p.5 #1 · “Full Frame Equivalence” and Why It Doesn’t Matter
Jman13 wrote:
For the 45, to get the same FOV and same blur/DOF as on full frame you'd need a 42.5mm f/0.9. Voigtlander has announced a 42.5/0.95 that will get you darn close, and Panasonic will have a 43/1.2 out later this year that isn't that far off.
The 50mm question is similar...the 25/0.95 will be essentially identical to a 50/1.8 in terms of DOF.
How would those lenses compare in terms of size and weight? Just to extend the "equivalence" discussion a little further.
p.5 #2 · “Full Frame Equivalence” and Why It Doesn’t Matter
The lens equivalence makes only sense when we are using the same lens on 2 different formats, say a 24x36 lens on APS-C body, or a 6x7 lens on MF, and adapted to 24x36 or APS-C bodies.
The rest is semantics imho. Each system has different dedicated lenses. A standard lens for 6x7 can be 90mm, 100mm or 105mm, or for 24x36, can be 40mm, 50mm, 58mm, or even 60mm.
When I shot multiple formats on film many years ago, I honestly never wasted my time in doing lens conversions. I had a lens line up for each format, typically standard, moderate wide, ultra-wide, and moderate telephoto, and selected the most appropriate FL for the subject. I couldn't care less if my 50mm for 6x7 was equivalent to 22.5mm or 24mm in 24x36.
p.5 #3 · “Full Frame Equivalence” and Why It Doesn’t Matter
Access wrote:
I have a question on this whole 'equivelence' thing.
From experience I can tell a µ4/3 camera with the CV 25/0.95 is no match for a FF camera with a 50/1.4. (This is subjective of course.) You get better, as in very much smoother, bokeh with the FF setup. This is from the Sigma 50/1.4 EX and the old Canon EF 50/1.4.
The DoF and the transition zones are pretty much the same, as predicted by theory, for the setups at 25/0.95 wide open and the FF set to f/2.
The first few samples from the CV 42.5/0.95 aren't impressive; the motif was stupid (a close-up of a camera) and didn't tell us much but the background OOF highlights were comet-like and with bright outlines. We need more samples before knowing.
p.5 #4 · “Full Frame Equivalence” and Why It Doesn’t Matter
15Bit wrote:
How would those lenses compare in terms of size and weight? Just to extend the "equivalence" discussion a little further.
The CV 42.5 will be heavier, but it's a sold brass and aluminum construction. All the voigtlander lenses are pretty chunky. The Panny 43/1.2 looks smaller than an 85/1.8 and will likely be a little lighter too. The size and weight advantage isn't there if you are trying to match DOF. If really shallow DOF is your thing, FF is what you want. It is nice that these options exist, though, especially if you only want that real capability at one focal length or so...the rest of the kit can be kept small, and you can get the one lens to give you that sliver thin DOF. For instance, I may eventually get a CV 17.5 f/0.95. I really loved that lens when I tested it...surprisingly good at f/0.95 and the ultra wide aperture allowed me to shoot at night at base ISO. (This is at f/1.2 a and ISO 200)
p.5 #5 · “Full Frame Equivalence” and Why It Doesn’t Matter
Access wrote:
(I've learned not to trust the DOF calculators online because most don't take into account the real effects of background magnification).
I believe that most tables are built on the Thin-Lens Approximation, which can deviate significantly from real lens designs:
p.5 #8 · “Full Frame Equivalence” and Why It Doesn’t Matter
Access wrote:
If I have a lens, like let's take the Canon 85mm f/1.8 used on a 5d ('full frame' camera). It's used for portraits all the time, so often narrow DOF and pleasing 'bokeh' matters.
Now if there were to be a micro four thirds lens made, to match the same size and bulk and field of view of this lens, ie. a 42.5mm f/??, would it match the photos taken with the 85mm/FF setup in terms of DOF and 'bokeh'?
No, unfortunately not. One must understand that the possibility for correcting aberrations is lesser, the larger the relative aperture is. So, if the entrance pupil is the same on both the 85 and 42.5 mm lenses, the 85 is most likely much, much sharper per image height (at least wide open) and will have a different look, including bokeh. Now, of course bokeh is a matter of taste and for portraits you might even prefer the softer look expected from the shorter lens.
A slower but longer lens is most likely better corrected for spherical aberration, which I believe is the most significant reason for these differences. This means that you can get more "pop" at the same background blur, with a steeper falloff from sharp to unsharp.
Here's an example with the Pentax 105/2.4 wide open on the 6x7 medium format which is equivalent to ~50/1.2 on FF and 25/0.6 on MFT. I'm sure most of you know that you would not get nearly this high local contrast with a smaller format at the same AOV and DOF.
p.5 #9 · “Full Frame Equivalence” and Why It Doesn’t Matter
Makten wrote:
Here's an example with the Pentax 105/2.4 wide open on the 6x7 medium format which is equivalent to ~50/1.2 on FF and 25/0.6 on MFT. I'm sure most of you know that you would not get nearly this high local contrast with a smaller format at the same AOV and DOF.
How large is the 105/2.4 6x7 medium format lens though? I don't have one but I've seen a few canon 50mm f/1.2 lenses in actual use; they didn't seem like that large of a lens.
p.5 #10 · “Full Frame Equivalence” and Why It Doesn’t Matter
Access wrote:
How large is the 105/2.4 6x7 medium format lens though? I don't have one but I've seen a few canon 50mm f/1.2 lenses in actual use; they didn't seem like that large of a lens.
I haven't got much to compare with, but I'd say it's about as large as a Canon EF 50/1.2, but of course much more solid and heavy since it's manual focus. And the distance to the film is A LOT larger, so the total combo is huge even if the camera would be smallish (which it certainly ain't).
And, I think this illustrates the problem with equivalence. You just can't make a shorter lens with the same entrance pupil that gives the same performance on a smaller format.
p.5 #12 · “Full Frame Equivalence” and Why It Doesn’t Matter
Technical semantics aside, the "look" is just different between formats. I use to know a pair of identical twins, they look identical by any measure, but for some reason, after knowing them for some time, I instantly was able to recognize who was who. I don't know what it is about formats, but the same sort of logic applies, there are some small differences in larger formats that go beyond angles and DOF that aren't replicated in the smaller formats and the "look" isn't there. Not to say that it is bad, but just different.
Not really a big difference, and some of this is simply because the Pentax has a much larger mount.
Medium format lenses can have hilariously lopsided barrel:optics ratios; look at a Mamiya 80/4 for an example of tiny optical cells in a gargantuan mount
Typical fashions in mounting barrel aside, there is likely to be little size/weight gain moving from lenses for bigger formats to "equivalent" smaller ones, as this Pentax/Canon example demonstrates. "Equivalent" lenses need equal entrance pupils, so roughly the same diameter of glass --- and more/thicker elements in the smaller format version to achieve similar aberration correction at lower f-stops. Other than overall length, lens scaling is actually unfavorable for smaller formats in weight/cost/complexity.
These all have nearly the same entrance pupil. The two on the left are "equal", but already in this image you can see that the Nikkor has a more extreme design because it's half the focal length. The 105/2.5 could probably cover 6x4.5 with some vignetting and is still really small due to a narrow barrel and mount.
Edit: The Pentax has also a very much more distant exit pupil than both the Nikkors (which are about the same). So I bet it could have been smaller with a shorter flange-to-film distance.
p.5 #15 · “Full Frame Equivalence” and Why It Doesn’t Matter
But in a lot of cases, like in the case of 50mm f/1.8 (FF) vs. 25mm f/0.95, the smaller format lens is (overall) skinnier, but longer; the medium format lens (overall) fatter, but shorter.
2.7 x 1.6 inches for a 50mm f/1.8
The _considerably_ more expensive 25mm f/0.95 being 2.3 x 2.8
Basic volume might be similar at least.
Honestly I haven't done a lot of comparison between the systems in terms of images (because I almost never have both on me at the same time). I only use the micro four thirds system if the day calls for it. I can sometimes do pleasing portraiture with the micro four thirds, but it requires more special attention to a number of factors compared to the full frame.
In one way the argument makes little practical sense because in general, a u4/3 user isn't going to want a lens that is that large. Especially when it comes to the size of some of the zooms. And a lot of the most useful lenses from the format are pancake lenses which canon only started to experiment with (40mm f/2.8 for instance).
p.5 #16 · “Full Frame Equivalence” and Why It Doesn’t Matter
I did a rough comparison between the Hasselblad 80/2.8 on 6x6 and the Voigtländer 35/1.2 on NEX, which are nearly equivalent except for the aspect ratio.
p.5 #19 · “Full Frame Equivalence” and Why It Doesn’t Matter
Makten wrote:
I did a rough comparison between the Hasselblad 80/2.8 on 6x6 and the Voigtländer 35/1.2 on NEX, which are nearly equivalent except for the aspect ratio.
NEX:
...
HBL:
...
Now crops...
...
So much for equivalence. Both were shot wide open.
Nice example. I would have expected less DOF from the 80 at F2.8 on 6x6, but there you go.
p.5 #20 · “Full Frame Equivalence” and Why It Doesn’t Matter
Not serious about the "trick"
Most comparisons are made with the focus point in the center though, missing the important sharpness across the frame. This one was actually quite realistic.
