[aslyfox]

Tested by Pentax during the design process of the lens. I love my FA 77mm and FA 31mm...but I think of them as lenses that create unique rendering rather than some number on a test chart, which is what Pentax designed them for.

and those of us who own them appreciate the difference

[bdery]

Digital sensors have micro lenses that gather light at oblique angles. Film lenses are not optimized for these micro lenses means that there is a loss of resolution and vignetting.

Yes and no. In fact the photosensitive particles on film are able to gather light from many directions, that's true. And microlenses are trying to emulate this (and mitigate the fact that CMOS sensors have non-light sensitive components at the surface). Without saying they're equal, they're actually pertty close, and certainly closer than what they were before they used microlenses.

I've never seen any quantifiable data suggesting film and digital sensors have to be different.

They don't have to, regarding angles. They certainly are, regarding wavelengths.

The common practice of releasingf specs based on analysis of the design by a computers certainly would suggest not. It would suggest they aren't even doing testing on the actual product, but using numbers of un-known reliability.

I've never worked on a photo lens design lab, but I'm an optical designer. You are correct that designs are done via a computer. These designs, when well made, take into account flaws in materials, manufacturing tolerances, and many other elements most users would never even think about. THEN they are (or should be) tested via prototyping, "beta" iterations, pre-production samples, and performances qualification.

"Numbers of unknown reliability" is an expression which makes no sense to me, especially in this context.

That being said, those of us who use film area lenses have to be sensitive to conditions that might cause purple fringing, which apparently was not an issue on film.

All of my film era lenses purple fringe more than my more modern designs.

Digital sensors are more sensitive to UV light than film. That's why PF shows often with older lenses. PF is in fact a manifestation of CA, but for wavelengths that our eyes (and film) don't see while the sensor does. It should be filtered out before reaching the sensor, but that's not always the case. I suspect most recent camera designers stopped caring bout it because the lens designs nowadays take care of it. With older lenses, that's not the case, but camera manufacturers want you to purchase new lenses, so there's no incentive for them to optimize for old glass.

My SMC Pentax-FA 77mm F1.8 arrived today

Your latest acquisition - PentaxForums.com

where are the cookies ?

This is what I could gather on short notice. I might be able to do better over the weekend

[microlight]

‘Making pictures’ is a very good way of describing it; that’s what Limiteds do so well.

[beachgardener]

cookies, here we call them biscuits

[Des]

"Lenses for the way people take pictures, not for the test charts."A concept every other Camera company and their followers (and it sounds like half of Pentax) couldn't wrap their head's around. It is still being manufactured by the same archaic process used to achieve that effect, yet here we are 20 years later, still in production. Sometimes everyone else is in error, those who think different are right. It happens.

You are correct that designs are done via a computer. These designs, when well made, take into account flaws in materials, manufacturing tolerances, and many other elements most users would never even think about. THEN they are (or should be) tested via prototyping, "beta" iterations, pre-production samples, and performances qualification.

If a company now were to be crazy-brave enough to design a lens, for digital cameras, based on a similar aesthetic to the FA Ltds, could it be done? How?

With the FA Limiteds, the designers worked backwards from the output medium on which the image was to be viewed - a high-quality print - and refined their prototypes using that reference point. With digital images, the output medium is quite variable. (Not to mention the variables based on the camera/sensor used.) Would that be a significant limitation? (That is, of course, apart from all the other limitations, like cost, a shrinking market, nervous sales departments and fear of bad reviews based on test charts, to mention a few.)

[ashurbanipal]

Very interesting information here.

[Mikesul]

Yes and no. In fact the photosensitive particles on film are able to gather light from many directions, that's true. And microlenses are trying to emulate this (and mitigate the fact that CMOS sensors have non-light sensitive components at the surface). Without saying they're equal, they're actually pertty close, and certainly closer than what they were before they used microlenses.



They don't have to, regarding angles. They certainly are, regarding wavelengths.



I've never worked on a photo lens design lab, but I'm an optical designer. You are correct that designs are done via a computer. These designs, when well made, take into account flaws in materials, manufacturing tolerances, and many other elements most users would never even think about. THEN they are (or should be) tested via prototyping, "beta" iterations, pre-production samples, and performances qualification.

"Numbers of unknown reliability" is an expression which makes no sense to me, especially in this context.



Digital sensors are more sensitive to UV light than film. That's why PF shows often with older lenses. PF is in fact a manifestation of CA, but for wavelengths that our eyes (and film) don't see while the sensor does. It should be filtered out before reaching the sensor, but that's not always the case. I suspect most recent camera designers stopped caring bout it because the lens designs nowadays take care of it. With older lenses, that's not the case, but camera manufacturers want you to purchase new lenses, so there's no incentive for them to optimize for old glass.



This is what I could gather on short notice. I might be able to do better over the weekend

Naive user question. Many of us used to use UV filters with film but stopped with digital because it was said they were useless with digital. Would use of UV filters help with CA?

[aslyfox]

Naive user question. Many of us used to use UV filters with film but stopped with digital because it was said they were useless with digital. Would use of UV filters help with CA?

As I understand it, the digital camera bodies are what make some folks recommend no need for use of filters

Not the lens used

[dcpropilot]

Very interesting....I thought knew some of this already, but really great being able to gain more perspective on the behind the scenes on how it all came together, as well as what to expect from the limiteds and the philosophy that went into them (when shooting with them). And the secret close focus function of the 77.

[Mikesul]

As I understand it, the digital camera bodies are what make some folks recommend no need for use of filters

Not the lens used

Read the post quoted. The old lenses seem to have CA because they do not correct for UV as modern lenses do. Digital sensors are more sensitive to UV than film. Hence maybe a UV filter would help.

[bdery]

If a company now were to be crazy-brave enough to design a lens, for digital cameras, based on a similar aesthetic to the FA Ltds, could it be done? How?

It could be done by following the same method that was used for the FA Limiteds.

Modern mediums are variable (screens technology, size and resolution, etc), but the same was true in the film era. The type of film used had a great influence on the output.

Naive user question. Many of us used to use UV filters with film but stopped with digital because it was said they were useless with digital. Would use of UV filters help with CA?

With CA, no. With PF, to some extent yes but it would depend on the specific wavelengths blocked by the UV filter. Photographers are not equipped to properly test this, you would need a spectrometer. I suspect (but have never verified) that most UV filters are in fact mostly good at transmitting visible light, and not particularly good at blocking UV light. Also, it depends which wavelengths the lens is "weak" at handling. UV light is a broad spectrum, just as visible light is. So it depends on which wavelengths the camera and sensor are sensitive to, which wavelengths are not blocked by the UV filter, and which wavelengths are poorly handled by the lens.

[aslyfox]

Read the post quoted. The old lenses seem to have CA because they do not correct for UV as modern lenses do. Digital sensors are more sensitive to UV than film. Hence maybe a UV filter would help.

as I said, I thought the digital camera bodies adjusted for UV

I have never claimed to be an expert however

perhaps I should have said they are not as sensitive to UV ??

the following all discuss " sensors " which is part of the digital camera

thus my thought that the type of lens doesn't matter

The thing is, modern films and digital sensors just aren’t sensitive to UV light. It doesn’t affect them the way it does older films. This means you don’t need a UV filter to block UV light in order to take good photos. However, this hasn’t stopped UV filters from picking up a secondary use as a protective filter for your lenses. Some camera shops are reluctant to let you walk out the door with a new lens, if you haven’t also bought a UV filter to protect it.

What is a UV Filter and Do You Need it to Protect Your Camera Lens?

_________________

HAZE & UV FILTERS
Nowadays UV filters are primarily used to protect the front element of a camera lens since they are clear and do not noticably affect the image. With film cameras, UV filters reduce haze and improve contrast by minimizing the amount of ultraviolet (UV) light that reaches the film. The problem with UV light is that it is not visible to the human eye, but is often uniformly distributed on a hazy day; UV therefore adversely affects the camera's exposure by reducing contrast. Fortunately, digital camera sensors are nowhere near as sensitive to UV light as film, therefore UV filtration is no longer necessary.

- Choosing a Camera Lens Filter

___________________

There’s some debate among photographers about whether UV filters are useful for modern digital cameras. They were necessary for film cameras because film is very sensitive to UV light. But digital sensors are less sensitive.

However, UV filters can still remove UV haze in specific situations. For that reason, they are sometimes referred to as haze filters.

Digital cameras will only pick up this type of haze when ambient UV levels are very high. One example would be if you were shooting at a high elevation on a bright day and near large reflective surfaces like snow or a body of water. In that situation, if you tried shooting a distant subject, the UV light between the subject and your camera could result in haze in your image. A UV filter would remove that haze.

It’s important to keep in mind that UV filters won’t help reduce haze caused by smog, since smog is made up of solid particles and not reflected light. Similar to clear filters, some photographers use UV filters primarily to keep their lenses protected and clean. Check out this guide to learn more details about UV filters.

- The Only Lens Filter Guide You?ll Ever Need


_________________________________________

In the days of film the value of placing a UV filter in front of your lens was never questioned. In addition to dampening the image-robbing effects of atmospheric ultraviolet radiation, UV filters also served to protect the front element of your lens from dust and moisture. They also repelled the inevitable smudges and scratches that over time compromise the effectiveness of the antireflective coatings that go into determining how well (or not so well) your pictures turn out. Fast-forward to the modern days of digital imaging and the big argument is: “do we still need UV filters?” The answer is an unqualified “Yes.”

Despite the fact that digital imaging sensors are nowhere near as sensitive to UV radiation as film, the protective properties of a UV filter on your lens are still quite justified. Regardless of how the image is being recorded, the probability of dust, moisture, smudges and scratches finding their image-compromising way onto your front lens element is equally inevitable and troublesome.

- UV Filters | B&H Explora

_____________

personally I use UV filters only as protective filters and remove them prior to taking photos. I do this because of opinions of other members who have much more expertise than I do convinced me that was way to use UV filters

[clickclick]

Very interesting information here.

Agree - good stuff coming out.

[dcpropilot]

I have so many of them already, I may have to complete my collection of all the Pentax Jun Hirakawa lenses.

[barondla]

I have so many of them already, I may have to complete my collection of all the Pentax Jun Hirakawa lenses.

How many lenses did Jun design for Pentax? Of the Limiteds, I'm aware of the 43 & 77. The 31 came later. Was it designed by Jun? His paper only mentions the 43 & 77.
Thanks,
barondla