Feelings about the Sigma in Real Life

Steaphany

Since my first and introductory post was to the Why not women in the forum? thread, I felt that Tony's comments and questions regarding my SD14 experiences would be best served here:

rbelyell · Expire: 2014-01-31

thanks steaphany. agree with you on the negatives, plus no in body IS and a terrible viewfinder, both of which conspire to wreak havoc with mf lens use. really, for color photos, you cannot shoot above iso 400.

positives are a lovely, 3d film like effect for the photos; lovely color and lots of depth. if we go beyond the tech stats, which by the way are way over my head, i am wondering, for the same number of negatives, how the sd14 IQ would stack up against say a canon 1ds full frame; or erasing some of the negatives, how it would compare with even a pentax k20d. again, this is intuitive, but im thinking that both are going to yield higher quality images, one simply via more 'horsepower' and the other via compensating for the sd14s significant negatives.

what are your thoughts? mine are i wish i had the resources and talent to conduct the tests!

thanks again
tony

Steaphany · Posted: Fri Nov 20, 2009 4:03 am Post subject:

The lack of Image Stabilization is not an issue for me. When I started in photography with a Yashica Mat TLR, there was no image stabilization, but tripods did the job and are still capable today.

With my SD14, I have an RF remote that connects to the CR-21 jack. Being completely wireless, apart from any breeze or ground vibration, the SD14 is rock steady.

A point to remember is vibration suppression is all the more critical with long focal length lenses. The Hit and Miss engine photo was shot through my Orion 1,250mm Maksutov Cassegrain telescope which yields a 0.95� x 0.63� angle of view on the SD14. (equivalent to a 2,125mm lens on a 35mm camera) I had my SD14/Maksutov Cassegrain mounted on my astronomical mount/tripod and controlled the camera from the RF wireless remote with the SD14 in Mirror up mode. To capture the full engine required 9 over lapping frames which I stitched together in post. The image clarity was fine in the whole set.

I agree that the SD14 viewfinder is not the best design, my personal preference is a ground glass focusing screen, but I have not seen any SLR with a ground glass. I'm able to make due with the SD14's viewfinder, as evident on the Hit and Miss engine, the Maksutov Cassegrain telescope have no aperture adjustment, fixed at f/13.9, and the focus is manual. The SD14 can't even try to talk with the telescope since I need a T-mount to SA adapter to couple them together.

So as long as the light level is good, the SD14 will do the job. For low light, I'll stick with film.

patrickh · Expire: 2011-11-18

Wow - was that conversation in english? Embarassed

patrickh

Personally I just love the colours/texture/acuity of the foveon. But I cannot take the other limitations of the camera - everything is so specific to the Sigma, including RAW processing.

sichko · Joined: 20 Jun 2008 Posts: 2475 Location: South West UK

rbelyell · Expire: 2014-01-31

thanks steaphany. while the jury is still out for me on whether the tradeoffs with the sigma are worth it, your set up seems to work well for you. im not sure if anyone realized how much work seemed to have gone into the photo you posted.

patrickh, i think i may be moving into your camp on this, tho its still too early for me to say so conclusively, and yes one of the negatives i forgot about was lack of alternatives to the awful sigma photo pro pp software--yuk! also, while i initially thought the sigmas lack of bells and whistles would be a badge of honor, its pretty darn annoying when you want to shoot above iso400 and cant, or actually see your images in black and white while youre snapping them!

sichko, your post is the kind of exchange i was hoping for on the tech front--2 opinions where i understand about every fourth or fifth word! Laughing

lulalake · Expire: 2011-11-18

Hi Stephany,
I don't know about the sigma but from all the tests I've seen, the image quality of Canons and Nikons simply leave all digital cameras in the dust, even Leicas.

Here are a few I took last spring at my friends house:

40D various lenses:

His observatory that he built: (20mm Nikon I think)

My daughter and a 14" Meade inside same:(With Disco lights) 10-22 Canon

I piggybacked my 40D on the scope and used a 200mm Jupiter 21A, f8 at 30 sec. (Our old friend the hunter)

Cheers

Jules

Anu · Joined: 14 Apr 2009 Posts: 879

ChrisLilley · Joined: 01 Jan 2008 Posts: 1767 Location: Nice, France

ChrisLilley · Joined: 01 Jan 2008 Posts: 1767 Location: Nice, France

Xpres · Expire: 2014-10-28

From this users point of view - if that's what you mean by 'real life' - the sigma is one tool for a particular job at which I think it excels and that's portraiture. Well, when I want digital anyway. I use one with an Olympus mount and carry an OM4 as well. Printed images do have a film look and are good at A3 which suits me. It also works with my big old vivitar flashes.
And they are cheap...
The technology.... makes my head spin - which I sometimes enjoy but it's the results that I like.

rbelyell · Expire: 2014-01-31

ok, now this is getting good!!!!

anu, i agree the statement canikon leaves everything in the dust is silly. why isnt the statement 'foveon sensors are quite bad by modern standards' not the same silly??!!

as a photographer i am not in the same league as many others here who love the foveon IQ, so while i wouldnt necessarily trust my own judgement in this regard, i do trust theirs!

now if you want to say sigma's CAMERAS are quite bad by modern standards, i can more agree with you. i am finding way too many limitations in the camera compared to their competitors. but frankly the only thing that has kept me from slamming my sd14 into the wall IS the foveon sensor.

lets keep heating this up!!

tony

lulalake · Expire: 2011-11-18

HE HE HE.

Thanks, (it was a fun day and evening)

I judge that on noise and color response. Canon and Nikon (branded CMOS) sensors seem to have the least chroma and luminance noise (at least according to every graph I've ever seen).

The rest is up pretty much to the lens, so a Distagon 35mm on a Sigma will probably do better than a funky AF zoom at 35mm on a Canikon

(except for the Sigma hype and mis-representation of the picture size.)

a 2464 x 1632 picture is an approx. four megapixel image no matter how many sensors are on top of it

Cheers

Jules

Steaphany · Posted: Sat Nov 21, 2009 3:35 pm Post subject:

Sorry for not replying to this thread quicker, I was busy gathering reference material to explain and corroborate the information that I'll be providing.

My sources and references, and getting this out of the way so everyone will know where this information comes from and can verify the material for themselves:

Eyeing the Camera: into the Next Century by Richard F. Lyon and Paul M. Hubel
Foveon, Inc., Santa Clara, California, USA
Published in the Tenth Color Imaging Conference: Color Science and Engineering Systems, Technologies, Applications, CIC 2002, November 12, 2002
The Society for Imaging Science and Technology

Anyone interested in obtaining a PDF copy of this paper can do so from imaging.org, for IS&T members it's free, otherwise the price is $12.00US.

*** DANGER ***
What follows will be a discussion of quantum electrodynamics, I will not be presenting a succession of formulas, common to the patents, patent applications, and texts on the subject, but if you questioned whether prior posts of this thread were English - you have not seen anything yet. The graphs that I'll have posted here have all come from the referenced paper. (Yay - pictures) For those dismayed by "Techno Bla Bla" stop reading now!
*** DANGER ***

Foveon Structure

Here is the conceptual structure of a Foveon photosite:

To anyone versed in Semiconductor Engineering, this structure is nothing new. This is the very same junction profile employed by a NPN bipolar transistor in a junction isolated fabrication process. To those who have played with electronics, this is the magic behind the ancient 7400 TTL logic chips and the LM741C operational amplifier. When I was working in the field of Semiconductor Engineering designing Integrated Injection Logic devices, measurements of transistor parameters would often be distorted by the ambient room light and often a black cloth was used to shield the chip being probed because this effect was not desired.

In this diagram the effect of light absorption is indicated by meters indicating that incident light creates a current across each of the three junctions. This is precisely the phenomenon responsible for a photovoltaic solar panel's electricity production. For anyone desiring a refresher, here is a video from the University of California TV's YouTube channel The Power of the Sun - The Science of the Silicon Solar Cell. ( I do recommend everyone watch this video since it provides a wonderfully succinct explanation of this effect. ) A side note: this phenomenon is so critical to our modern world that this was the discovery for which Albert Einstein won the Nobel prize. His theories of relativity came later and didn't do it.

A cause for confusion in the above diagram is the choice of the word Filter as in "filtering the color components...". In a photographic context, a filter separates incident light through either absorption or reflection delivering a reduction from the incident intensity to the optics that follow. In the Foveon stacked junction structure the layers do not filter, but more accurately possess a characteristic spectral dependent sensitivity:

This diagram shows a Silicon property not touched on by the UCTV video, that the ability to absorb incident photons liberating electrons has a dependence on wavelength, i.e. the left vertical scale showing the absorption coefficient, and that this phenomenon in also dependent on the depth that the photon travels below the surface, i.e. the right vertical scale. An analogy could be chumming for Sharks in the ocean - You throw the chum, an assortment of chopped fish bits, into the water and some Sharks feed near the surface while others let the larger chum bits sink to a depth they favor. For a point of reference, the limit of vision ranges from .4um ( 400nm or 4,000 Angstrom ) on the violet end and .7um ( 700nm or 7,000 Angstrom ) on the red end.

So, what does this chart tell us ? A violet photon with an energy corresponding to a wavelength of .4um is easily absorbed and that this absorption occurs close to the crystal surface. By contrast, a red photon whose energy corresponds to .7um is not as easily absorbed, but more importantly, this absorption characteristically occurs at a greater depth. Some people conclude that since the blue and green sensing junctions are above the red, that the red junction has less photons available to see. This error stems from thinking of the junctions as photographic filters taking light away and leaving less for the layers below, but remember, we are dealing with quantum electrodynamics and an essential property of quantum physics, something that gave Albert Einstein grave concern is the concept of "Maybe". Remember the famous Einstein quote "God does not play dice!" ? Every phenomenon of quantum physics is governed by probability functions, i.e. what is the likelihood of an event occurring:

At this point, I feel I need to explain quantum efficiency. In this chart, quantum efficiency is a measure of the quantum probability for each photon's absorption. i.e. How likely is it that the photon will liberate an electron. If we look at the peaks of the three junctions, we don't have anything any higher than about .325. So, out of a total of 1000 photons, the best we can get is just 325 contributing to a light measurement. What happens to the rest ? Well, they are absorbed, but instead of being helpful by liberating an electron, they just turn into heat. Another example of this phenomenon is when you are out in Sun light. Infrared wavelengths are too weak to liberate electrons, so you feel the effect by your skin warming - Absorbed photons raising the skin temperature. Ultraviolet wavelengths can liberate electrons from the molecules in your skin's living cells which alters chemical processes, i.e. creating vitamin D and causing sunburn.

The overall spectral sensitivity curves are:

This chart also explains an important property of the Foveon imager, of the little bit of light that does constructively yield a measure of light intensity, each junction ends up sensing photons across the whole visual spectrum. The trick is that these three junction measurements need to be transformed into values corresponding the domain of the red, green, and blue primaries. Mathematically, this is a simple Matrix multiplication, but, because of the degree of overlap, the transformation matrix must mathematically combine all three junction measurement values together for each primary color. This is where the poor low light performance stems from, yielding severe noise in low light and night images and noisy shadows in normally lit scenes. I'm not saying that the Foveon imager itself is noise free, but the architecture has issues which would be very difficult to over come completely.

I hope that I have achieved at least a bit of understanding that the Foveon imager does see color, admittedly poorly, but still well enough for photography. That the quantum efficiency of the junctions show that the deeper junctions don't suffer from a lack of light. That the noise issue is less a factor of the silicon but more dependant on what needs to be done mathematically with the data afterwards.

When researching whether or not to go with the SD14, it was coming to the above understanding that sold me on the technology. Yes, I knew what I was getting myself in for when I purchased my SD14.

And... I'm not done yet. Wink

Just to show that I need a performance level of technology rather than brand name, here is a stacked photosite technology that Nikon has developed:

This diagram comes from US Patent #7,138,663, Color separation device of solid-state image sensor. Instead of applying a Bayer filter mask to the imager surface, a primary separation array of dichroic mirrors is applied to the chip. Incident light is focused by a microlens through a small aperture in an opaque mask covering the chip and dichrioc mirror array. The dichroic mirrors of each photosite separate and distribute the red, green, and blue light to the respective photoreceptors. In theory, this would yield a clarity and resolution of a Foveon with better sensitivity and with less imager noise and with out the data manipulation induced noise.

Then, why don't I have a Nikon camera ? Nikon tech support !

Curious about this technology, I contacted Nikon Support and, oddly enough, they answered.

My inquiry:

Anu · Joined: 14 Apr 2009 Posts: 879

rbelyell · Expire: 2014-01-31

anu, stay inside, we dont want you to be porridge for polar bear!

and while you are inside you might want to take a look at some of these silly resolution charts that people are so fond of and see that foveon has really great resolution (according to dpreview) compared to similar cameras and even compared to theoretically better cameras.

now i personally hate that stupid chart stuff, because as a really good photographer i know said, 'i dont shoot charts'! Smile

i have always thought you can get too far from the real world mucking about in these silly tests, but i will cite it here as it proves my point about foveon resolution! Laughing

as for color, i think color is subjective, and frankly i think there are many people who dont have a foveon who love the color of foveon--many in this forum. count me among them. to say aps-c objectively beats foveon on color is to quote a great man i post with 'silly' Laughing

you win on noise; 'nuff said.
t

lulalake · Expire: 2011-11-18

I don't like the oversaturation of Velvia all that much, nor do I like the oversaturation of the Foveon all that much either.

Cheers

Jules

Anu · Joined: 14 Apr 2009 Posts: 879

sichko · Joined: 20 Jun 2008 Posts: 2475 Location: South West UK

patrickh · Expire: 2011-11-18

Steaphany
Awesome

Others - this is a fascinating thread even if I only understand one concept out of ten.

patrickh

I remember in the early days (about 4 - 5 years ago) some (and I stress the some) results from the foveon were almost the only ones to compare favorably with film. It was an attractive aspect of the sensor. Nowadays, whatever edge it may have had has long been dissipated by a lack of development on the foveon front and the improvements in sensors under the old Bayer regime. Not to mention software of course...

rbelyell · Expire: 2014-01-31

first i have really enjoyed the twin debates in this thread; one ive been a part of and another ive enjoyed from afar--intellectually real afar. Laughing

my ability to provide meaningful advancement of either is nonetheless coming to a close. anu, i would love to hear what you heard about the colorchart experiment, but unfortunately i dont have any such chart or facsimilie thereof to confirm/dispute whatever result you have in mind, sorry. Sad

i view the advanced technical debate in this thread as dovetailing nicely with my debate with anu, because at the end of the day, better minds than mine can look at the same technical data and reach very different conclusions; better eyes than mine can look at similar images, taken with different cameras or different sensors and also come to very different conclusions.

while we believe we make hardware decisions with our 'head', the truth i take from this thread is that, no matter how hard we try, photography is NOT a science, its an art. as with all art, beauty is in the eye of the beholder, within reasonable bounds its almost totally subjective. i think at the bottom of it we may buy new cameras, admire others, covet others because of what we read about them, but we SELL some and keep USING others because of how we FEEL about the pictures taken with them.

maybe patrickh had it right re foveon--its been stuck in the same technical place for several years while other technology has advanced and thus the foveon advantage has passed. to my eye, and to a school of others, i still see a difference in depth, in feel. might i trade that in for better resolution, for an easier user experience, for better out of the camera results--yeah i might. do i understand why others wouldnt make the same decision--absolutely. would i try to convince them to my point of view with technical arguments--no because i dont think technical arguments convince anyone to stop using a camera that produces images they like.

thanks to anu, patrick, steaphany, sichko etc as i really enjoyed the debate!
tony

sichko · Joined: 20 Jun 2008 Posts: 2475 Location: South West UK

Anu · Joined: 14 Apr 2009 Posts: 879

rbelyell · Expire: 2014-01-31

anu it was fun debating with you, but i think absolute statements, like the foveon advantage was a myth, are, to quote you, just silly. there is no absolute science in this as is perfectly exemplified by steaphany and sichko going back and forth differing over their subjective analysis of the exact same technical data. we pretend there is science to justify our subjective opinions, perhaps because we are insecure about them. i dont need to point to something external to justify my choices, nor do i feel it necessary to take my subjective analysis of technical data to prove someone else's choice of hardware is inferior. there is a whole community of very good photographers, and very good engineers, who think your analysis of foveon is full of beans. doesnt mean they're right; doesnt mean you're right; means there really isnt a 'right'.
tony

scsambrook · Expire: 2011-11-18

Fascinating thread ... I'm not really sure I ever fully understood the technicalities of black & white emulsions and chemistry, so some of this is really rather beyond my ageing brain Embarassed

On a slightly different note, I do think Nikon's responses to a technical question and personal observation were - to say the very least - patronising and dismissive. There ARE polite ways to fend off questions you don't want to answer. But then, would Canon, or Pentax, or Leica, or anyone else have been any more informative?