How do I evaluate a new lens against one in my bag?

[walter_strong5]

<p>Let's say I decide to get the 35mm f/1.4 lens and want to evaluate it against my 24-105 f/4 for overall sharpness. I'm think'n I'd set the camera on a tripod and shoot my neighbors's house at every f/stop with the 35mm and then duplicate the feat with the 24-105 set at 35mm. Blowing up small segments of the images at each f/stop from each lens and looking at them side by side should reveal any differences in sharpness and perhaps in contrast too. The 24-105 is an IS lens and therefore I should gain a couple of f/stops, however I'm think'n I should expect a SIGNIFIGANT sharpness advantage in the 35mm or pack it up and send it back. After all $1388 (Abe's of Main) ain't nuth'n to sniff at for a work'n boy. Am I on the right track here or do I need to take "Lens Evalualtion 101" at my local JC?</p>

[sheldonnalos]

<p>I wouldn't expect a SIGNIFICANT different in sharpness. The 24-105 is a darn fine lens. I've done this test, you won't see much difference in the center even at f/5.6 and at f/8 or f/11 they are about equal. For resolution you'll be getting the most improvement in the edges/corner of the frame, and it will be most noticeable at f/4.</p>

<p>What you really need to do is to shoot a bunch of shots of the subjects you normally like, but done so wide open and focused close. That's where the 35L shines - has a totally different look to it than the 24-105 at f/4 and 35mm. If you like the look of wide open apertures and a wide field shallow DOF look, then you'll see why the 35L is popular. If you're just interested in pure resolution, then I'm not sure it's worth spending that much over the 24-105.</p>

[walter_strong5]

<p>Thank you Sheldon, that's good information! Now, let me ask you this. The 35mm f/1.4 is about $1400 and the 35mm f/2 is about $300, that's $1100 stiffer for the L lens. Am I going to see a SIGNIFIGANT amount of difference between these two lenses shooting wide open and focusing close?</p>

[peter_j2]

<blockquote>

<p><strong>The 35mm f/1.4...and the 35mm f/2...lens. Am I going to see a SIGNIFIGANT amount of difference between these two lenses shooting wide open and focusing close?</strong></p>

</blockquote>

<p>Based on this tester (wide open and presumably close), yes. Especially in the corners including significantly more vignetting with the 35/2.</p>

<p>http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=121&Camera=453&Sample=0&FLI=0&API=2&LensComp=122&CameraComp=453&SampleComp=0&FLIComp=0&APIComp=0.</p>

<p>You will also see from the same tester little difference between the 24-105/4 at 35mm wide open and the 35/1.4 at f/4.</p>

[walter_strong5]

<p>Peter, thanks. More good info.</p>

[John Crowe]

<p>Make sure your subject has lots of fine detail to evaluate under magnification. I don't put complete faith into any of the on-line image samples. I believe you will find that the 35/1.4 L will outresolve both lenses in question and will also provide greater contrast and superior colour rendition, which actually can still help in digital imaging.</p>

<p>Having said that I hope you will be using the 35/1.4 L an awful lot to justify the cost difference over the 35/2. Are you using it as a standard lens on a crop body or for lowlight interiors on full frame?</p>

[sheldonnalos]

<p>Between the 35L and the 35 f/2 shot wide open and focused close... yes there are noticeable differences. I found the 35L to have better sharpness, color rendition and contrast and better background blur quality, and obviously will have shallower depth of field due to f/1.4 vs f/2. In my opinion, the combination of those factors makes for a more aesthetically pleasing photo.</p>

<p>Now whether those nuances are enough for you to justify $1100 is another question.</p>

[g dan mitchell]

<p>First, if you want to test "sharpness," and not your ability to hold a camera still, you must use a tripod. To eliminate other variables also use mirror lockup and a remote release. To avoid testing the cameras AF system rather than lens sharpness, you might use live view to focus if you have that feature on your camera. The, as you suggested, make a series of images at the sequence of apertures and compare.</p>

<p>But when you compare, keep a few things in mind:</p>

<ul>

<li>While the prime can produce "better" resolution than the 24-105, this will be most apparent at the largest apertures. The 24-105 can produce very sharp images at the 35mm focal length when stopped down.</li>

<li>The "betterness" that may be visible at 100% magnification may or may not play out in terms of differences in your final photographs - for a whole range of reasons: you need to optimized the rest of your shooting process in order to get the best sharpness, unless you print quite large (and are a skillful post-processor) the differences may be too small to notice, etc.</li>

<li>"Sharpness" is not the only difference between such lenses. The prime should provide better out of focus backgrounds (e.g. - "bokeh") at very large apertures, the prime will likely show less vignetting, etc.</li>

</ul>

<p>In the end, it is always important to ask why you wanted the prime. If it was just for "more sharpness," there is a good chance that you won't see much benefit from the lens unless you use it in a way in which the marginal sharpness differences are actually visible.</p>

<p>Dan</p>

[walter_strong5]

<p>Boy, lots of good input here. Thank you all.</p>

[jeffrey_c1]

<p>35mm 1.4 let's in 8x more light into the camera body. This is also good for low light conditions when not using a flash. At f/1.4, this lens is brighter than the human eye.</p>

<p> </p>

[steve_dunn2]

<cite>The 24-105 is an IS lens and therefore I should gain a couple of f/stops</cite>

 

<p>Only when shooting in a situation in which the camera does not have steady support (e.g. handheld or on a monopod). If you're using a reasonably sturdy tripod on a stationary surface, IS will not be useful with this lens. While the lens supposedly detects such a situation and locks the IS elements, it would have to take a bit of time to do so, and even once the IS elements are locked, the sensors remain active, consuming power and reducing battery life (which contributing nothing to your picture); therefore, you might as well just turn IS off.</p>

 

<p>In the specific case of a sharpness/contrast test, of course, if you aren't using a reasonably sturdy tripod on a stationary surface, or some other method of camera support which keeps the camera motionless throughout the test, then your test is just a waste of time. In your original question, you stated that you were going to put the camera on a tripod for this test, so it's clear that you already know this. Therefore, IS, as useful as it can often be in real-life use (and I've been an IS believer ever since my first IS lens over a decade ago), is irrelevant to this test.</p>

[steven_crist]

<p>Take the 35L and the 24-105L zoom and aim at a subject with both lenses set at f1.4. Oops - can't do that with the zoom. That's most of where the price of the lens comes from - fast glass.</p>