Standard lenses Compared; Canon 50mm 1.4 and 1.8, Minolta 50mm and 45mm MC and MD

<p>Mauro, thanks for the posts. The corner shots are obviously softer than the center shots with the Minolta, but I have a hard time believing that it's a typical result to find that the corner sharpness of the Minolta f/1.7 wide open is sharper than the center sharpness of a Canon f/1.8 wide open. I think this is just b/c of mis-focus. Too bad you can't try both lenses on the same camera!</p>

<p>Good point you made with the 12MP vs. 35mm film. Although a rigorous proof of your claim would be rather difficult. You'd have to compare the size of the smallest image-forming element on film vs. the size of a pixel on the 5D. This is hard with film b/c its response drops off with decreasing contrast. At worse, remember, Velvia can be only 5MP (for a full 35mm frame) @ 1:1.6 contrast.</p>

<p>While the proof may be in the pudding (your downsized 12MP image appearing sharper than the original scan), we shouldn't immediately discount the possibility that the 5D would still show the Canon lens' defects. Why? Take the 5D & the 5D Mark II side-by-side. The latter would be more prone to show lens defects b/c of its smaller pixel size, correct? However, if you were to downsize the 5D II image to 12MP, the downsizing algorithm may be better than the effectively averaging 'algorithm' the 5D would be using (it's <strong>one</strong> larger pixel might average <strong>two</strong> of the 5D II's pixels, is what I'm saying)... possibly rendering the 5D Mark II's downsized 12MP image as sharper than the 5D's 12MP image (which, of course, normally would be the case if the lens weren't the limiting factor).</p>

<p>Ok, I think I just got lost in my own argument.</p>

<p>What I was trying to say is that Steven F's observation that the Canon f/1.8 lens really is sharper than what you're saying might actually be more b/c your camera mis-focused, rather than b/c you have a higher resolution capture medium.</p>

<p>Debate :)<br>

-Rishi</p>

<p>I a quick test with my 40D today and the 50mm 1.4 and in some of the shots I was able to show better sharpness. Not a controlled test but it appears there is some variance on the AF on a 40D body as well.</p>

<p>Also the 40D (ironically as you were guessing) appeared to have slightly better performance on the cormers in one of the shots. Not sure what to make of it yet since I was as parallel to the target as I could....</p>

<p>Actually, that's not ironic at all. The 40D has a crop factor, which means it doesn't even use the sides of the lenses. So sharpness/light fall-off is much more visible on full-frame (digital & film) bodies than on crop factor bodies such as the 40D.</p>

<p>I was just saying that the larger the smallest image-capturing element (i.e. 'pixel' on a digital camera) is, the less it will show lens sharpness defects. See Ken Rockwell's <a href="http://www.kenrockwell.com/tech/full-frame-advantage.htm">'The Full-Frame Advantage'</a> .</p>

<p>Also the full frame (TMAX) showed better -marginally- performance at f1.4 than the center portion. Strange.</p>

<p>Mauro, I did the test on the Sigma 50 f1.4 EX on my 5D. I used this <a href="../learn/optics/">PDF test sheet</a> printed out on 8.5 X 11in paper. One print for the center and one for the edge. As I stated earlier I have split focus screen on the camera and it showed no difference between manual and auto. Auto focus had a little difficulty seeing the small text in the center of the sheet while it could reliably find the edge of the sheet if I shifted the camera to the left or right. So I put the lens in manual when I did the test (with the center focus point centered on the center test target). I started at 1.4 and worked up to 2.8. I will only post the 1.4 and 2.8 test since there was no change in resolution. In the following crops of the two tests I circled the smallest lines the camera could resolve as shown in the original raw. The center of the lens at 1.4 and 2.8 could resolve a line 1.5mm wide. The corner could resolve a line 2mm wide. The camera was 15.5 feet from the targets (that was the best I could do). </p><div></div>

<p>Sigma 50mm 1.4 EX (Corner target at 1.4).</p><div></div>

<p>Sigma 50mm 1.4 EX (center target at 2.8)</p><div></div>

<p>Sigma 50mm 1.4 EX (corner target at 2.8)</p><div></div>

<p>As you can see the corners are a little soft when compared to the center but its not a big difference in my mind. For some reason which I don't understand there was a difference in light levels in the room (exposure was set to manual). However I don't believe there was any difference. Sorry I didn't go any further than F2.8 but it is getting late and will be too busy tomorrow to do any more (photo club meeting). One of the best reviews I found of the Sigma 50mm 1.4, Canon 50mm 1.4, and Canon 1.8 are on <a href="http://www.dpreview.com">www.dpreview.com</a>. I will be interested in how you feel my results compare to your tests. I find it hard to read your test charts (that is why I use a ruler to measure the line width). </p>

<p>Oops, nevermind. Sorry. Disregard my comment!</p>

<p>Thank you very much Steven.</p>

<p>When you have time I would be interested to see how the autofucus performs.</p>

<p>There is some apparent light fall off on the corners.</p>

<p>Below is the comparison to the Minolta sized to match the 5D resolution and a quick levels to match your lighting. (It is the best I could do in 1 minute while I was getting ready in the morning). I hope it is somewhat what you wanted for comparison.</p><div></div>

<p>I'd say both (your lens and the Minolta) are excellent. I just wonder about autofocus.</p>

<p>As you will see in the next two photos there is minimal difference between the previous manual focus shots and the following auto focus shots taken at F1.4 on the Sigma 50 1.4. In the center it appears to have been slightly better while the edge was about the same. I based this on the examination of the Raw file. The posted JPEGs appear to be a little different. Probably due to the compression. </p>

<blockquote>

<p>There is some apparent light fall off on the corners.</p>

</blockquote>

<p>I didn't attempt to equalize the light levels on the two shots. Any light fall off you see in the corners is due to uneven light levels in the room. According to dpreview the light fall off they measured is about 1 stop (much better than the Canon 50 1.4 and 1.8). I haven't noticed any significant light fall of in the pictures I have seen. </p>

<p>Additionally I know from taking pictures of the night sky that the stars at F2 are sharper in the corners than photos taken at F1.4. This is not evident in the test chart pictures I have taken. In my opinion when comparing lenses you should do a controlled test as well as field tests. </p>

<p>One other note, I tried using my Keno extension tubes on this lens and the 20mm tube allows you to get an image on the sensor about half of life size. The 35mm tube got close to 1 to 1 macro but the working distance was so narrow that it probably isn't usable and the camera wouldn't auto focus. Not sure why.</p>

<p>Sigma 50mm at 1.4 using auto focus</p><div></div>

<p>Sigma 50mm F1.4 corner with auto focus.</p>

<p>Lets try that last one again...</p><div></div>

<p>Steven, did you take just one shot using AF or you took several?</p>

<p>If you took several, can you post a small crop side by side of all the shots to see the variance?</p>

<p>Same results here from a test on the 40D autofocus with the Canon 50mm 1.4 (center crop).<br>

The 40D was framed on an are almost 3 times smaller than the area the Minoltas were framed.<br>

These are three consecutive shots (individually focused with AF).</p>

<p> </p><div></div>

<p>The variability of the AF is obviously very large.</p>

<p>Detail wise, and using best pick shot on the 40D:</p>

<p>comparing the lines per pph on the 40D and on the Milnolta shots with TMAX on the light table; the 40D+50mm1.4 captures aprox 6MP of data and the Minoltas 35mmfilm+50mm lens with TMAX captures aprox 44MP.</p>

<p>The consistency on the results with the Minolta manual focus was perfect. No need to pick best shot there.</p>