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06-06-2011, 10:32 AM   #46
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QuoteOriginally posted by bdery Quote
Now your talking again of marketing strategies, and apparently expressing disappointment with Pentax. We're not talking about lens design anymore, but about market development strategies.
OK. Talk lens designs.

Why is Pentax no longer able to produce F/1.2 or F/1.4 glass? Can they not produce a DA* 85mm f/1.4 for less than $2,000? How about a DA* 135mm f/1.8?

What is preventing Pentax from producing high quality fast glass? Other companies apparently don't have the same problems with it.

06-06-2011, 10:47 AM   #47
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Are fast lenses less efficent when used with sensors?

I remember a thread from a few months back to the effect that the light from faster lenses does not strike the sensor in a perpendicular manner near the edges, and therefore fast lenses are not as efficient as they were when used with film.

The outrage in the thread was over camera makers programming the body circuits to up the ISO whenever fast lenses were installed to make up for this sensor weakness in using all the light from a fast lens.

There was a lot of volatile posts on this issue, then it died away, and again we have threads asking for faster Pentax lenses.

If all the manufacturers are doing is upping the ISO when a fast lens is installed, - geez, i can up the ISO with any lens installed.

So was this thread from a few months back correct or partially correct about the lack of optical efficiency with fast lenses? Hope i've said this well enough to get the point across.
06-06-2011, 10:58 AM   #48
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QuoteOriginally posted by philbaum Quote
I remember a thread from a few months back to the effect that the light from faster lenses does not strike the sensor in a perpendicular manner near the edges, and therefore fast lenses are not as efficient as they were when used with film.

The outrage in the thread was over camera makers programming the body circuits to up the ISO whenever fast lenses were installed to make up for this sensor weakness in using all the light from a fast lens.

There was a lot of volatile posts on this issue, then it died away, and again we have threads asking for faster Pentax lenses.

If all the manufacturers are doing is upping the ISO when a fast lens is installed, - geez, i can up the ISO with any lens installed.

So was this thread from a few months back correct or partially correct about the lack of optical efficiency with fast lenses? Hope i've said this well enough to get the point across.
This is true, but you have to think about how most fast glass is used. To use the 85L as an example it is primarily a portrait lens where the DoF is so narrow that the edges will be OOF anyway. Macro & landscape people need edge to edge sharpness and a lot of DoF, so they don't need fast glass.

Telecentric lens designs solve most of the problems associated with faster apertures, but they are big and expensive to produce compared to standard lens designs.
06-06-2011, 11:00 AM   #49
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QuoteOriginally posted by Winder Quote
OK. Talk lens designs.

Why is Pentax no longer able to produce F/1.2 or F/1.4 glass? Can they not produce a DA* 85mm f/1.4 for less than $2,000? How about a DA* 135mm f/1.8?

What is preventing Pentax from producing high quality fast glass? Other companies apparently don't have the same problems with it.
I think they're *able* to; they just choose not to, for whatever marketing reasons they have come up with. They make the DA* 55 f1.4. I couldn't begin to guess why they *choose* not to make faster glass, but I doubt it's about their ability to do so.

06-06-2011, 11:19 AM   #50
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QuoteOriginally posted by jstevewhite Quote
I think they're *able* to; they just choose not to, for whatever marketing reasons they have come up with. They make the DA* 55 f1.4. I couldn't begin to guess why they *choose* not to make faster glass, but I doubt it's about their ability to do so.
I agree. People seem to be implying that it is too difficult to make high quality fast glass. That is why I made the statement.
06-06-2011, 11:23 AM   #51
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QuoteOriginally posted by philbaum Quote
I remember a thread from a few months back to the effect that the light from faster lenses does not strike the sensor in a perpendicular manner near the edges, and therefore fast lenses are not as efficient as they were when used with film.

The outrage in the thread was over camera makers programming the body circuits to up the ISO whenever fast lenses were installed to make up for this sensor weakness in using all the light from a fast lens.

There was a lot of volatile posts on this issue, then it died away, and again we have threads asking for faster Pentax lenses.

If all the manufacturers are doing is upping the ISO when a fast lens is installed, - geez, i can up the ISO with any lens installed.

So was this thread from a few months back correct or partially correct about the lack of optical efficiency with fast lenses? Hope i've said this well enough to get the point across.
I think you nailed it. I know little about the subject on a technical level, but my *guess* is that Pentax is dealing with a very low number of customers interested in such fast glass, so they produce a few lenses capable of this performance for the die hards, and focus on the f2.8 range for those of us who are not DOF obsessed. The rendering of fast glass is unmistakable, but important to only a small segment of the camera buying community.

It makes sense, because they can keep costs to the consumer down, while keeping profits about the same for them. The pentax market is pretty cost-conscious, so this strategy seems sound.

HEY - I just realized something. My K55 1.8 underexposes about 1 stop when wide open w/ green button metering. Do you think this could be because it does not transmit aperture information, and therefore the camera meters without any of these ISO adjustments?
06-06-2011, 11:42 AM   #52
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QuoteOriginally posted by paperbag846 Quote
I think you nailed it. I know little about the subject on a technical level, but my *guess* is that Pentax is dealing with a very low number of customers interested in such fast glass, so they produce a few lenses capable of this performance for the die hards, and focus on the f2.8 range for those of us who are not DOF obsessed. The rendering of fast glass is unmistakable, but important to only a small segment of the camera buying community.

It makes sense, because they can keep costs to the consumer down, while keeping profits about the same for them. The pentax market is pretty cost-conscious, so this strategy seems sound.
The 31mm LTD is a specialty lens that is very expensive. Pentax makes limited production runs of the 31mm, 43mm, & 77mm. They make even more limited production runs of Silver versions. If Pentax can be profitable making these lenses in such small numbers then they can do the same with other focal lengths. I think lenses like the 31mm show that Pentax users will pay for high quality glass.
06-06-2011, 11:48 AM   #53
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QuoteOriginally posted by paperbag846 Quote
I think you nailed it. I know little about the subject on a technical level, but my *guess* is that Pentax is dealing with a very low number of customers interested in such fast glass, so they produce a few lenses capable of this performance for the die hards, and focus on the f2.8 range for those of us who are not DOF obsessed. The rendering of fast glass is unmistakable, but important to only a small segment of the camera buying community.

It makes sense, because they can keep costs to the consumer down, while keeping profits about the same for them. The pentax market is pretty cost-conscious, so this strategy seems sound.

HEY - I just realized something. My K55 1.8 underexposes about 1 stop when wide open w/ green button metering. Do you think this could be because it does not transmit aperture information, and therefore the camera meters without any of these ISO adjustments?
My Helios 44M (58 f2) does not underexpose at all. I would have guessed that it was a progressive situation - that is, gradually scaling up in underexposure.

This whole idea makes *zero* sense to me. If I put a FF lens - say, a 50mm f1.2 - on my K-5, the amount of light hitting the sensor is *exactly the same as if it were a FF sensor, CROPPED to 16x24mm*. By any measure I can think of, it should be the same amount of light that would hit the film plane in a film camera. I can't think of any reason that would make its performance different from a FF. Now, there might be something related to the AA filter and incidence angle, but that would be the case on a FF digital camera as well (the angle, again, would be the same). Why would we need to up the ISO?

EDIT: Oh, I see - he did say "as they were with film". That makes more sense. But why don't we see heavy vignetting when we use wide angles due to the high angle of incidence?

06-06-2011, 05:00 PM   #54
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QuoteOriginally posted by newarts Quote
Doesn't the short registry distance give rise to image circle problems? I guess the answer is likely no for long focal lengths but why then does the shorter registry distance matter?
not really, Kodak has developed offset microlenses to compensate for that - and I have been using my Leica M9 for some time and even with ultra fast lenses like the Noctilux 50mm f0.95 ASPH vignetting is very well controlled. The only reason leica M cameras are essentially limited to 135mm as their longest current focal length is the rangefinder baselength isn't long enough.
06-06-2011, 06:53 PM   #55
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When I look at the recient responses, there are some truths, half truths, and complete myths.

Yes, there is some issue, especially with the earliest sensors and vignetting, with non "digital" lenses, and as digitalis says, kodak made offset lenses for the Leica camera, but the problem is far exagerated there due to the much shorter register distance of the leica camera. I believe leica also has radially modified the ISO to help on vignetting as well, therefore, the measured linearity center to edge is good.

there are other issues on fast glass, such as the need to make aprocrhomatic front elements or do in camera correction for lateral CA, both of which are harder to control with very fast lenses.

As for low level of interest, I don't buy that, I think there is sufficient interest based upon the number of shooters who are going elsewhere and back into legacy lenses, just to get fast lenses.

BUT, look up an old film lens report on fast 50mm lenses, where it reports vignetting is gone by F2.8 to F3.5 on the K 50/1.4 for example. I looked at the performance of my K50/1.4 and it is -3/4 of a stop at the corner wide open and perfect by F2. Now that is on a cropped sensor, but it is consistent with the origonal film reports so for me vignetting is a myth.

As for lenses not being as fast as reported, tall manufacturers cheat on this, and use the limits of the standards for lenses to make thier claims, that is just thenature of specmanship.

As for the question of the wide angle lenses and vignetting, the answer is really simple. Most wide angle lenses use a design where the last group still provides magnification and when you look at the regester distance of the lens, and the location of the rear element, there is no difference in distance from the rear element to the sensor on my sigma 10-20, my samyang 14, or my SMC 50/1.4 since the light has to spread out the same amount from each of these lenses to the corners of the frame/sensor, why would one focal length vignette more than another. all these lenses would have the same angle at the corners, of light hitting the sensor.

I did some tests
06-07-2011, 01:17 AM   #56
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QuoteOriginally posted by Lowell Goudge Quote
for lenses not being as fast as reported, all manufacturers cheat on this, and use the limits of the standards for lenses to make their claims, that is just the nature of specmanship.
very true, Minolta (Sony) are the biggest culprit for this. The Rokkor 50mm f/1.7 was only transmitting 83% of the light while the Pentax 50mm f/1.7 - (a contemporary lens design) was transmitting close to 94% - these difference in transmission can be chalked up to the coatings used on the lenses.

QuoteOriginally posted by Lowell Goudge Quote
problem is far exagerated there due to the much shorter register distance of the leica camera. I believe leica also has radially modified the ISO to help on vignetting as well, therefore, the measured linearity center to edge is good.
from what I have seen the vignetting from the lenses is pretty consistent from the summilux 21mm f/1.4 to the 'lux 75mm f/1.4 which can be because of either the microlenses, or behind the scenes ISO bumping. The leica M9 has arguable the worst High ISO performance from a FF sensor I have worked with (my nikon D3s is the current High ISO prize winner for me) and if Leica was bumping the ISO values it would be pretty obvious - though I haven't checked my M9 for this...I'll get back to you on that.
06-07-2011, 05:06 AM   #57
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QuoteOriginally posted by Winder Quote
Why is Pentax no longer able to produce F/1.2 or F/1.4 glass?
They choose not to, but they certianly can.

QuoteOriginally posted by Winder Quote
What is preventing Pentax from producing high quality fast glass?
You'd have to ask them... that's marketing again.

QuoteOriginally posted by philbaum Quote
I remember a thread from a few months back to the effect that the light from faster lenses does not strike the sensor in a perpendicular manner near the edges, and therefore fast lenses are not as efficient as they were when used with film.
It's true that all things being equal a telecentric lens will be better with digital sensors. It,s also true that it particularly applies to fast, long glass. But we've seen countless examples showing that older glass still performs well on digital. I believe that older lenses on full frame digital sensors would be worse, however.

QuoteOriginally posted by paperbag846 Quote
my *guess* is that Pentax is dealing with a very low number of customers interested in such fast glass, so they produce a few lenses capable of this performance for the die hards, and focus on the f2.8 range for those of us who are not DOF obsessed. The rendering of fast glass is unmistakable, but important to only a small segment of the camera buying community.
That's quite probably true.

QuoteOriginally posted by Lowell Goudge Quote
As for low level of interest, I don't buy that, I think there is sufficient interest based upon the number of shooters who are going elsewhere and back into legacy lenses, just to get fast lenses.
I have to suggest that we can either

-believe all decision makers at Pentax are fools, or

-they know what they are doing, and have more information than any of us (all we have regarding marketing is speculation)

Pentax is profitable, growing, and constantly improving their products. I'd trust them to know how to keep making profits. I'm not working in photography, but in a large photonics company, and I can attest that here, at least, the marketing guys are very much aware of where their market is going, and how to turn a profit.
06-07-2011, 06:41 AM   #58
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QuoteOriginally posted by bdery Quote
I believe that older lenses on full frame digital sensors would be worse
not entirely true, I have seen canon and nikon photographers using M42 takumar lenses from the '60s on their cameras and they produce impressive results
06-07-2011, 07:09 AM   #59
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QuoteOriginally posted by Digitalis Quote
I think you are forgetting that they are still using exactly the same lens mount and flange distance as they have been using for to past 50+ years. The reason why Leica M cameras are able to have such fast lenses designed for them is because their short flange distance - which is 27.80mm the pentax flange is 45.46mm - almost twice that of the leica.
Yes, but Nikon's is only slightly different than the Pentax mount dimensions so looking at the fast glass in the Nikon catalog both present and past should give a rough idea of the possibilities. Cost is a separate issue.
06-07-2011, 07:10 AM   #60
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QuoteOriginally posted by Digitalis Quote
not entirely true, I have seen canon and nikon photographers using M42 takumar lenses from the '60s on their cameras and they produce impressive results
There have been several A and K 50mm 1.2 lenses show up with the aperture lever cut off to clear the mirror on those damn full frame canon bodies.
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