Full Frame Lens and FF Sensors!

[jamesm007]

Pentax has been making cameras since 1919 and in 1952 Pentax made the first SLR camera! In 1971 Pentax came out with the first multi-coated lens; its now famous SMC (Super Multi Coat). Around 1975 Pentax came out with the K mount. Since that time until pentax stopped making film SLRs Pentax produced millions and millions of lens that are in peoples homes around the world.

Pentax kept its old K mount that let everyone use all those millions of lens just sitting around. Moreover they made those old lens easy to use with the “Green Button”. What this button did was meter for you even in manual mode!

Full frame is a bigger size than APS, and some photographers want Pentax to make full frame dSLRs again just as Canon and Nikon are making today. They feel Pentax is missing the boat or that it will make a more complete system. One reason is all of those millions of lens were designed for 35mm or full frame size film. So naturally why not make a full size sensor? Why does Pentax hold on to APS only for SLRs as of today?

Maybe this is one of the reasons -

It could be that 10 years ago Pentax tested and found what Klaus, owner (and tester) of the lens testing site Photozone found. Many, a good percentage of older film lens don’t work well with full frame sensors. The reason is film was forgiving of the angle light was hitting it (see examples below) film is a thick media compared to digital sensors. To help visualize the difference think of film as a piece of paper and a pixel of a sensor as a piece of paper down in a cup 3” round and a three inches deep with the paper at the bottom. Now imagine the light source a ceiling lamp but you your cup and paper are in the corner of the room. Which paper would receive the most light? Of course it would be the paper out in the open. Scientist have made bubble type lens that sit on top of the cup to help capture the light at the edges and corners but it still falls well short of film and there is a light loss.

Now what’s a good way to make all those millions of lens perform well in a digital sensor? Make a smaller room (in the analogy above) so the light hits the cup at less of an angle. And that’s what Pentax has been doing by staying with APS sensors that are 1.5X smaller than FF. It allows the best performance out of those older lens that are not made for the extreme demands of digital sensors. There is more to the benefits. Even if light did strike a FF digital sensor perfect, cropping out the edges leaves the best image quality produced from lens. That’s in the center then boarders, corner are worse but are cropped out with APS sensors. So it’s a double benefit by using APS sensors with older full frame lens. You eliminate the light loss in the corners and crop out the worse part of a lens image quality. For telephoto fans you also make it 1.5X longer e.g. 50mm is 75mm, but wide angle fans lose 1.5x!

Some reference and quotes for you to read and study. Look at all the older full frame lens tested at Photozone on full frame dSLRs. There is at times an extreme light loss in the corners.

“ The vignetting characteristic is somewhat critical. At max. aperture we're talking about an edge shading of about 2.9EV which is fairly extreme. Such a "key hole" effect is already difficult to correct without artifacts. The situation improves at f/5.6 ( about 1.8EV) but you should really stop down to f/8 to tame the problem to an acceptable level.”

“The Voigtlander gave us somewhat mixed feelings regarding its resolution potential. The center quality is very fine even at f/3.5 and the borders are quite good here but the corners are plain soft.”

Klaus of Photozone testing Voigtlander Color Skopar 20mm f/3.5 SL II on Canon FF

http://www.photozone.de/canon_eos_ff/504-voigtlander20f35eosff?start=1

“Fast lenses tend to suffer from high vignetting on full frame cameras and the AF-S 35/1.4 is no exception to this rule. In fact, with almost 2.2 EV wide open the amount of vignetting is exceptional (in a negative sense) and higher than on any other lens we've measured so far on the D3x. Such a huge amount of corner darkening is of course clearly visible in the final image.”

Klaus of Photozone
http://www.photozone.de/nikon_ff/596-nikkorafs3514ff?start=1

Here is an article that I found to post reference and it’s a good read. Here is a quote then link.

Corners on wide-angle and open apertures. When examining a wide-angle picture shot with a Canon full-frame dSLR, Nikonians like to giggle and point at the corners.Indeed, often, there is something to giggle at. I do not know of any ultrawide (say, 20 mm and below) that will produce impeccable corners on full-frame digital at all or even most apertures. On the other hand, the reduced-circle ultrawide zooms from Canon, Tokina, Sigma, and Nikon (that 12-24 DX is absolutely gorgeous!) are more consistent than anything comparable for full-frame, even near-legendary glass like the Zeiss Distagon 21/2.8

http://www.prime-junta.net/pont/Pontification/a0100_Full_Frame_or_Not/a_Full_Frame_Or_Not.html

Pentax did the right thing 10 years ago. They made it so you can use your FF lens and get superb Image quality. Now some want more. Which is natural. But think about what Pentax gave. Pentax has known for years full frame makes its older lens not so good anymore and will have to develop a lot of new FF lens! But people have begged for FF. Just know that a good percentage of those old lens won’t perform near as well or even poorly compared to the same lens on an APS sensor dSLR. Sometimes we don’t know what’s best for us. Or the truth.







--
jamesm007,

http://www.flickr.com/photos/jamesm007/
http://s195.photobucket.com/albums/z77/jamesm700/

 

[DS21]

Very interesting perspective. How do modern FF lenses deal with this problem, the angles and sensor surface are the same for both new and old FF lenses, what is the modification that makes modern FF lenses better? Is it just the coating to reduce reflections from the back even more, or they reduce the angles by making the lens physically longer for the given focal length?

 

[Sean Nelson]

This was an issue in the early days of digital sensors, but technology has moved on. Sensors that must deal with light striking the sensor at low angles of incidence now use microlenses positioned just above the pixels to direct light down into the pixel wells.

The proliferation of mirrorless cameras with very short register distances stands as evidence that this no longer the problem it once was.

 

[DW75]

Nice post. I'm personally not too excited about a FF Pentax and I don't think I'll buy one. I like my Pentax gear because it's small and lightweight.

Should Pentax add a FF camera? I don't know. It will provide an upgrade path and may prevent people from migrating to Canon and Nikon just to get full frame. But Pentax is a small company. Can they really simultaneously develop 645, FF, DX, and the Q series at the same time? Will it prevent them from releasing DX lenses that should be in their lineup but are missing, such as a weather sealed ultra wide zoom?

 

[viking79]

The proliferation of mirrorless cameras with very short register distances stands as evidence that this no longer the problem it once was.

Not true, I shoot a lot with the NEX series cameras and it is still an issue on the last year's models of the NEX 3 and 5. Certain Leica mount rangefinder lenses have poor corner performance and color shifts towards the corners, mainly wide angle lenses.

However, the NEX 5n, and presumably the 7 fix the color shift problem by using appropriate microlenses. The NEX system has the shortest register distance of the large sensor mirrorless cameras, so it will likely be hit the hardest by this, and since it is visible on APS-C sensor in the NEX, it would be that much more difficult to correct on a full frame mirrorless camera, but they should be able to (even if it resorts to software correction like Olympus/Panasonic use).

You are correct that color shifts are pretty much a non issue for SLR registration distances, where wide angles are retrofocus anyway so the light doesn't strike the sensor at much of an angle. The color shift is only an issue for true wide angle lenses on a mirrorless system, where the light at the corners hits at a much steeper angle.

Eric

--
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be what it may - light, shade, and perspective will always make it
beautiful. - John Constable (quote)

See my Blog at: http://www.erphotoreview.com/ (bi-weekly)
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[Alex Sarbu]

The proliferation of mirrorless cameras with very short register distances stands as evidence that this no longer the problem it once was.

Not true, I shoot a lot with the NEX series cameras and it is still an issue on the last year's models of the NEX 3 and 5. Certain Leica mount rangefinder lenses have poor corner performance and color shifts towards the corners, mainly wide angle lenses.

I find it interesting that Olympus was talking big time about telecentric lens designs when they launched the 4/3 DSLR system; how important it is, and how other (makers) lenses aren't good enough. With m4/3, suddenly there is no need for this telecentric design

Alex S

 

[miles green]

Indeed, a very interesting perspective!

Another problem with FF would be integrating SR. Would the camera want to compensate for user shake by shifting the sensor.. outside the lens' image circle?

The bad symptoms on digital cameras are mainly caused by wide angles, especially those for rangefinders that have lens elements very close to the film/sensor plane. Leica is very affected my this and have used both software and hardware solution to tame the problem. All their new wide-andle lens are now retrofocus lens, so are dslr wides. They keep the back of the lens much further away from the film plane, a smaller incidence angle decreasing fall-off especially on digital. These lens are much bigger than their short-focus symmetrical predecessors. This, and coated rear elements, is the main difference btween film and digital lens.

Software solutions include "Cornerfix" and "Vignette" for Leica M and Sigma DP users. You can of course do it with photoshop & the like as well, provided you have enough DR in the first place.

I still want a FF!

Very interesting perspective. How do modern FF lenses deal with this problem, the angles and sensor surface are the same for both new and old FF lenses, what is the modification that makes modern FF lenses better? Is it just the coating to reduce reflections from the back even more, or they reduce the angles by making the lens physically longer for the given focal length?

--
-----------------------------------------------
Miles Green
Corfu

 

[DS21]

I still want a FF!

Me too, I would be willing to tolerate the faults of old FF lenses in corners, for the added creative benefit of shallower DOF. And my vintage zooms starting at 28mm would become much more interesting. I would still keep one APS-C Pentax at hand anyway.

 

[zakaria]

Pentax has been making cameras since 1919 and in 1952 Pentax made the first SLR camera! In 1971 Pentax came out with the first multi-coated lens; its now famous SMC (Super Multi Coat). Around 1975 Pentax came out with the K mount. Since that time until pentax stopped making film SLRs Pentax produced millions and millions of lens that are in peoples homes around the world.

Pentax kept its old K mount that let everyone use all those millions of lens just sitting around. Moreover they made those old lens easy to use with the “Green Button”. What this button did was meter for you even in manual mode!

Full frame is a bigger size than APS, and some photographers want Pentax to make full frame dSLRs again just as Canon and Nikon are making today. They feel Pentax is missing the boat or that it will make a more complete system. One reason is all of those millions of lens were designed for 35mm or full frame size film. So naturally why not make a full size sensor? Why does Pentax hold on to APS only for SLRs as of today?

Maybe this is one of the reasons -

It could be that 10 years ago Pentax tested and found what Klaus, owner (and tester) of the lens testing site Photozone found. Many, a good percentage of older film lens don’t work well with full frame sensors. The reason is film was forgiving of the angle light was hitting it (see examples below) film is a thick media compared to digital sensors. To help visualize the difference think of film as a piece of paper and a pixel of a sensor as a piece of paper down in a cup 3” round and a three inches deep with the paper at the bottom. Now imagine the light source a ceiling lamp but you your cup and paper are in the corner of the room. Which paper would receive the most light? Of course it would be the paper out in the open. Scientist have made bubble type lens that sit on top of the cup to help capture the light at the edges and corners but it still falls well short of film and there is a light loss.

Now what’s a good way to make all those millions of lens perform well in a digital sensor? Make a smaller room (in the analogy above) so the light hits the cup at less of an angle. And that’s what Pentax has been doing by staying with APS sensors that are 1.5X smaller than FF. It allows the best performance out of those older lens that are not made for the extreme demands of digital sensors. There is more to the benefits. Even if light did strike a FF digital sensor perfect, cropping out the edges leaves the best image quality produced from lens. That’s in the center then boarders, corner are worse but are cropped out with APS sensors. So it’s a double benefit by using APS sensors with older full frame lens. You eliminate the light loss in the corners and crop out the worse part of a lens image quality. For telephoto fans you also make it 1.5X longer e.g. 50mm is 75mm, but wide angle fans lose 1.5x!

--
jamesm007,

a very very interesting perspective..even though nikon went with full fram system and it has milions film lenses around the world. nikon began with a 2 digital ff lenses 24-70 &70-200 then 14-24.

I think pentax always thinks twice before trying any thing new. it did that when it decided to go with digital.

--
my PPG
http://www.pentaxphotogallery.com/zakariamohie
Nikon shooter in love with Pentax

 

[jamesm007]

This was an issue in the early days of digital sensors, but technology has moved on. Sensors that must deal with light striking the sensor at low angles of incidence now use microlenses positioned just above the pixels to direct light down into the pixel wells.

The proliferation of mirrorless cameras with very short register distances stands as evidence that this no longer the problem it once was.

I very well know that. Samsung was the first in the K20D to use short wells and gap-less micro-lens over the well. Here is a quote from the K20D image quality page -

"The K20D’s new CMOS image sensor is designed to receive the incoming light at optimum efficiency and accuracy even with these film-format lenses."

Pentax has always worked on making older film lens as good as can be.

--
jamesm007,

http://www.flickr.com/photos/jamesm007/
http://s195.photobucket.com/albums/z77/jamesm700/

 

[Zvonimir Tosic]

And Leica have arranged for a sensor that minimises all the problems inherent with digital sensors + old lenses.

And, now, just look at that: Leica has made an FF camera that sells like hotcakes! They can't make enough of them! So what's the real problem here?

Any argument presented by dr Klaus, mrs Mom, army of Pentax fans, etc. trying to rationalise something that cannot be rationalised (APS-C only design) makes no sense.

An FF digital Nikon has virtually resurrected the Nikon company from shambles and in a few years it has regained MUCH of its user-base. Pentax never did.

Pentax did not do it because a) it was already late to digital game, b) did not have enough $$, c) was looking for investors, d) investor Hoya couldn't care less.

It was a wrong business decision, one that cannot be hidden behind the weak technology reason. By pure luck and also by ingenious design of their APS-C cameras they have managed to create a loyal user-base.

To keep them all under the same flag, they do need an FF — badly — and they do need to spend some quality time to design those offset micro-lenses and polish the software within the FF camera to make those FF sensors work perfectly with old glass.

--
Zvonimir Tosic

 

[jamesm007]

Very interesting perspective. How do modern FF lenses deal with this problem, the angles and sensor surface are the same for both new and old FF lenses, what is the modification that makes modern FF lenses better? Is it just the coating to reduce reflections from the back even more, or they reduce the angles by making the lens physically longer for the given focal length?

The rear lens, or field elements is designed to send light more perpendicular to the sensor. Before, with film, this was not a factor. So there is room to guide the light better, and really the whole lens is designed for digital.

Some lens such as the DA18-55mm WR is designed from the ground up for digital. You must fully understand digital sensors are 100% completely different that film and have much higher requirements from the lens. But lucky for use lens now use much more ED and Aspherical elements! Its a must in digital lens.

--
jamesm007,

http://www.flickr.com/photos/jamesm007/
http://s195.photobucket.com/albums/z77/jamesm700/

 

[jamesm007]

The proliferation of mirrorless cameras with very short register distances stands as evidence that this no longer the problem it once was.

Not true, I shoot a lot with the NEX series cameras and it is still an issue on the last year's models of the NEX 3 and 5. Certain Leica mount rangefinder lenses have poor corner performance and color shifts towards the corners, mainly wide angle lenses.

I find it interesting that Olympus was talking big time about telecentric lens designs when they launched the 4/3 DSLR system; how important it is, and how other (makers) lenses aren't good enough. With m4/3, suddenly there is no need for this telecentric design

Alex S

This has nothing to do with using an older film lens on a newer full frame digital sensor!

Read the reviews at Photozone! Research the subject.

No one is going to tell you and lose a sale
--
jamesm007,

http://www.flickr.com/photos/jamesm007/
http://s195.photobucket.com/albums/z77/jamesm700/

 

[jamesm007]

OK how about a modern Nikon 3DX FX with a 1990s film lens. SLRgear also has examples if you want to look. But I have seen enough through my research to know overall film lens on FF digital sensors will never perform as well as on a APS sensor. Moreover the lens may even have aberrations such that it makes little sense to buy it versus a more modern lens (on FF).

http://www.photozone.de/nikon_ff/617-nikkorafd2028ff

Also I don't like micro-lens. Naturally all microlens have aberrations that needs to be addressed in the camera. There are no free lunches. The best compromise IMO for old (1970s, 1980s...) film lens is the APS sensor. Yes even my old K20D has micro-lens. It also features a short well to let in more light. The problem just increases is all I am saying the bigger the sensor gets. Its not a major problem, but if your going to market you whole dSLR tied to film lens best to use APS sensor and shake reduction. This made Pentax standout at first.

Its worked great for Pentax really. How many would have gone Pentax if they could not have used their old lens?
--
jamesm007,

http://www.flickr.com/photos/jamesm007/
http://s195.photobucket.com/albums/z77/jamesm700/

 

[moving_comfort]

OK how about a modern Nikon 3DX FX with a 1990s film lens. SLRgear also has examples if you want to look. But I have seen enough through my research to know overall film lens on FF digital sensors will never perform as well as on a APS sensor. Moreover the lens may even have aberrations such that it makes little sense to buy it versus a more modern lens (on FF).

http://www.photozone.de/nikon_ff/617-nikkorafd2028ff

.

I don't think that's a good example of a lens that proves your point, though.

The 20 f/2.8D is sought after by FF shooters because it's very sharp in the center wide-open and very, very small. In fact the 'flaws' of this lens (some vignetting on FF, some distortion, some CA) are more attributable to it's size more than anything else. When you make a very small 20mm f/2.8 lens, some sacrifices get made.

I love the 20mm f/2.8D on FF and it goes with me a lot of places.

.

--
Here are a few of my favorite things...
---> http://www.flickr.com/photos/95095968@N00/sets/72157626171532197/

 

[jamesm007]

OK how about a modern Nikon 3DX FX with a 1990s film lens. SLRgear also has examples if you want to look. But I have seen enough through my research to know overall film lens on FF digital sensors will never perform as well as on a APS sensor. Moreover the lens may even have aberrations such that it makes little sense to buy it versus a more modern lens (on FF).

http://www.photozone.de/nikon_ff/617-nikkorafd2028ff

.

I don't think that's a good example of a lens that proves your point, though.

The 20 f/2.8D is sought after by FF shooters because it's very sharp in the center wide-open and very, very small. In fact the 'flaws' of this lens (some vignetting on FF, some distortion, some CA) are more attributable to it's size more than anything else. When you make a very small 20mm f/2.8 lens, some sacrifices get made.

I love the 20mm f/2.8D on FF and it goes with me a lot of places.

.

--
Here are a few of my favorite things...
---> http://www.flickr.com/photos/95095968@N00/sets/72157626171532197/

Whoops, well not that lens but some others.

--
jamesm007,

http://www.flickr.com/photos/jamesm007/
http://s195.photobucket.com/albums/z77/jamesm700/

 

[ernieF]

I used Olympus 4/3 from E-1 through E-3, and a primary reason was the quality of those telecentric lenses. And early on Olympus really did promote their "telecentric lens" concept heavily. I guess they were right at the time as the 14-54, 50-200, 11-22 lenses etc were/are excellent-- still.

But Olympus made two critical (and strategic) errors in judgement IMO, and they were simply that sensor design was going to remain constant (CCD) and of course that the 4/3 sensor was simply smaller and less IQ competitive.

Hind sight is 20/20 though and of course sensor designs have essentially eliminated the need for "telecentricity". When was the last time anyone saw an Olympus ad promoting telecentric lenses?-- and especially since they created micro 4/3 (with good success I think) and dramatically shortened lens/sensor registration distance.

I went through Canon and have happily ended up w/ Pentax K5s and a gaggle of Pentax glass-- happy as "clams in mud" too;> ). I don't need/want FF, but would like to see it for those that do. Though I want a good DA 400mm f5.6 first;> )

Cheers. ernie

 

[jamesm007]

I used Olympus 4/3 from E-1 through E-3, and a primary reason was the quality of those telecentric lenses. And early on Olympus really did promote their "telecentric lens" concept heavily. I guess they were right at the time as the 14-54, 50-200, 11-22 lenses etc were/are excellent-- still.

But Olympus made two critical (and strategic) errors in judgement IMO, and they were simply that sensor design was going to remain constant (CCD) and of course that the 4/3 sensor was simply smaller and less IQ competitive.

Hind sight is 20/20 though and of course sensor designs have essentially eliminated the need for "telecentricity". When was the last time anyone saw an Olympus ad promoting telecentric lenses?-- and especially since they created micro 4/3 (with good success I think) and dramatically shortened lens/sensor registration distance.

I went through Canon and have happily ended up w/ Pentax K5s and a gaggle of Pentax glass-- happy as "clams in mud" too;> ). I don't need/want FF, but would like to see it for those that do. Though I want a good DA 400mm f5.6 first;> )

Cheers. ernie

Take a read this is 2010 and 2011

http://www.luminous-landscape.com/essays/an_open_letter_to_the_major_camera_manufacturers.shtml

Below is a quote from the links article.

"The DxO measurements to date prove that the marginal light rays just don’t hit the sensor.."

Does anyone have hard core scientific data to back statements of "its not a problem anymore". What breakthrough made it not a problem?

From DxO "We can suspect,” Guichard continued, “that sensors collect the incoming light all the more improperly, in that this light comes from a more oblique angle. Since faster lens have, by definition, a wider opening, they raise the proportion of oblique light, hence the proportion of lost energy which never lands on the pixels.”

http://www.dxomark.com/index.php/Publications/DxOMark-Insights/F-stop-blues

From Mark Dubovoy of Luminous Landscape Link given above.

When you look at the structure of CMOS sensors, each pixel as basically a tube with the sensing element at the bottom. If a light ray that is not parallel to the tube hits the photo site, chances are the light ray will not get to the bottom of the tube and will not hit the sensing element. Therefore, the light coming from that light ray will be lost. It appears from this graph that when using large aperture lenses on Canon cameras, there is a substantial amount of light loss at the sensor due to this effect. In other words, the "marginal" light rays coming in at a large angle from near the edges of the large aperture are completely lost.

By the way, this type of light loss is the main reason that modern lenses designed for digital photography place great emphasis on the direction of light rays behind the lens. It is also an important reason why Medium Format backs (often used with camera movements such as tilt, rise/fall and shift) and the Leica M9 (with lenses that produce mostly oblique light rays) use CCD sensors with a very different structure, rather than CMOS sensors.

Another quote from DxO and this is up to date material written Nov 2010.

"Loss of light at wider aperture

“We have been very surprised,” explained Frédéric Guichard, chief scientist at DxO Labs, “to find out that some of the gain from wider lens openings seems to be offset by the present state of sensor technology. Our measurements all point in the same direction: as you go further than f/ 4 – to f 2 and wider, the accrued quantity of light falls marginally onto the sensor. A stronger and stronger part of this additional light is blocked or lost. I am therefore inclined to question the real benefit of faster lenses.”

This loss seems to increase when the pixel size decreases, as shown on the figure below

-
jamesm007,

http://www.flickr.com/photos/jamesm007/
http://s195.photobucket.com/albums/z77/jamesm700/

 

[Cideway]

Hind sight is 20/20 though and of course sensor designs have essentially eliminated the need for "telecentricity". When was the last time anyone saw an Olympus ad promoting telecentric lenses?-- and especially since they created micro 4/3 (with good success I think) and dramatically shortened lens/sensor registration distance.

The most likely reason for Olympus not promoting their telecentric lenses is that it is no longer the USP, as all the manufacturers are now making telecentric lenses. At the time when Oly were really pushing it all the other lens makers were mostly using legacy film designs or hastily pushed out designs.
--
Chris.

A weather sealed ultra wide, is that too much to ask?

http://www.pentaxphotogallery.com/chriside

GMT +9.5

Pentax SLR talk FAQ
http://forums.dpreview.com/forums/read.asp?forum=1036&message=23161072

 

[Cideway]

Pull your head out of that place you put it, the FX format had nothign to do with Nikon's resurgence, they would have sold and by a very large margin more D300's, then the D3(s,x) and D700 combined.

Their resurgence was because the release several very good products and several cheap camera bodies at a time when their competitor (Canon) was releasing crap.
--
Chris.

A weather sealed ultra wide, is that too much to ask?

http://www.pentaxphotogallery.com/chriside

GMT +9.5

Pentax SLR talk FAQ
http://forums.dpreview.com/forums/read.asp?forum=1036&message=23161072