clarity in digital (a retrospective with new data)

Well this is here because I became interested in the Sigma 30mm f2.8 lens. Before buying it I thought I'd do a little reading about it. So ... that's why this post started.

*Bigger is Better *More is Less *Less is More

Seems like an Orwellian double-think paradox.

For nearly 15 yrars I've been banging on about digitial cameras and film cameras. Being an IT specialist there is a great appeal to digital for me, but with 30 years of using film there was much experience and a high bar for digital to attain.

I have owned, tested and examined many photographic systems. The reason "why" was always to understand the tools and know what their limits were so I could make the best choices for my needs (which includes my budget).

The image to the left was taken using my 35mm outfit on Kodak slide film many years ago. My interests in digital lay in, convenience, speed of access, lowered costs. Since my first digital camera (in 2000) things have improved in iterations, going from .7Megapixels to my current camera being 12Megapixels.

When I bought my Panasonic G1 (12Megapixels) I owned Canon EOS digital gear (as well as film gear) and was getting tired of lugging the EOS digitals around (10D and 20D). I really appreciated many of the features of the G1 (excellent EVF and all that this brings to the table, tilt and swivel much bigger rear screen, much lighter). After some extensive testing I sold the EOS gear and have only kept the 35mm film cameras because they are just not worth anything to sell and as it happens have been useful photographing a wedding.

That was back in March 2009 and after spending time in the analysis I reached a few conclusions.

• bigger format was better for wide and normal
• bigger format was better for contrast and clarity
• smaller format made better use of telephoto lenses

While looking for clarity and resolution in my images I used tools like Norman Korens lens testing ideas and charts. These enabled me to see effective resolutions on both my Film and Digital camera systems.

Systems is the key word here ... but I'll get to that in a moment.

Looking at the data it supported what I was seeing in my images and that was that my G1 was a better system for clarity and resolution than my EOS system was. When applied to my 6x9 roll film and 4x5 sheet film systems I could 'see' the numbers showing me that they not only resolved more (despite lenses having lower lp/mm) but also had better contrast and texture.

When it comes to capture "Bigger is Better"

Back when I first had my 20D I was disappointed with the images from it (while all the while people were going ape over it) because they just weren't clear enough with EF-S lenses and my EF lenses just didn't look and feel the same on it. My 24 was no longer a wide and my 50 no longer a normal.

Somehow these lenses simply looked better on full frame.

Owning the G1 seemed to be unilaterally better than the 20D (EVF for critical focus, shorter flange distance opened up wide choices of cheap creative alternative lenses, actual resolution was higher, slightly smaller sensor gave a more convenient x2 rather than x1.6 factor...) and somehow also made it clearer to me that Full Frame had something that neither APS nor 4/3 did (plenty of posts on that here).

Quantitative data

Fast forward to last night and I was looking up data from a lens testing site about a Sigma lens I'm interested in. I learned that since I was doing much of my testing (2009) a group has developed a very convenient lens testing metric - the Perceptual Megapixel (announced in 2012).

This is very useful metric, perhaps the most useful metric I've ever seen with relation to digital imaging. For it brings together the entire system (as did the Norman Koren method) yet gives a single number which can be applied in parts of the analysis of lens on almost any camera. Why is it useful? Well previously the only 'metric' on lenses was stuff like LP/MM measurements (quite subjective) and MTF curves (for full on experts), as the guys over at DXO say:

Can you define MTF? Do you know if an MTF20% of 50 lp/mm is better or worse than an MTF 50% of 30 lp/mm? And when reviewing an MTF chart, can you distinguish which curve is best? The short answer is probably no.

Since I bought my G1 (and swapped it later for a GH1 to get video and then added a GF1 last year) I have seen nothing compelling to encourage me to "upgrade" my micro4/3 cameras to any newer model. Seeing this data now gives me some metric to fall back on to support what I was seeing (but it seemed that few if any others were seeing NB:

cameras were getting more megapixels but the images just seemed to have the same levels of detail.

To wit lets look at a few lenses from the dxo site. As I was interested in the Sigma 30mm f2.8 I found that review first (and from there the P-Mpixel):

So the Sigma has 8 Perceptual Megapixels, the 'illustrious' (and slightly expensive @US$529) Panasonic Leica 25mm f1.4 gives you only 10Mp (from my 12MP camera) and the oft dribbled about on forums Oly 45mm (@US$400) gives you 9Mp. Hmmm ....

So, looking at a few more of the 'top micro4/3 lenses you simply have to have' we see:

9, 9 and 6P-Mpix. Seeing that rating on the 12mm f2 makes me even more comfortable that my bang for buck (based on what I saw in images) x0.79 adapter was good enough.

I get sick of the dribble I hear about how good the original Olympus 17mm f2.8 was (and how it was sooo much better than the zoom, and don't even start me on the 'stellar' 20mm) seing this low rating only confirms what I saw with my eyes. Well to my eyes it wasn't great and now there is data to back this up.

So looking at the performances its not ball tearing stuff is it. I mean none of these lenses will warrant a move up to 16Megapixels in your camera ... you'll just get more mush. In fact it shows that none of these "super zooms" even give you much more value than the original kit 14-45 zoom that came with my G1. It puts some metrics behind the arguments made by people that the Olympus micro4/3 anything zoom on the OM-D anything will compete with Full Frame ... it just can't and this new understandable data metric seems to support what you see when you look carefully at the DPreview comparison images.

So Less is More (more money back in my pocket).

In comparison to Full Frame some quite humble lenses (and my EF24 f2.8 is always bagged by people from the Kingdom of Wang) as well as one EF-S zoom

So no matter how many MP your camera has (and the 7D has an 18Megapixel APS sensor) if you use that lens you'll get effectively no better than 7Mpix (or about what I get on my micro 4/3) while if I used the older original 5D I'd get the full 13Mpix that the sensor had with either my EF24 f2.8 or my EF50 f1.8.

Worth noting is that the EF24 f2.8 when tested on an APS camera gave no more than 7P-Mpix (due to higher magnification demands of the smaller sensor)

This has helped explain to me what I was seeing when 35mm images taken with my EF50mm f1.8 were sharper and clearer than what I ever got with any of my smaller sensor digital cameras.So as well as better shallow normal I also actually get higher definition too.

The older EF24 f2.8 is not available new anymore, but as a used lens in excellent condition you'll find them for less than US$300, which is much better bang for buck than the Olympus 12mm f2.0 at US$800 and will give you higher resolution to boot!!


These numbers make it clear that if I actually want higher resolution and better contrast I'll need full frame (cos APS and micro4/3 just don't have the numbers). This re-enforces that with the lenses being as they are there is no point in having a compact camera more than of 12Megapixels.


So again Bigger is Better, and Less is More.

Does this mean I am disappointed with my micro4/3 move?
No, because it still gives me a light weight camera to mount many and varied lenses on.

My initial choices for moving from my 20D to the G1 was to have a high quality lightweight camera system that was flexible. My GH1 and GF1 are still exactly that. I now know that do get better performance from my micro4/3 system than I did from my APS system as well as better options for low price and creative lens options.

To me pictures have never been about Megapixels and you'll find in my writings for many years that I've often felt that a good and sharp 6Mpix was enough for most needs. So now with this DXO metric I'll say that a 6P-Mpix is good enough :-)

I'll leave you with an image which is an old favorite of mine, it was taken with the EF24mm f2.8 on film. Its certainly got way less than 8P-Mpix in it, but due to the nature of the way things works prints nicely up to 70cm. Please click on it for a larger view

but I like it not because its sharp but because it has feeling. Its an nice photo of my friend and excited dogs down on the beach on a nice day. Knowing how digital blows out in the highlights, I know that I'd have never been able to get this image with a digital, so I'm glad I had only this antiquated equipment.

summary

So I'm really glad that there is now a metric to help me to make appraisials faster. I know that my micro4/3 has limits and I'm willing to live with them. Understanding the limits makes it clearer to me why I won't benefit in the upgrade. In fact something I have not touched on here is I will benefit by not upgrading because more megapixels in the files just means more storage. More storage costs, longer backup times, bigger SD cards .. and all for nothing that can really be seen in the images.

So I'm going to buy the Sigma and I reckon that it'll be a nice addition to my GF1's compactness (cos that 14-45 zoom is a bit bulky). This will give me a nice lightweight travel and snapshot camera

GF1 (380g) + 14mm (55g) + GWC1 x0.79 wide adapter (70g) + Sigma 30mm (135g).

It'll weigh 250g less than just a 7D or a 5D body and give me effectively a 21mm f2.5, a 28mm f2.5 and a 60mm f2.8 Sure it wont have the Megapixel count but who can see that? The camera only has one eye, but those who only read data and chase the megapixel madness are just as blind as King Wang

A wonderful quote on the DXO site:

The Perceptual MPix measure confirms certain rules of thumb such as a 12 MPix full-format camera is sharper than an 18 MPix APS

Just say More Megapixels and the followers of King Wang chant:

Long live the King!
King Wang King Wang King Wang King Wang

but to me Megapixel madness is
King Wang King Wang King Wang King Wang King Wang King

Portrait lenses: 5D vs GH1

One of my favourite words is fungible. I'd never heard of it till I worked in the Finance industry (and who'd have thought but its a finance namespace word). Its defined over at Wikitionary as:

Adjective

fungible (comparative more fungible, superlative most fungible)

1. (finance and commerce) Able to be substituted for something of equal value or utility; interchangeable, exchangeable.

With that definition in mind, the purpose of todays post is to explore the fungiblity of 50mm on 4/3 vs 100mm on full frame.

background

When digital SLR cameras came out I was unimpressed by the APS size sensor. I felt that it twisted lenses into something I was not used to. My fine 24mm wide angle became a middle or nothing semi-normal and my favourite normal (EF50) became some sort of half assed tele (something like 80mm which is too short IMHO). I ended up needing to buy alternative zoom lenses to cover the angles I liked and the DoF was never what I wanted.

Then I tried 4/3 and found that the x2 factor on the lenses was much more acceptable to me than the x1.6 of APS. I did find that the optical SLR viewfinder was pathetically small and so it wasn't till micro4/3 came out with the electronic viewfinders that I was fully comfortable with focus (and yes, I had a number of focus problems with APS cameras which included backfocus and front focus issues as well as inability to clearly manual focus on the small focusing screens).

Since I started using micro4/3 cameras one of the questions I have sought answers to is the ability to substitute half the focal length at 2 stops brighter and get the same thing. Back in March 2010 I made a comparison of this however I used 35mm negative, which didn't fully satisfy my interests because I still wonder about the utility of a 5D in what I photograph.

As I recently borrowed a 5D (for testing the Olympus 21mm f3.5 wide) I thought I'd do another test to satisfy my curiosity (and of course provide information for others pondering the same thing).

Too many reviews compare things with no context other than the optical one. I think that's invalid because I don't know anyone who just buys based on what the magazines say. Most people need reach into their pocket and pull out some money. So in someways there needs to be an examination of cost benefit. So lets examine some costs.

Both the GH1 and the 5D are only available now as used cameras (which to me is a good thing as they are cheaper this way, let someone else take a big depreciation hit if you can). A good used 5D body still fetches about $1000 while a good G1 about $250 and a GH1 (if you were after video as there is no other significant difference between the G1 and GH1) about $400.

The lenses uses in this test were the Canon FD 50 f1.4 and the Olympus OM100mm f2.8 - one can expect to pay about $100 for the FD50 1.4 and about $200 for the OM100mm f1.8 So one can take advantage of cheaper lenses. Because shorter lenses cost less than longer ones of equal quality and also 50mm was once a really popular focal length.

Then there is size the 5D is about twice the dimensions of the G1

So not only do you pay twice as much for the 5D as you do the G1, you have to carry around twice as much of a monster.

People often discount this fact when making considerations and instead ruminate about "what makes the ultimate image".

This "ultimate image" nonsence forgets an important fact in photogaphy: if you don't have your camera with you then you can't take pictures with it.

Hmmm?

This is of course why I bought a G1 and sold most of my EOS gear back in 2009 (after much rumination and after buying the G1 and having if for some months just to be sure).

Clearly then this test is not without me having some pre-conceptions from the outset. I think its important to say that some of my preconceptions were upheld here, while others were challenged and I think its fair to say I learned something in here which I didn't expect to learn (but wondered about in another context)

examination

In this test wanted to examine how well the micro4/3 camera would hold up against a full frame camera in respect to portrait focal lengths. I chose 100mm for the focal length because I've always like it more than 135mm. Canon and Nikon and Olympus alike have all made good sharp f2.8 100mm lenses for some decades. I happen to own a Olympus OM100mm f2.8 which I think is one of the sharpest lenses ever made (the TS-E90mm would get my vote as the best) and the 135mm range is a bit patchy if you ask me. Likewise there are plenty of good 50mm lenses out there (I own a few of them) which of course makes the basis for this comparison.

So to compare a 50mm lens on micro4/3 to a 100mm on a full frame one needs to consider that to get the same DoF look and feel, you need to keep the aperture 2 stops brighter on the 4/3 camera. So in theory 50mm @ f1.4 <=> 100mm @ f2.8. But of course its not without problems because (among other things) the aspect ratio is different the 4/3 format is far more square looking than the 3/2 format of full frame.

Notice that when covering the same width that the 4/3 gives that bit more along the top and bottom.

Next I'll state that all images were taken

• in RAW
• on a tripod that didn't move
• converted using ACR 5.6 with exactly the same parameters
• exposure set by my Gossen light meter and manual setting applied to the cameras

This was done so as to get the images as close as possible in terms of processing (camera JPG's would be more difficult for the nature of this comparison)

Something which came out right away was that: if you are taking shots in full sunlight that using f1.4 is a challenge.

The shutter speed required is often exceeding what your cameras shutter will allow. For instance on a sunny 16 kind of day (like this was) I was using 4000th of a second to get f1.4 and even then was needing to have shadows as part of the picture or have a washout. Check the nuclear glow of the shirt back for instance. At 4000th of a second fill flash is out of the question too.

So it seems that fast lenses and daylight are not good friends.

So anyway now lets take a look at the images.

First the image from the Olympus 100mm at 2.8


and then the 4/3 camera with the 50mm at 1.4
The first thing I notice is that the colour and contrast is different (there is also bokeh but that's for another post). The FD 50 when opened up to 1.4 is really soft and dull looking which influences the colour. This is clear in the 100% view below, especially where the stark contrast border between the white velcro of the cap strap borders the darkness of the hair in shadow. I would call this "blooming".


Don't get confused and think this 'flare' only exists where there is bright light, it exists all over the image area and is what serves to make the lens "low contrast".

If we now look at the OM100mm at f2.8 we see definitely better contrast.



Its interesting to note however that the outright resolution of detail between the two lenses is quite similar.

This is consistent with what pulled me away from my 10D and 20D cameras in favor of the Panasonic G1 ... it just has heaps of detail.

On that subject its a good time to observe that the 5D turns its 36x24mm capture area into 4368 x 2912 pixels while the G1 divides its (much smaller area) 18x13mm into 4000 x 3000. This means that while the outright capture of detail is quite similar the micro4/3 is actually a little more demanding of lens quality. Since the FD50 f1.4 (or in fact almost any super bright lens) has always been regarded as a little soft fully open, it translates to a bit more than that here.

So when you stop the FD50 down to f2.8 it clears up immensely

to be more or less equal to the contrast of the Olympus 100mm lens.

but of course loosing that nice shallow DoF. I encourage you to open up each of the above images in a separate tab to allow you to click between tabs and see the differences jump out.

Perhaps the new Olympus 45 f1.8 lens would solve these problems and yield a lens which would

• have the contrast I find in the Olympus 100 f2.8 on full frame,
• have at least similar (if not better) sharpness
• be more compact and light weight than the FD f1.4

The lens will set you back about $400 as it seems to be panning out, which is quite attractive. The initial discussion of the new Oly 45f1.8 indicated prices would be much higher, but if it does come in at $400 that will put it right on par with the typical 100mm f2 lens.




So you would then get the compact benefits of micro4/3 without needing to pay through the nose for smaller.

Back when micro4/3 came out there was of course no such lenses available, but the potential was there. So to actually see and explore this potential I have experimented with adapted 35mm lenses so that I can get actual experience with images, not just a theoretical idea of what I can expect.

Both lenses used in this test were designed for different cameras than the EOS series, and so need adaptors. The OM lens was made for a camera with a shorter flange distance than the EOS, but not by much. So it only has a slim adaptor. The FD being used on the micro4/3 however has a much longer adaptor because (again) the flange distance effects the design of the lens (has to clear that moving mirror).

Paradoxically the 50mm lens actually becomes bigger than the 100mm lens when both are on their respective adaptors.

Of course a 50mm lens does not need to have such a massive stand off on a camera without a mirror. In this photo I show the Pentax 50mm lens (far right) beside the 50mm OM lens (on adaptor).




So the new micro4/3 Olympus 45mm f1.8 is likely to be about the same size as that little pentax lens. If you happen to be interested in more compact 50mm portrait lens than the FD 50mm f1.4 I suggest you consider the little Pentax. I have reviews on them here , here and (perhaps the most interesting) here.

Of course adapted lenses lose "niceties" such as Autofocus, Face Recogntion Autofocus, auto aperture and a few other things which can be important (for people who don't know how to focus a camera or set an aperture). Since that time lenses have begun to emerge which don't cost an arm and a leg, may give better image quality and provide all the creature comforts (crutches?) for the photographer who needs them. For what its worth adapted manual focus 35mm lenses cost about ¼ of what one would pay for a modern equivalent.

However there is more interesting information available in this comparison yet. While the depth of field may be reasonably equal in a gross comparison there are some significant differences.

• The 100mm at f2.8 has a more shallow depth of field at the subject

With both images I tried to focus on the back edge of the cap. Using the magnify zoom focus assist on the GH1 it was easy to get that spot. Looking carefully its clear that the 50mm lens on the 4/3 the focus zone is much deeper even at f1.4. By the distance from the ear to the eyelashes, they are starting to go out of focus on the 100mm at f2.8 but not on the 50mm at f1.4. This means also that you won't get that on the Olympus 45 f1.8 either.

This (shallow DoF) is exactly what one wants in a classic portrait lens.

The ability to have focus sharp and defined on the eyes (my wife wanted to keep a little more privacy) but be soft by the ears or the back of the head, especially when the head is turned slightly.

Before people mention anything about pixel peeping, this sort of thing will become obvious on a 8x13 print and more so on a larger photo. Even if you don't "see it" obviously here it will be what makes it "feel better" when you examine prints.

This is not to say that the micro4/3 is bad by any stretch of the imagination. Indeed its pretty bloody good.

While playing around with these images I noticed something else, and that was the 5D also had a better dynamic range. You'll notice that the blacks in the shadows were better resolved? Thats because they had less 'noise' (as well as not being covered up by the flare)



The above are both taken at f2.8 (*where the FD lens became quite equal to the OM), the details in the shadow (arrows) are present on the 5D (right hand) while being muddy on the GH1. At the same time the highlight transition to washout (elipse) was similar. See the differences in the hair clarity in the shadows? If you were trying to dig a little into the image to pull out more shadow detail then the micro4/3 would give you a little less clear shadow detail than you'd get out of the 5D.

Lastly I thought I'd present the difference that one gets using a camera like the 5D in terms of outright printable size. The 5D image is slightly more pixels wide (4368 vs 4000), so if you were wanting to keep the aspect ratio at 3/2 then you'll get a slightly bigger print from the 5D, so printing at 300dpi from native:

• 14 inches wide at native pixels on the 5D
• 13 inches wide at native pixels on the GH1

Which is not exactly startling is it. On the plus side the 5D will tolerate more enlargement of pixels (upsizing) from native because it has a slightly better image quality (as identified above) and has a bit more to start with. In my comparisons above I've scaled the 5D back to the 4000 pixels of the GH1 so as to make it easier to compare. Here is the actual pixel comparison from these images.


So there is a minor increase in size of features in the picture, but personally I feel that if you wanted to print BIG or you want to capture every last skeric of detail then the 5D would do it that bit better.

Ultimately my call here is that the micro4/3 gives you 95% of the image feel and 99% of the image quality that a 5D will give. If the pursuit of that few percent advantage is worth doubling your money in buying a camera (and lenses)

PS: and now, after a long delay Part II is completed (sorry about the delays but some times life gets in the way)