is negligible. With cheap glass, the difference can be considerable.</p>

<p>Practical conclusion: Pro glass can typically be used wide open with no<em> perceived</em> loss of quality in real world results. On one hundred percent (100%) crops, one will detect very slight improvements upon stopping down, but this is often so negligible as to be of no real practical significance. For crops, however, it might be--it depends on just how severe the crop is.</p>

<p>With cheaper glass, one often can notice the difference in quality, and stopping down is often necessary in order to get acceptable results. This will often mean that using a tripod is not optional: a tripod will be required.</p>

<p>Practical corollary: Pro glass gives another stop (or sometimes a bit more) without any perceptible loss of quality for most practical applications. <strong>It is that extra stop or so that we are paying for.</strong></p>

<p>Is it worth the extra cost? That is a very personal call. The extra stop or so will mean that a faster shutter can be used, and that means that the pro glass can often get a very good shot without a tripod or other even more heroic measures.</p>

<p><strong>Caveat</strong>: My conclusions are based primarily on having used Canon EOS lenses from 2006 to 2012, but I have seen nothing since switching to Nikon which would impel me to change these conclusions. That said, my stable of very good Nikon lenses is still very small.</p>

<p>--Lannie</p>

[Landrum Kelly]

<p>Qualification to what I just wrote: Stopping down to f/8 on the D800E is not "stopping down just a bit." At f/8 there <em>will</em> be noticeable data loss from diffraction.</p>

<p>Second qualification: What might be true (regarding softness) at one focal length on a zoom will not necessarily be true at all points on the focal range.</p>

<p>--Lannie</p>