Is my thinking about equivalence right?

Started 3 months ago | Questions thread
OP Muster Mark Contributing Member • Posts: 588
Re: No, not really ...

jwilliams wrote:

Muster Mark wrote:

Hi all, I realize this is NOT the topic everyone loves to discuss and I totally understand. I hope no-one feels annoyed by this post. That said, after some investigation I have come to the conclusion that "traditional" equivalence math is only useful as a rough heuristic to get a sense of what DOF will be and NOT a reasonable way to compare individual lenses or judge cost/performance of lenses in different systems.

No, not really. Equivalence is more than DOF or even mainly about DOF. I'll not go into any long winded discussion, but here's an article on this site that is a good read on the subject.

Equivalence is useful if you have any interest in light (and as a photographer, you probably should): Digital Photography Review (

I've actually read this and many other articles. They assume ideal lenses when making total light calculation. Is this a huge deal? probably not, but it should be noted.

Most m43 lenses vignette badly also. This has less to do with format and more to do with current lens design where flaws like vignetting are tolerated more because they can be corrected in software. Just like distortion. All formats suffer from this.

Except not nearly as much. Just look at the data on

Comparing lenses holistically: When more is taken into account than just pupil diameter, it seems to me at least, m43 lenses are not overpriced. For example the 25mm1.2 is optically pretty amazing when it comes to corner to corner sharpness, longitudinal CA correction (which is hard to correct in post, if my understanding is correct) and bokeh quality (not size).

A lot of m43 lenses are overpriced (the f1.2 primes are good examples) compared to equivalent lenses in other formats and the 25 1.2 is actually a good example of this. In the next paragraph you talk abut the Sony 50 2.5 which is equivalent to the 25 1.2 and from all I've seen and read will produce at least equal and probably better results for less money.

My point is that it is equivalent only in terms of bokeh ball size. the olympus gives much smoother bokeh so the images won't look the same. Also if one is shooting both wide open, the Sony vignetts more and is not sharp in the corners while the olympus is. I think a reasonable person could conclude that the sony offers better value for money, but they won't produce exactly the same images. This was really the crux of the point I was trying to make. To actually match an image created by the olypmus 25 @1.2 you need to stop down a lens for FF of similar or greater cost. Those lenses are bigger and offer the potential of wider equivalent aperture. So again, you could say they offer better value.

For half the price one could use the Sony 50mm 2.5. This amounts to being about half a stop dimmer due to vingetting, the bokeh while the same size is much busier. Longitudinal CA is only a smidge worse though. Oh and yeah if you want a sharp full frame you need to stop down to f4 (the 50mm 1.8 by sony is not really worth looking at if optical performance is something you care about).

Or if you shoot Canon you just use their 50 1.2 which is very sharp right from 1.2. You can't make wide ranging conclusions from just 1 lens from each format. Too easy to cherry pick and get the results one is aiming for.

I don't think I was cherry picking. I was just looking at two mounts. The canon looks like an excellent lens.

The Sony GM 50mm 1.2 lens performs very well when stopped down (and is pretty good wide open), but now we are back to being much heavier and costlier than the olympus. I am NOT saying it's a rip off, but I also don't think the lens needs defending as no one seems to doubt it.

Until one has shot with one of these FF 50 1.2s I really don't think they can appreciate these type of lenses. I've never been a huge ultra shallow DOF fan but I've got the Canon 50 1.2 and the capabilities of this lens are fantastic. Once you've shot one its hard to go back to something like an ordinary 50 1.8 much less something like a m43 25 of any aperture. I'm packing for a trip right now and despite being rather large and heavy that lens is going along because of its very unique capabilities.

Fair enough. I hope you have a great trip!

The Zeiss 55mm 1.8 has lovely bokeh, but bad Long. CA and needs to be stopped down to 2.8 to be sharp.

Sigma ART lenses start to really shine honestly. Generally very well corrected optically, much less vingetting on FF than other lenses when wide open, and even slightly cheaper priced to the olympus. They are significantly bigger though (the 50mm 1.4 is 815g, versus 410g for the oly).

So what do we make of all this? My take away is that there is no free lunch.

My favorite saying, but I'm not sure you've got it in the right context.

If you want a certain level of optical performance you're going to pay for it regardless of the size of the sensor sitting behind the lens. Take a bunch of m43 lenses and find their APSC and FF equivalents and you'll discover there is very little size/weight difference between the equivalent lenses from the different formats.

Sure. I think the point I was trying to make that you didn't pick up on is that they don't really make premium, small (dim) lenses for FF systems. To match the IQ aspects of a premium m43 lens you need to also be looking at premium lenses. The stuff that is equivalent in terms of max aperture also seems to have other flaws.  That's really all I was saying. Truly equivalent lenses (and by that I mean not just aperture size but all the other aspects of the lens too) don't really exist. And it seems to me that you generally get what you pay for on any system. Of course individually one might not value the optical aspects that one maker chooses to compromise to save money etc. so person to person there are better value options or worse options.

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