Saturday, 7 December 2013

Sigma 30mm f2.8 EX DN review and thoughts

Ok, up front I'm a geek, but I'm a geek who's a photographer. So this isn't a typical review, if you want one of them you'll find plenty of sales blurb reviews out there.

For the impatient:
  • its a great lens for the money
  • image quality is good
  • if you are into legacy lenses then it may not be a useful buy
  • comparing to legacy lenses its makes me wonder why?
  • I might have an explanation for the DXO rating
  • I reckon this lens sucks battery due to its AF system (and conversely why I get lunatic long battery life out of legacy lenses on my GH and GF camera)
bottom line: the DMW-GWC1 is r.r.p of nearly the same as this lens, and that is just an attachment wide angle converter. So what I'm saying is you won't find much available new that's this price.

what I want it for

As it happens back in time when I used a 35mm film camera for my general photography, my favorite travel combo was a 24mm and a 50mm (with perhaps a 75-300 zoom if I was allowing myself more). So with the 14mm under my wing (and the x0.79 adapter) a 30mm would give me almost the same in my micro4/3 outfit as the 24 and the 50 did.

So, lets have a look at them, below is the Sigma 30mm beside the 14mm pancake and the 14-45 zoom

The astute observer will soon see that the 14mm prime is one end of the zoom range and the 30mm sort of close to the middle. The obvious question is that as I have the zoom why bother?

Basically its because:
  1.  the shallow depth of field rendering is there if I want it
  2. I like things more compact if I can
So it makes a difference which camera I use it all on if its to make any difference. I mean if I use the GH1 then the extra size of the 14-45 sort of vanishes. So basically this lens makes more sense on my GF1 (or your GFx or GX or other smaller Olympus pen) than on my GH1 or a Olympus OM-D

Now, just pause for a moment and think about that.

In my view the ultracompact side of micro4/3 is about quickly whip it out, use it and move on - while the OM-D GHx series cameras is more about photography where the photographer engages more seriously and more closely with the subject.

Knowing that makes a difference as to how you think about this lens and what the significance of my following points are. If you're a whip it out fast user then the answer is simple. Stop reading and go grab the 30mm, especially if you have the 14mm f2.5 ... its a great combo.

One of the first things that struck me when I opened the box and looked at the lens was how small the front element was, especially with respect to the OM 28mm I'd been using (you didn't seriously think I'd been without a 50mm equivalent all this time did you?)

Actually if you take another moment to look at that picture you can see that the newer lens coatings really make a difference to lens flare (something which my 28mm is better controlled than my 21mm, but that's another story).

Of course the lens element size is easily explained by the fact that the OM lens is designed to cover the 35mm area and the Sigma lens is only designed to cover 4/3 (and APS).

But it raises an interesting point, why is it so much bigger when something so much smaller can do? Like this is my Pentax 110 system 24mm f2.8 lens beside the Sigma.

I mean seriously if the 14mm can be as it is and have AF mechanism and an aperture, and this 1979 24mm lens is smaller than the 14mm, why is the Sigma this big?

The next thing I noticed was how much larger the Sigma's rear element was:

substantially larger than the element on the OM lens and way bigger than the rear element on the Pentax 110 lens.

The only thing I can attribute it to is that one needs to keep the light hitting the sensor as parallel as possible (a problem full frame digital Leica owners know about) as sensors (unlike film) do not like light arriving at off angles (and thus going through layers of glass at an angle ... if you don't get this go look at an aquarium close and look left and right ... distortions?). See this post for a little more detail.

For instance this is the OM28mm beside the Sigma 30mm

The lens cap on the OM lens is thicker than that of the Sigma and even then its shorter. So looking at the base plate you can see the Sigma is not "compact" (and wasn't the promise of micro 4/3 to have compact stuff?? Oh sorry ... banging on about this again ... its like I feel lied to).

However when you use the OM, because it was designed to work on a 35mm OM1 camera with a reflex mirror flopping around in there, it needs an adapter to 'space it off' the right distance.

So with the adapter on the OM lens and the lens caps off we can see that the 'whole thing' in legacy OM mount is actually bigger than the Sigma is.

So this seems like a good time to mention "SLRalike" bodies vs "compact" bodies. For on the GH1 using the OM lens feels quite natural but on the GF "compact body" the Sigma is much nicer. As the Sigma has AF that is also a real benefit there too.

Lens performance

I naturally took a series of shots at f2.8 f5.6 and f8 with both lenses confirming the already known (the lens vignettes as DXO have also reported) and curiously found something else.

When I do focus tests I tend to use manual focus and the "magnification assist" feature. When one manually focuses the Sigma lens one can hear the stepper motor moving the element in a series of "ticks" when the lens is moving in small steps (you can hear it too when its in AF right about when it snaps into focus inthe AF cycle.

What I found was that Sigma was often unable to focus exactly where I wanted to focus on, it would be a step either side of perfect. I would suggest that this has implications for why the newer Sigma 30mm seems may not perform as well on DXO testing. Now to be sure the differences are slight, but when you're suggesting that a lens / camera combo is 8P-Mpix vs 9P-Mpix you are talking slight.

So, lets look at 100% crops of the exact area I carefully focused on at f2.8 ... First the 100% crop from the Sigma

Then the 100% crop from the OM lens

You'll need to right click and open in new tab (or center click) to view these at the 100%.

Now the OM lens has a slight colour cast issue just on the edge of focus when its at f2.8, but this clears up when stopped down. The Sigma did not exhibit this.

Perhaps you can see that the Sigma focus is not exactly where I wanted it, on the chain. I could get it in steps either side, but I just could not get it right there.

Will this effect picture taking? No it won't ... I'm mentioning it because I believe that it may be a factor in effecting the DXO rating of the lens, for it they can't focus it perfectly (on a flat printed test sheet it will score lower.

How often do you photograph test targets?

The Sigma does vignette a little more than the OM lens.

Shallow normal

I happen to like the shallow DoF rendering in normal focal lengths (well and wide too) compared to the Kit 14-45mm zoom you just won't get shots like this

The background would be much sharper and the trees would be lost amid the background. Now personally I'd like even better separation than this, but in my view that can only realistically be had with larger formats. So the so called Full Frame (which ironically is only the full 35mm frame which was once regarded as miniature) is the only way to get this. In theory a f1.4 30mm lens would do it, but
  1. I've never seen a f1.4 lens in micro 4/3 between 24mm and 35mm focal length
  2. the 20mm f1.7 is close, but as its a bit wider then you need to work closer or you'll loose the effect.
  3. f1.4 still isn't quite as shallow as f1.8 is on a 35mm because the 2 fstop guidelines for determining the effective DoF of the micro 4/3 vs full fame is only really a guideline (see posts here, here, and here)


Basically I like the Sigma a lot. If I was using only a ultracompact body (like say one of the EP series) I'd definately have it and the Panasonic 14mm. It would be a great combo. It really helps cameras like GF1 attain the 'compact' dimensions and become convenient and powerful tools.

However for anyone using the SLRalike bodies who also happen to have some legacy lenses, the case for ownership becomes less compelling. Then the things which stand out are:
  • AF
  • flash compatibility (I don't have any native flash)
  • focus by wire more immediately (although bringing up focus assist is usually quick)
  • better colour balance (with JPG) and exposure decisions (compared to legacy lenses)

I paid €124 for my lens, but as you may know its now discontinued and the newer model is selling for €199, to me that's enough to change the equation. Lets look at some money figures:

A 28mm lens such as an OM or FD or Pentax screw mount lens will cost you about 60 bucks, less if you buy a non branded lens like a Tamron / Tokina / Vivitar .. probably 30 bucks. A reasonable quality legacy adapter will cost you anywhere between 30 and 60 bucks.

So if you have no other legacy lenses and no interest in fiddling in this area then there is no benefit to the older glass, so just grab the Sigma 30mm f2.8, it's your cheapest way to get a prime fast 'normal'.

However if you perhaps wanted to add some other lenses (like say a 50mm and a 100mm for some mid telephoto work) then you can share that adapter across the other lenses. If you are interested in that path then it would be something like this:
  • 30 bucks for the adapter
  • 30 bucks for a 28mm f2.8
  • 30 bucks for a 50mm f1.8 (seriously, don't get a 1.4 you'll be disappointed with the softness and weight)
  • 90 bucks for a good quality branded 100mm or less for a non-camera branded one
So for about 180 bucks (about the same price as just the Sigma 30mm) you'll get three lenses and add heaps more creative potential to what you may do.

So it all depends on what floats your photographic boat.

I may just end up selling the Sigma.

PS: I did sell it as the DoF differences compared to my 14-45 were in 99.9% of cases un-identifiable.

No comments: