Steve Spencer
Offline
Upload & Sell: On
|
 Re: Voigtlander 50mm f/3.5 APO-Lanthar Review | |
Ripolini wrote:
philip_pj wrote:
I perceive that it's clearly a better landscape lens....
The tests performed by @Fred Miranda@@ are quite interesting, and show rather impressive results.
However, looking at MTF plots published by Cosina, I would prefer the 50/2 AL as a landscape lens: at f/4 the 50/2 curves are higher than those at f/3.5 & f/5.6 of the 50/3.5 VM, and flatter, thus suggesting a more even rendition across the frame.
Probably to see the difference between these excellent lenses, a 60 Mpix sensor is necessary.
The difficulty in comparing these MTFs is we don't have the two lenses at the same aperture for any of the charts, and what we have mostly suggests very similar performance which is what we see in Fred's real life tests. Let's start by speculating what you would get at f/5.6. The f/2 lenses has an MTF40 with 82% contrast in the center for both sag and tan at f/4. It will drop a bit at f/5.6 let's say 80% contrast for both sag and tan. The f/3.5 lens has 78% contrast for both sag and tan at f/5.6. That very small difference I don't think is going to be seen even with a 100 MP sensor (because then we will get more diffraction).
Let's move to the mid zone and let's compare at 12.5mm from the centre. The f/2 has an MTF40 with 81% contrast for sag and 72% for tang. It will again drop a bit at f/5.6 let's say 78% for sag and 70% for tang. The f/3.5 lens has 70% contrast for sag and 61% for tang at f/5.6. Is that enough to see a difference? Maybe on a 60MP sensor, but again will diffraction hide any difference you might see. I am sceptical it will make a real world difference.
Now let's move to the corners and let's compare at 20mm from the centre. The f/2 lens has an MTF with 78% contrast for sag and 76% tang. It will again drop a bit at f/5.6 let's say 76% for sag an 74% for tang. The f/3.5 lens has 65% contrast for sag and 63% for tang. Again you might see that on a 60MP sensor, but you might not.
Those are some pretty small differences in MTF. Just because you can see them on the chart doesn't mean you will be able to see them in photographs. What we know is that you won't see them on a 40MP sensor as Fred's tests have shown. We also know from lens rentals blog MTF tests of multiple copies of the same lens that these differences are well within the typical difference we see between copies of the same lens. So, sure the MTF might be a little higher on average for the f/2 lens, but getting a top performing copy of either lens is probably more important than which lens you get given these small differences in MTF. I remain skeptical that you will see actual difference between the lenses at f/5.6 with a 60MP lenses (especially given that diffraction will start to show on a 60MP lens at f/5.6 if you magnify to the pixel level). I think the bigger story here is how similar both these fine lenses are and especially so stopped down to f/5.6.
|
