Photokina 2010, Pentax and the full frame mystery

Only a few days left until Photokina 2010

Or why at this year's 2010 Photokina exhibition, Pentax may not get
away with ignoring the full frame conumdrum.

Many users of digital SLR cameras may not be aware that the sensor in their
camera is smaller than it used to be in the era of 35mm film. Most dSLR cameras
use an APS-C sized sensor which does only have about 40% of the surface of
a "full
35mm film frame", or "full frame" in short.
Of course, this is expressed by the crop factor and users actually do know
about this. They simply ignore this. And they have reason to do so: the image
quality exceeds that of full frame film cameras and therefore, there seems
to be no reason to care about the detail of sensor size for a dSLR camera.

But as always, there is a school of photograhers who do not agree. It can
be shown that a larger sensor -- when combined with lenses which fully exploit
the design options offered by a larger sensor -- delivers superior image quality.
Independent on how great it was in the first place. After all, it's the reason
of digital medium format cameras to exist. Moreover, the lens mount of all dSLRs
with an APS-C sized sensor is desgned for full frame lenses (lenses with an
image circle large enough to use the entire surface of a full frame sized sensor).
Simply because those mounts are from the 35mm film era. And because it is the
mount (diameter and registration distance) which determines the majority of
the size of an SLR camera, a full frame dSLR wouldn't need to be (significantly)
heavier
or
bulkier
than
an APS-C
dSLR.
Four-Third sized SLR cameras are an exception as their mount isn't full frame
capable. But we can savely ignore it after the impact of this sensor size on
the SLR market has almost vanished after the introduction of Micro Four-Third.

The opening photo is that of a Pentax APS-C dSLR certainly bulkier
than any full frame Pentax film SLR has ever been. Actually, the famous 30+
year old Pentax MX full frame film SLR is smaller than any digital SLR on the
market today, whatever small be its sensor. A full frame dSLR could certainly
be made more compact than the APS-C dSLR shown on the photo above.

So after dismissing the size disadvantage, we are left with only three arguments against a full frame camera which
all disappear on closer inspection, too:

1. Full frame sensors are too expensive and only pros
   can afford it. Right?

   
   Well, from public cost models I computed upper bounds
   for
   2010 manufacturing costs for APS-C and full frame sensrs and the difference is
   less than $100 (*) ! Of course, semiconductor vendors will
   add significantly different margins as long as this
   market doesn't heat up.
   

   (*) Note: for all claims made in this article, look up the "Furter reading" section at the end of the article for further reference.




2. The lenses are too expensive, bulky and heavy. Right?

   
   Well, equivalent lenses (different lenses but such that
   they provide equivalent image quality for different
   sized sensors) have the same size and weight for APS-C
   and full frame. And are a bit less expensive
   for full frame! Which is easy to explain by looking
   at lp/mm resolution requirements.




3. One needs longer, heavier, more expensive tele lenses
   because one looses the crop factor. Right?

   
   Well, about heavier and more expensive, read above. About
   longer, that's actually a function of the pixel pitch,
   not the crop factor. There is no reason why a full frame
   camera should have a larger pixel pitch than an APS-C
   camera. Currently and for cost reasons only, most actually
   do indeed. Although the difference is already as small as 5µm vs. 6µm. And it is going away. Read about the cost factor above.

So, we are left with a situation where a full frame SLR
should be a no brainer. But as always, things aren't as
simple as they appear.

 

Market segmentation

Because full frame cameras can deliver better image quality
they appeal to a higher segment of the market. The so-called
enthusiast and professional photographer markets. There
is a hidden consensus between Japanese camera makers (with
maybe the exception of Sony) to draw excessive margins
from the full frame market. Therefore, full frame dSLRs
are either prohibitively expensive (Nikon D3X, Canon 1DsMkIII) or crippled
in one way or another. Sometimes not voluntariliy (Sony).
And they are all bulky and ugly because they have to show
"full frame inside", right? ;)

But despite all the artificial barriers to keep the
markets segmented, more popular models like Canon 5DmkII
or Nikon D700 have risen to 2-3% unit market share each
(estimated from BCN figures). Adding the many professional models from
Canon
and Nikon and the very affordable Sony A850 we have
a unit market share of full frame dSLRs of 5-10%.
Of couse, each new model sends shock waves thru this segmentation
and an upgrade to the D700 is expected
later this year. The figures do also mean that full frame
dSLRs create a significant portion of the vendor's overall
margins,
possibly in excess of 30%.

Overall, the dSLR market is in a state like a supercooled
fluid: the right perturbation and the segmentation will
implode and all but the entry-level SLRs go full frame
(the entry-level SLRs go mirrorless Single Lens Digital
(SLD) anyway...). Think of a full frame Canon 7D or Pentax
K-7 in terms of ergonomics and speed, for well below $1800
settled street price ...

 

Pentax and the Full Frame mystery

Pentax is an interesting special case. They have not offered
a full frame dSLR yet and always denied any plans to launch
such a camera. On the other hand, Pentax is the brand of
the image quality perfectionist and landscape photographers.
Pentax was the first trying to launch an enthusiast full
frame dSLR, back in the year 2000 (the famous 6MP Pentax
MZ-D), three years before they launched their APS-C dSLR.
They were the first to promote weather sealed bodies and
lenses
for outdoor photography, the first to offer a 15MP APS-C
dSLR (the Pentax K20D) and they are even first to offer
an enthusiast digital medium format SLR below $10,000
(the Pentax 645D). So, they shoud be predestined to offer
the
first
ergonomic
outdoor 20MP+ full frame dSLR in the enthusiast market
segment (~$1200 to ~$1800). This could make
their market share explode.

But there are problems: Pentax burned fingers when trying
to be full frame in 2000. And they burned bridges when
later launching their APS-C only line of dSLRs. Because
for 5 years, they developped APS-C lenses
only and assured the market that their lens investments
are safe because full frame cameras won't come back. In
mid 2008 though, they seem to have changed direction again
and almost no new lenses have been introduced. Two new
lenses, introduced in 2008/2009, the DA*300 and the
DA*60-250/4, are patented as full
frame lenses, actually. So, who knows ... But at least
officially, Pentax is now short in full frame lenses. And
because they never left the decision between APS-C and
full frame to their customers, any announcement about a
forthcoming full frame camera could stall their on-going
business. Well, Pentax may even fear to cannibalize their
new digital medium format business which seems to have
a bright future.

Most importantly though and because they burned fingers
once, Pentax may be convinced that their share of the full
frame market is simply too small, like 5% of 5% or 0.25%
only.

And if deciding to divert development resources, they
may as well decide to invest into the SLD market to protect
their cash cow.

So, when looking at the current or past situation, there
is no reason for Pentax to launch a full frame dSLR camera.
But what about when looking into the future?

This is were the community of Pentax photographers (called
Pentaxians by Pentax) comes into play.

 

Pentax and the year 2011

2011 will be the year where everybody sells SLD cameras,
Pentax included. Everybody. Pentax will have a genuine
SLD camera. As will Canon and Nikon. But where are buyers
coming from? Well, mostly upgraders from the dying point
& shoot market (in majority shifting to cell phones) and
migraters from equally priced (i.e., entry-level) dSLR.
So, to launch an SLD camera is vital to preserve a market
share in the $400 - $800 segment. Exactly where the Pentax
K-x attracted new buyers to Pentax in the year 2009. But
all
of this doesn't help to preserve the enthusiast (Pentaxian)
market which is the $900 - $1800 segment.

One may argue that the enthusiast market isn't that important
for Pentax from a point of view of turnover. But according
to my own analysis, K-x, K-7 and 645D each create about
the same amount of earnings. Simply because
the mass markets are always small in margin. But most importantly,
blogging Pentaxians are the most influential group: they
are opinion leaders in forums where magazine authors and
store managers draw their opinion from and recommend some
products or not. Unlike in previous years, this group
of opinion leaders has expressed very clearly that they
either expect to see Pentax going full frame in the enthusiast
segment, or leave the brand. I refer to bloggers like LanceB,
once selected "Pentaxian of the year" and who now test
drives a D700 before taking final action.

Pentax is already seeing that Pentaxians put themselves
onto "hold and wait": The sale of expensive DA lenses has
declined while the market for used (full frame) FA and
A lenses is still healthy. This isn't only due to a lack
of new DA* lenses. It is mostly due to the fact that the
enthusiast market drives lens sales and Pentaxians now
assume that the "never be full frame" claim of Pentax lost
its
credibility (due to technical arguments as outlined above).
After all, purchasing a lens is much more kind of an investment
than purchasing a camera which is known to deprecate
fast. The full frame conundrum is already destroying half
of Pentax' business.

So, what would be the right actions to be taken by Pentax
in 2011? Well, first, join the P&S and part of the SLR
team into a new SLD department, delivering the world's
first water-proof SLD and making sure a K-mount adapter
with AF support exists. Drop the P&S division. Pentax'
SLD mount should look as close as possible to Sony's E-mount,
allowing
for
future
35mm SLD cameras. Possibly allowing to sell Pentax lenses
for the E-mount too. I assume the E-mount uses an encrypted
communication protocol. But at least mechanically, there
should be fit.

Second though, form a team from remaining SLR and
645D developers for enthusiast cameras. Their first product
shall be a 24-35MP full frame SLR with Exmor HD
sensor in a K-5* body. Third, release new full frame lenses,
like the DFA 100/Macro relaunched earlier this year.

One may argue that this is infeasible. At least for the
second "enthusiast" team, I don't think so. Assuming Sony
would share their full frame Exmor sensor with Pentax,
all the rest is routine work for Pentax engineers. Moreover,
in June 2008, a Pentax manager said in an interview
that the development of a full frame camera is in its planning
stage. So, if that project wasn't cancelled, it should
be ready to deliver by 2011. Even taking into account that
K-7 and 645D diverted valuable resources in the first 2
years of the 3 year period. Surprisingly, the "leaked"
full frame project coincides with a rush of completed APS-C
DA lenses (2008) and a complete halt to new APS-C
only lens releases from then on and until now (with the
exception of the DA15 lens). Therefore, I guess that Pentax
would have enough full frame lenses to accompany the release
of the camera: FA31, FA43, FA77, DA*55, DA*60-250, DFA100,
DA*200, DA*300. With only 4 additional lenses (DFA28-80
kit zoom, a DFA~18 wideangle prime and two f/2.8 DFA* zooms
(24-70
and
70-200)), the lens line up would be fairly complete. Four
lenses developped or optimized in 3 years, why not?

 

Pentax and Photokina 2010

Photokina 2010 starts September 21 in Cologne, Germany.
It is the event and everybody is watching
Pentax there (if at all). The internet's rumor mill has
a pretty detailed prediction about what Pentax is going
to reveal: A K-x successor (with focus indicators) and
a new camera positioned above the K-7 but not replacing
it. The first camera named K-r, the second K-5. The K-5
would be APS-C but with a 16MP Sony Exmor sensor, faster
fps (7?) and faster AF system in a body similiar or identical
to that of the K-7. At a price spot at the lower end of
the enthusiast market segment. No full frame. No SLD.

But I sincerely fear that this doesn't suffice. Starting
at Photokina 2010, Pentaxians need a roadmap to full frame
and corresponding lenses in order to be able continue to
invest into their system. They have harvested enough money
now to either invest or migrate elsewhere. And Photokina
2010 will be the checkpoint for many to take action.

To stay silent at Photokina on the full frame front may
imply suicide for Pentax in the mid term.

Pentax can wait until 2011 to say anything about SLD.
People waiting for SLD aren't the opinion leaders so letting
them wait doesn't hurt. Moreover, they can buy any other
SLD w/o leaving the Pentax system. But to disappoint the
enthusiasts now is more dangerous than it ever has been
before. Up to the point that a K-5 would only sell if the
roadmap to full frame is sufficiently clear. Which sounds
paradox but isn't. It's all about psychology and the comfort
zone for what appears to be a hobby for most Pentaxians.
Pentax has to make Pentaxians believe into the brand. That's
part of their job, actually!

So, these are my recommended action items for Pentax at
Photokina 2010:

• Announce K-5


• Launch K-r


• Publish a road-map to full frame, with a first delivery
  in 2011.


• Launch new lenses, maybe one for APS-C and two for
  full frame.


• Keep the SLD project a secret.

This article may be read as an open letter to Pentax.
Pentax has no plan to say anything about full frame. Which
is a severe mistake. Seize your chance. If you're too late
to the party, there may
be nobody
left
to become
enthusiast
about
;)
So, keep
people dancing ...

 

Further reading:

• Leaked
  information about Pentax K-r and Pentax K-5 ff.


• Leaked information about Pentax SLD project.


• Full
  frame patent of DA*300/4.


• Full
  frame patent of DA*60-250/4 (note: on full
  frame, the 60-250 has slight vignetting and drop of
  corner
  sharpness
  at the tele end
  which can be cured in post-processing; work tba).


• 2008
  leak of planned full frame project (by Shibata,
  Chi Ho).


• Suitability
  of various Pentax lenses labelled DA for full frame.


• Release
  date gap for APS-C only DA lenses.


• True
  manufacturing cost of a full-frame sensor out of fab.


• About lens equivalence, article endorsed by LumoLabs.


• BCN
  market share by camera model in H1/2010 (no full
  frame releases in this period).



• note: no information received in private communication
  has been made public in this article!

You may use the commenting section to express your endorsement.
Thanks for reading!

 

LumoLabs: Shutter-induced blur with an SLR camera

A recent observation made by us and others was that shake reduction efficiency for the Pentax K-7 camera seemed to have a weak spot around about 1/100s and less. Something nobody could really understand and not everybody was able to confirm.

Therefore, we decided to try to answer an old and fundamental question for SLR photography: To which extent does the mechanical focal plane shutter and the mirror slap negatively influence image sharpness? Especially in the digital age with its theoretically rather high image resolution. We, this means two friends (Henning and Rüdiger) and myself (Falk). And of course, we decided to focus our study to the Pentax K-7 SLR camera in order to provde an answer to the observation mentioned above.

The short story is that we managed to find the answers. All our findings are written down in detail in a LumoLabs White paper:

-> http://www.falklumo.com/lumolabs/articles/k7shutter/index.html.

Please refer to this document to actually understand the work we have done. In the following, we will summarize our findings without explaining how we got there. However, note that 4 different camera bodies, data from 4 testers, 8 lenses and two firmware versions have been used. More than thousand test shots and several thousand accurate blur data measurements have been aggregated. High speed video, acoustic recording and acceleration measurements complement the data. So, we assure that the result describe the general behaviour of a Pentax K-7 SLR camera. Pentax has obtained a copy of the paper to be used at their discretion.

We will make no statement about how the results relate to other SLR cameras. Except for a quantitative comparison with one Pentax K20D SLR camera.


Results:

1. The mechanical focal plane shutter indirectly can increase the blur in an image. The exact amount of additional blur depends on the direction in the image. It is zero at a vertical contrast edge (aka yaw blur, blur due to yaw movement). And it is up to 11 µm (on average) at a horizontal contrast edge (aka nick blur, blur due to nick movement).
   
   The exact amount of average blur is shown in the opening figure of this article. It has its maximum for shutter speeds of about 1/100s to 1/80s. It is less than 5 µm for 1/25s and slower. Or 1/250s and faster.
   
   Note that any single image can be affected more or less. Add or subtract +/-50% to get an idea of variation from image to image.
   
   Note that one pixel is 5 µm large and the blur effect is only visible if all other sources of blur are very well under control (sharpening, defocus, shake, subject blur, lens abberation, noise etc.). Normally, these other sources mask the effect. Nevertheless, if you want tack sharp images then you need to understand the shutter blur effect.
   
2. The effect for the Pentax K-7 is larger than for the Pentax K20D. About 2 - 3x larger.
   
3. Mirror slap or shake reduction have no negative or positive impact on the effect. Shake reduction works as advertized but cannot counteract the perturbation from the focal plane shutter as it is too fast really. Mirror slap is very well dampened in the K-7 camera and has no negative impact on image resolution except on a weak tripod.
   
   There is a delay of about 10 ms between end of mirror slap and begin of shutter operation which suffices to keep the mirror slap perturbation out of the image.
   
4. The blur effect is an indirect one:
   
   First, the moving masses of the shutter (curtain etc.) make the body move (with surprising speed and acceleration of its stiff body!).
   
   Second, the body movements cause a classical blur effect lasting as long as the shutter works. The K-7 shutter is faster and stronger than that of the K20D probably increasing the effect by some 60% or so.
   
   Third, the body accelerations cause additional vibrations in the imaging sensor which last a bit longer than the first shutter curtain operates and which magnify the effect by another 60% or so.
   
   Preventing the first from happening (which requires a heavy and sturdy tripod) will kill the effect. There is no "loose" magnetically held imaging sensor and no negative direct impact from shutter curtain or mirror slap causing air flow in the mirror box or whatever.
   
5. In practice, you'll only see any effect with wide angle lenses.
   
   At about 1/100s you would normally have blur due to free-hand shake (we can ignore the case of a tripod as only weak tripods would cause any trouble with the shutter). At 50 mm and longer, the shutter blur will be masked and at 30 mm it will have comparable magnitude. It is at 10-20 mm that the effect will be noticeable most.
   
   In these cases, we highly recommend to shoot at 1/25s (or slower) and to enable shake reduction as it is highly efficient at such exposure speeds. The images will be sharper than at 1/100s!
   
6. Early efficiency tests of the K-7 shake reduction suggested that it may be ineffective at fast shutter speeds as required for long focal lengths. This was a preliminary conclusion we proved to be wrong.
   
   The Pentax shake reduction is effective even at 1/500s! It just cannot prevent the shutter blur at about 1/100s. We may soon publish an update to our SR guide reflecting this.

So, here you have it in a nutshell. Please, refer to the full paper before asking questions. The paper is available as HTML and PDF (linked from the top of the paper). It is recommended to download and read the White Paper on "Understanding Image Sharpness" first.

UPDATE (2010 July, 28):

We checked if the new firmware release 1.10.00.25 released earlier today brought an improvement. The answer is NO.

We've run a number of measurements and within the limits of our very good measurement accuracy (about 0.10 to 0.15 pixels error margins) we cannot see an improvement.

[end of update]

Frequently Asked Questions:

Q: Did you study the K-x, do you know if it has a similar effect?
A: No. But anybody is invited to replicate our study for the Penatx K-x :)

Q: Is the shutter blur in the Pentax K-7 a defect?
A: No, any SLR shutter for any make causes blur to some degree. We just wished for the Pentax K-7 that it would be as small as it is for the K20D. We publish this partly to remind all camera makers that we watch their work ;)

Q: Does switching off shake reduction lead to sharper images?
A: No.

Q: Does mirror lookup work around shutter blur?
A: No.

Q: Does a tripod work around shutter blur?
A: Sometimes. If it is rock solid. A normal tripod most likely won't help much.

Q: Why does a longer exposure time work around shutter blur?
A: Because during the majority of the exposure, the shutter won't move and what you get is an average blur.

Q: Why does a shorter exposure time work around shutter blur?
A: Partly, because there simply is less time for anything to blur. Partly, because stimulated vibrations cause no harm after the shutter already closed.

Q: May I ask questions without reading the White paper?
A: No.

Q: But I don't understand the White paper!
A: How do you know without reading it? ;)

Q: Will you win a Nobel price for this crazy shit of work?
A: No. Alfred Nobel forgot photographers ;)

Further reading:

• Understanding Image Sharpness White Paper
• Understanding Image Sharpness White Paper PDF
• Shutter-induced blur with an SLR camera White Paper (this work)
• Shutter-induced blur with an SLR camera White Paper (this work) PDF
• Why the lens has little effect: Theory of pitch and shift of a camera+lens combination in reaction to moving shutter mass (PDF)

Enjoy the read ;)

Philipp Lahm Wedding

Philipp Lahm is team captain of German national FIFA football team, who just scored third place at the FIFA world championship in South Africa.

First thing he did when he came back to Munich was to marry his bride, Claudia Schattenberg. And as luck would have it he selected the St. Emmeran church of Kleinhelfendorf to do so. Just some of hundred meters away from where my studio is located.

So, I decided to play paparazzo and see what I could grab as a photo.

No question that about hundred true paparazzi were blocking my sight and -- as the number of them exceeded the population of Kleinhelfendorf ;) -- theirs as well. I can only say:

Bring your own ladder!


I am glad I don't have to earn my money this way. As soon as the bride entered the church, they started to run each other over in an attempt to be first to upload the photo. Of course, the 3G/UMTS infrastructure of Kleinhelfendorf wasn't really meant for this use case. To see scores of paparazzi left in frustration is a priceless experience :)

Also, chatting with some of the photographers, TV teams and moderators was interesting. I now have a better idea of the amount of money changing hands on events like this. Needless to say that the right to officially take photos was sold exclusively upfront.


Despite the competition for sight, I tried my luck and here is what I managed to achieve. Enjoy :)


















(Click on the images to enlarge. All photos © 2010 Falk Lumo. No reprint or linking without permission. All and more photos available in high resolution.)

Just a closing remark after you have seen the images... I used my mountain bike to be ahead of the horse drawn wedding carriage on its path thru small and rural roads. After a few kilometers only I've seen no more paparazzi photographers. They don't try as hard as one would imagine... ;)

LumoLabs: Understanding Image Sharpness

We have prepared our first White Paper. It shall serve as a base to better understand our methodologies to measure image resolution and more importantly, it is meant to help understand what factors can prevent an image from turning out tac-sharp.


LumoLabs website

We changed the layout of our site too.

LumoLabs is now at www.falklumo.com/lumolabs and hosts a repository of articles.

Therefore, we will use the blog to announce new articles or important updates to followers and interested parties. And to enable their discussion.

The actual articles are not posted as a blog article as its format was deemed unsuitable. But you'll find links to both the online article and a printable PDF version. If possible, we always recommend to download and read the PDF version. The PDF version does update more frequently too ;)


Understanding Image Sharpness


(Sample chart form the article)
Hint: The article image URLs actually open as larger images as they appear embedded in the article.

This article is a recommended read for anybody loving to dig into technology and who isn't afraid of a bit of math.

It's abstract and table of contents is:

Abstract
This White Paper is one in a series of articles discussing various aspects in obtaining sharp photographs such as obtaining sharp focus, avoiding shake and motion blur, possible lens resolution etc. This paper tries to provide a common basis for a quantitative discussion of these aspects.

Table of Content
1. Measures
1.1. Modular Transfer Function
1.2. Blur
1.2.1. The hard pixel
1.2.2. The perfect pixel
1.2.3. The real pixel, sharp and soft
1.3. More realistic resolution measures
1.4. Combining blur
2. Sources of blur
2.1. Defocus
2.1.1. Ability of deconvolution operators to reduce defocus blur
2.2. Bayer matrix and anti aliasing
2.3. Diffraction
2.4. Lens aberrations
2.4.1. Defocus, Spherical aberration, Coma, Astigmatism
2.5. Shake
2.5.1. Measuring shake
2.5.2. Expected shake
2.5.3. Empirical results
2.5.4. Tripod classification
2.6. Motion blur
2.7. Noise
2.8. Atmospheric perturbations
2.9. Precision and calibration
3. Practical considerations and examples

Please, proceed here:

• Online article (same as click onto blog title)
• PDF print version

 

Apple iPhone 4 camera specs

On 2010, June 7 His Steveness has introduced the Apple iPhone 4 which features a new camera module. Two actually but I am going to talk about the main camera (on its rear side) only. And only about its still photography capabilities (it records 720p 30fps HD video as well).

It is typically hard to figure out the exact camera specification for cell phones and to compare them with a P&S camera. E.g., the HTC EVO 4G is said to have an 8 megapixel camera but little else is known. Images shot with the EVO all lack the significant EXIF information!

However, I think I managed to extract the full iPhone 4 camera specs now.

First, the pixels are 1.75 µm (according to Job's keynote) and we may assume that this is the pixel pitch. Sample images are 2592x1936 pixels (5.0 MP, 4.02:3). This makes a 4.54 x 3.39 mm^2 chip (5.67 mm diagonal) which corresponds to a 35mm film camera crop factor of 7.64.

In a P&S, this would be called a 1/3.2" sensor and P&S sensors range between 1/3.8" and 1/1.5" (crop factors between 8.6 and 3.9). So, it is an imaging sensor at the lower end of the P&S range, but it is in the P&S range and with a reasonable number of pixels and a back-illuminated sensor like the Sony Exmor R sensor. Here is a sample image from Apple's web site:


(click on the image for the sample in original size; hosted on apple.com)

Gizmodo.de has published the full EXIF data for exactly this sample photo (it is magically absent from the web sample though ...):

Aperture: 2.97
Color space: Uncalibrated
Date and time: 2010/05/07 15:14
Exposure: Auto exposure
Exposure time: 1/887
Flash: Flash did not fire, auto mode
FNumber: 2.8
Focal length: 3.85
ISO speed rating: 80
Metering mode: Spot
Sharpness: Hard
White balance: Auto

So, the lens is a 3.85 mm f/2.8 lens.

This corresponds to 35mm film camera equivalent lens of 29.4mm f/21.4.

I should note that even an aperture this small is not restricted by diffraction yet (limit at f/2.8 is at 54% of pixel width). This is a good value. But one really shouldn't stop down beyond f/4 and it seems the iPhone 4 has an f/3 fixed aperture lens anyway.


Summary

iPhone 4 main camera:

• 5.0 Mpixels (2592 x 1936)
• 1/3.2" back-illuminated CMOS sensor
• 4:3 aspect ratio
• 35 mm film camera crop factor: 7.64
• Low ISO 80 (or better)
• 3.85 mm lens focal length
• f/2.8 lens aperture
• Autofocus: tap to focus

Equivalent 35mm film camera and lens:

• 30 mm f/22

So, don't throw away your FourThird, APS-C or full frame SLR ;)

Besides the deep depth of field, an f/21.4 aperture at ISO 80 produces as much noise as an f/8 lens at ISO 570 (for a given shutter speed). Where 35mm film camera f/8 and APS-C f/5.6 produce the same level of noise.


Conclusion

The iPhone 4 seems to have a camera which should deliver an image quality on par with the lower segment of P&S cameras. It's field of view (no zoom!) corresponds to a 30mm lens (on a 35mm film camera) and it captures as much light (produces as much noise) as a system camera with a lens aperture between f/11 (FourThird) and f/22 (35mm film).