[stevebrot]

Lenses for film cameras are designed to maximize the resolution for that medium.

This is often claimed, but without source citation. It ignores the fact that the "medium" has traditionally been poorly defined during the so-called "film era" and the lens makers were well aware that reviews would be based at least in part on optical bench evaluation with no film being used. Simply put, they designed and built to the best manufacturing, design, and materials standards available at the time.

Available evidence suggests that the better film-era lenses were media-limited on all but the best emulsions of the day and perform appropriate to available resolution of digital sensors now. A good example might be the FA 31/1.8. The highest resolution pictoral film available when it was made was Kodak Technical Pan with a manufacturer's MTF50 of 100 l/mm. That lens was tested by photozone<dot>de at 165 l/mm on the K-5, a pretty decent performance. The D-FA 55/2.8 Macro tested at 170 l/mm on the K-5II camera. I'd say those results were within spitting distance.

So-called digital design can have different meaning depending on system. For mirrorless systems it means correcting for poor oblique light capture at the margins of the frame along with appropriate anti-reflective coatings. There are many legacy wide-angle rangefinder lenses (also short registration) that perform poorly on cameras such as the Sony A7 series as a result of the quirks of digital capture. Fortunately, dSLRs generally feature a generous registration distance with much less concern about rear element size and on-axis angles. As for coatings, the proof of that pudding would be in the eating. Most film emulsions are somewhat less reflective on the emulsion side than the surface of a digital sensor and the potential does exist for decreased contrast as a result. I have a few older (pre-1970) lenses for which this is a problem, but no particular issues with MC optics made since then.

<rant done>


Steve

[stevebrot]

Doesn't the FA 35 use glass elements and the DA 35 f2.4 use plastic? I assumed that was the reason for the difference in FF performance.

Good question. The FA 35/2 has an aspheric element, which would generally be non-glass. The same would be true of the DA 35/2.4. The two lenses share very similar design, though they differ in implementation details that probably explain performance differences.


Steve

[monochrome]

MY suspicion is the DA 70 while test chart sharp doesn't have the same $D portrait spec the 77 does. But I've never had a copy of either lens. My memory is guys wo appreciate the 70, don't appreciate the 77, and vice versa. Apparently there's two kind of people in this world to go along with the two kins who either don't like either or like them both.

Did i leave anyone out?

i like them both, but my experience is tempered by the sensors I’ve used the lenses with. I don’t like either universally.

I’ve used the FA77 on everything from a K2 through MZ-S to K-3, KP and K-1. The DA70 I’ve only used on K-3 and KP*. Consequently the impression that the DA70 is sharp and renders colors nicely, and can promote a 3D pop to a central subject may be as much the result of the pixel pitch of the 24Mp APSc sensor as of the lens’ character itself.

I’m sure most would agree the FA77 is an exceptional lens in its own right, the more so since it seems to shine on film and the lower pitch 36Mp Sony sensor. That the DA70 comes close is a big deal. At least that’s my view.


* Were it not for the DA70 and DA35/2.8 Macro I’d sell the KP and other APSc format gear and fully move to FF, but if I keep the KP for the two lenses what’s The point of selling the other three?

[BigMackCam]

MY suspicion is the DA 70 while test chart sharp doesn't have the same $D portrait spec the 77 does. But I've never had a copy of either lens. My memory is guys wo appreciate the 70, don't appreciate the 77, and vice versa. Apparently there's two kind of people in this world to go along with the two kins who either don't like either or like them both.

Did i leave anyone out?

LOL

I have the DA70 and I like it, though I don't use it all that often. The colours and contrast are lovely, it's sharp, and the out-of-focus rendering is really nice. I haven't used the FA77 but from what I've seen, it's excellent. I'd be delighted to own one, but couldn't justify it given on what the DA70 is capable of and my own creative / artistic limitations right now. If I was moving to full-frame on Pentax, maybe I'd be tempted... but then, it would be a different experience altogether, given the wider field of view

[UncleVanya]

Through a quirk of fate I own both the HD DA 70 and the FA 77 Ltd. I find them both appealing. The FA 77 gives a little more subject isolation but it isn't a huge difference. The DA 70 is a bit less prone to CA and purple fringing. They are both great lenses.

Also @monochrome - I think the DA 70 is pretty close to FF performance from what I recall reading. I do not have the K-1 to test on sadly.

[monochrome]

Through a quirk of fate I own both the HD DA 70 and the FA 77 Ltd. I find them both appealing. The FA 77 gives a little more subject isolation but it isn't a huge difference. The DA 70 is a bit less prone to CA and purple fringing. They are both great lenses.

Also @monochrome - I think the DA 70 is pretty close to FF performance from what I recall reading. I do not have the K-1 to test on sadly.

The DA70 on K-1 in FF Mode is a little dark in the corners. I’ll add something to illustrate after dinner.

[KiloHotelphoto]

I just watched the videos Tony Northrup mentioned (Crop Factor Part 1-3 from April 2106) in the video the original poster shared. In the fist video he showed pics taken with FF, crop and MFT cameras and in the second video broke down the math. In those videos he makes sense, when he shows how manufactures advertise their point and shoot cameras focal length equivalent to 35mm but not the aperture.

The one example that really stood out is for a Olympus Stylus 1 6-64mm f2.8, they advertise it as 28-300 f2.8 equivalent but it would fit in your pocket. Anyone who has seen a 300mm 2.8 FF lens knows how big they are Tony said the real equivalent for the Olympus would be 28-300 f13, it sound right to me.

I'm no engineer but the way he shows the math and examples he gives I would think you do have to multiply aperture by crop factor also.

[clackers]

Good question. The FA 35/2 has an aspheric element, which would generally be non-glass. The same would be true of the DA 35/2.4. The two lenses share very similar design, though they differ in implementation details that probably explain performance differences.


Steve

As Douglas of Sweden points out in his blogpost covering what's known of Pentax lens designers through the ages, Takayuki Sensui did "the FA35mm (which can still be bought new in the form of the slightly modified DA35/2.4)".

The DA35 has a hybrid plastic/glass aspherical element, the FA35 is one piece of glass.

http://douglasviewfinder.blogspot.com.au/p/known-pentax-lens-designs-and-designers.html

[gm4life]

Wow - this thread took off quickly. Most of what I have is crop for my APS-C kit, however I think actually an argument can be made that a crop camera with a FF lens will perform even better since it is only using the "inner" part of the image circle. Thus no soft corners etc. The F stop thing is just a load of crap. F2.8 is an F2.8, yes F2.8 is different on a full frame vs. crop BUT it is still the same F stop and will perform different just based on the size of the sensor. It doesn't mean me using the D FA 70-200 * on my K-3 II or KP isn't getting the benefit of the fast F stop, F2.8 but rather is behaving like any other F2.8 lens FF or crop on a Pentax APS-C system.

If Pentax had a decent F2.8 that went to 300mm (FF eq.) that was a crop I would have bought it, but FF was my only option. I am pleased with the D FA 70-200 * on my "humble" crop bodies. This is a load of crap - moving on.

[stevebrot]

As Douglas of Sweden points out in his blogpost covering what's known of Pentax lens designers through the ages, Takayuki Sensui did "the FA35mm (which can still be bought new in the form of the slightly modified DA35/2.4)".

The DA35 has a hybrid plastic/glass aspherical element, the FA35 is one piece of glass.

through the viewfinder: Known Pentax lens designs and designers

Well, that is interesting. It does not surprise me that the FA 35/2 is all glass. It carried a premium price tag when first released.* As for buying the FA 35/2 new...I could buy one tonight through B&H for for only $271.95 USD which is quite a bit less than it sold for about two years ago when it came back from the dead and close to what I paid when I bought mine new about eight years ago.


Steve

* Aspheric elements are difficult to produce by traditional grinding and are often the result of a combination of casting and grinding and usually results in a steep price tag.

[normhead]

This is often claimed, but without source citation. It ignores the fact that the "medium" has traditionally been poorly defined during the so-called "film era" and the lens makers were well aware that reviews would be based at least in part on optical bench evaluation with no film being used. Simply put, they designed and built to the best manufacturing, design, and materials standards available at the time.

Here's what I think, this is marketing hype. Until someone lays out the parameters in which a digital lens has to differ from a film lens I'm not buying that there even is one. What I think is happening is marketing departments are full of reasons why you should buy new lenses. Really expensive ones.

Marketing geniuses can go on and on about how these lenses are designed for digital. Until they demonstrate how that makes a difference it's just a sales pitch. My feeling is, if they had something, there'd be paper on it somewhere or one of those fake fact sheets with illustrations showing how one is different from the other, like the ones they put out to illustrate what backlit sensors are. The fact that the lens was designed for digital could mean nothing more than they don't make film bodies anymore, they just make digital bodies, so every lens they design now is designed for digital. As far as i can tell it's just market speak.

Especially true since I like the rendering of my old 35-80 as do number of other people in blind tests, although very few admit to liking it if they know what they are looking at. As far as I tell, folks are just playing games with the language, structuring sentences that seem to say one thing while saying something else.

"Designed to take advantage of digital sensors." probably means nothing more than "designed since we stopped making film cameras."

[audiobomber]

I'm no engineer but the way he shows the math and examples he gives I would think you do have to multiply aperture by crop factor also.

Correct, but some people's minds are closed to the concept, so the arguments continue. This article by DPR in 2014 did help more people to understand: What is equivalence and why should I care?: Digital Photography Review

[clackers]

Well, that is interesting. It does not surprise me that the FA 35/2 is all glass. It carried a premium price tag when first released.* As for buying the FA 35/2 new...I could buy one tonight through B&H for for only $271.95 USD which is quite a bit less than it sold for about two years ago when it came back from the dead and close to what I paid when I bought mine new about eight years ago.


Steve

* Aspheric elements are difficult to produce by traditional grinding and are often the result of a combination of casting and grinding and usually results in a steep price tag.

Yeah, I bought mine new a couple of years ago, too.

[UncleVanya]

Here's what I think, this is marketing hype. Until someone lays out the parameters in which a digital lens has to differ from a film lens I'm not buying that there even is one. What I think is happening is marketing departments are full of reasons why you should buy new lenses. Really expensive ones.

Marketing geniuses can go on and on about how these lenses are designed for digital. Until they demonstrate how that makes a difference it's just a sales pitch. My feeling is, if they had something, there'd be paper on it somewhere or one of those fake fact sheets with illustrations showing how one is different from the other, like the ones they put out to illustrate what backlit sensors are. The fact that the lens was designed for digital could mean nothing more than they don't make film bodies anymore, they just make digital bodies, so every lens they design now is designed for digital. As far as i can tell it's just market speak.

Especially true since I like the rendering of my old 35-80 as do number of other people in blind tests, although very few admit to liking it if they know what they are looking at. As far as I tell, folks are just playing games with the language, structuring sentences that seem to say one thing while saying something else.

"Designed to take advantage of digital sensors." probably means nothing more than "designed since we stopped making film cameras."

On MFT there is a bit of truth. The angle of entry to the sensor supposedly made designing wide angle lenses complex due to the close proximity of the rear element to the sensor and the interaction of this with the color filter. This isn't a problem with adapted lenses typically since they are farther from the sensor. But it is true that the digital lenses had to be designed with this angle in mind.

[stevebrot]

On MFT there is a bit of truth.

...Yes, and on FF mirrorless with some legacy wide-angle rangefinder lenses. These lenses typically are not retrofocus and feature rear elements that are often quite close to the sensor. Lensrentals has published a summary document with compatibility list.

Lens Rentals | Blog


Steve