[normhead]

Officially only a very few lenses that are called DA rather than DFA are considered Full Frame (FF). All of those that Pentax considers FF have in camera correction profiles for both apsc and FF. Additionally users have found many DA primes over 30mm are reasonably FF.Most DA zooms are not. See here: Full Frame Coverage of DA Lenses: Comprehensive Test - Gear Guides | PentaxForums.com

Many DA lenses especially the 30s 40s 50s, the 300 etc.were derived from FF lenses, and the size of the image circle wasn't changed.

[UncleVanya]

Many DA lenses especially the 30s 40s 50s, the 300 etc.were derived from FF lenses, and the size of the image circle wasn't changed.

While that’s true tests suggest that reduced size baffles (35f2.4, 60-250) impact this. The lack of ff correction profiles also suggests that Pentax has not decided to consider these as ff. Personal use suggests the da 40, da 55, and da 70 are reasonably useable on my Sony A7riii so I get your point. My point is that there are only three or so that Pentax fully supports for FF. Additionally this article gives clear test results that should help people plan and verify their own lenses applicability for FF use.

[normhead]

While that’s true tests suggest that reduced size baffles (35f2.4, 60-250) impact this. The lack of ff correction profiles also suggests that Pentax has not decided to consider these as ff. Personal use suggests the da 40, da 55, and da 70 are reasonably useable on my Sony A7riii so I get your point. My point is that there are only three or so that Pentax fully supports for FF. Additionally this article gives clear test results that should help people plan and verify their own lenses applicability for FF use.

The DA*60-250 was designed as an FF lens, but the baffle was added afterwards. It was never an FF lens before. The 40XS was never baffled. Each circumstance is different.

[UncleVanya]

The DA*60-250 was designed as am FF lens, but the baffle was added afterwards. It was never an FF lens before. The 40XS was never baffled. Each circumstance is different.

I don’t disagree at all. I think we are in agreement- many DA primes from 35mm and up are adequate on FF - some are not. DA 35 macro is one that I’ve seen poor fit results to FF. The DA 40 is softer in corners than some but reasonable. The DA 21, 15, 14 are all not FF. the zooms are mostly a mess except for the da 60-250. Some like the 10-17 or 12-24 are surprising in that the “long” end isn’t too bad on FF.

[clackers]

While that’s true tests suggest that reduced size baffles (35f2.4, 60-250) impact this. The lack of ff correction profiles also suggests that Pentax has not decided to consider these as ff. Personal use suggests the da 40, da 55, and da 70 are reasonably useable on my Sony A7riii so I get your point. My point is that there are only three or so that Pentax fully supports for FF. Additionally this article gives clear test results that should help people plan and verify their own lenses applicability for FF use.

UncleVanya, I think it's a pretty poor article, because it does not acknowledge that full frame means full frame lenses don't cover the image circle, that's the norm.

The mighty FA31 doesn't. It has 2 eV fall off in the corners. Zeisses don't. The Sigma 35mm Art f1.4 would be a fail by those standards. I suspect the DA*55 covers the full frame better than the FA50.

If you really want to see the little DA35 on full frame, you only have to check out real Pentax photos shot by Ricoh in testing in full frame mode on the K-1 here. You can see it doesn't need any in camera profile.

PENTAX K-1 Laboratory | PENTAX K-1 Special site | RICOH IMAGING

It's a sort of Canon and Nikon illness, this DX vs FX, you're a piece of worthless crap if you don't pay the corporation extra and upgrade to full frame. Pentaxians I believe are more nuanced than that, and understand that many of *our* DA lenses actually have FA heritages, they were full frame to begin with.

You can best understand the DA40SX as a grandchild of the ancient M40 f2.8 pancake.

[clackers]

Here are the Ricoh tests with the DA*60-250. The current reissue has the baffle redesigned, but these shots would've been with the old one.

http://k-1-lab.com/en/smc-pentax-da-s-60-250mm-f4ed-if-sdm

[UncleVanya]

Here are the Ricoh tests with the DA*60-250. The current reissue has the baffle redesigned, but these shots would've been with the old one.

PENTAX K-1 Laboratory | PENTAX K-1 Special site | RICOH IMAGING

What reissue????

---------- Post added 10-07-21 at 11:34 PM ----------

UncleVanya, I think it's a pretty poor article, because it does not acknowledge that full frame means full frame lenses don't cover the image circle, that's the norm.

The mighty FA31 doesn't. It has 2 eV fall off in the corners. Zeisses don't. The Sigma 35mm Art f1.4 would be a fail by those standards. I suspect the DA*55 covers the full frame better than the FA50.

If you really want to see the little DA35 on full frame, you only have to check out real Pentax photos shot by Ricoh in testing in full frame mode on the K-1 here. You can see it doesn't need any in camera profile.

PENTAX K-1 Laboratory | PENTAX K-1 Special site | RICOH IMAGING

It's a sort of Canon and Nikon illness, this DX vs FX, you're a piece of worthless crap if you don't pay the corporation extra and upgrade to full frame. Pentaxians I believe are more nuanced than that, and understand that many of *our* DA lenses actually have FA heritages, they were full frame to begin with.

You can best understand the DA40SX as a grandchild of the ancient M40 f2.8 pancake.

I think you are seriously misrepresenting that article. -2EV? That’s not “heavy” vignetting and the 31 certainly doesn’t have blurry unacceptable corners. That article gave “A” ratings to the 60-250 unmodified. I have personally not used the k-1 with this article in hand, but the results of using my lenses on a Sony FF seem to align reasonably well to this. As for correction profiles, some lenses benefit from them, Pentax probably SHOULD create them for DA lenses shot on the k-1.

No one is disputing that many da lenses are capable of creating good images in ff mode - but not every lens works fully at every f stop and focus distance.

Taking this further, The fa* 300 fitted with the hd da 1.4x is ok at certain distances wide open - a heavy vignette, but acceptable. Stop down to f8 and you have a hard black circle in the frame. Until I actually shot in the f8 condition I didn’t realize it was that bad. Mind you I wasn’t testing it, I was just using it. Testing to understand it came later. Systematic testing at multiple f stops and focus distances is far more convincing than anecdotal images. I do wish example photos were given for each rating however.

[clackers]

What reissue????

Apologies, UV, I have no idea why I thought the DA*60-250 had been reissued. In fact, the Tamron 70-210 can be seen as supplanting or replacing it!

No one is disputing that many da lenses are capable of creating good images in ff mode - but not every lens works fully at every f stop and focus distance.

My point is in your last phrase.

Not even full frame lenses work fully at every f stop and focus distance.

2eV is *bad* for the FA31, but it is perhaps typical. We see poor corners in a way we don't in APS-C.

The Leica Summicron 50mm f2 even has 2.7eV drop off. Is it full frame or not?

What about the Zeiss 21mm and Samyang 14mm? Have a look at the controlled results below:

[BigMackCam]

My point is in your last phrase.

Not even full frame lenses work fully at every f stop and focus distance.

2eV is *bad* for the FA31, but it is perhaps typical. We see poor corners in a way we don't in APS-C.

The Leica Summicron 50mm f2 even has 2.7eV drop off. Is it full frame or not?

What about the Zeiss 21mm and Samyang 14mm? Have a look at the controlled results below:

Hope you fellas don't mind me jumping in here...

Perhaps I'm incorrect, but if a lens covers the full image circle with reasonable optical performance and only soft vignetting (as opposed to the hard cut-off we get from, say, a circular fish-eye) then IMHO it can be considered compatible with the format. When there's hard vignetting or unacceptable optical performance in the borders (and I realise that last point is somewhat subjective), then I don't consider it compatible...

Just my two cents, of course

[pinholecam]

I don't really care much about equivalence.

I pick up a camera for whatever format, with its lens/es frame the photo, adjust the settings to my needs and take the photo.
Too narrow, move back, too wide, move in.
I don't lament along the lines of "If it was the TRUE focal length, I would have got a better photo! "

I do appreciate that with a format like FF, it can be easier to get a desired shallow DOF for the FOV look, but I just don't like to whine over some made up "What it could have been" or "Ultimate truism"

[slartibartfast01]

This thread seems to have deviated from the original question which was purely about equivalent focal length not about equivalence regarding depth of field.

[northcoastgreg]

Perhaps I'm incorrect, but if a lens covers the full image circle with reasonable optical performance and only soft vignetting (as opposed to the hard cut-off we get from, say, a circular fish-eye) then it can be considered compatible with the format.

No, you're not incorrect. But there are other issues involved. Performance is not only subjective for users, but for the manufacturer as well. Pentax has their own ideas of what qualifies as a DFA lens, and they may be particularly fastidious as to what qualifies either at DFA star lens or a DFA limited. The DA* 55 may be a legitimate DFA lens in that it covers the FF circle and covers it reasonably well—but Pentax may not regarded it's performance outside the APS-C circle as good enough to qualify for the star designation, which means they can't honestly market it as the DFA* 55/1.4.

Now I'll admit that I have very little interest in using DA lenses on FF. I have used the DA 1.4 converter on FF, but that's for critter images which don't require sharp edges and often need to be cropped in any case. I've also used the DA 35 Ltd on FF as a macro lens. It works fine at close distances but is unusable, for my purposes, at longer distances. I mostly use FF to get the highest quality landscape images edge to edge, and I'm not inclined to compromise on that. In many respects I prefer the APS-C format for the smaller size of the cameras and lenses, so if I'm going to bother with the larger, heavier FF format, it has to pay better dividends across the entire FF frame, not just in the APS-C part of it. When I first acquired the K-1, I tried the DA 10-17 on it, and while that lens "covers" the FF frame from 14mm to 17mm, I found the performance outside the APS-C image circle to be appalling. I could capture more detail toward the edges using that lens at comparable focal lengths on APS-C. So I ended up tracking down a copy of the F 17-28 for use on the K-1, and that lens really does deliver FF performance across it's entire zoom range on the K-1 with little in the way of unpalatable compromise.

[Rondec]

So, will the magnification not be greater with the ASP-C body? I would like to see a side by side comparison of, say, the Pentax 55-300 lens taking a pic at max focal length on aps-c vs. ff

This example comparison pretty much tells me that magnification will be greater on smaller sensors if the same lens were used, eh?

When you shoot with APS-C you are cropping -- nothing more or less. It would be like taking a film negative and trimming the outer third away from it. Does it make your lens longer? No, it doesn't. It does make the angle of view you see with your lens roughly the same as a lens with 1.5 times as long focal length on a full frame camera.

How much detail you see in your images and whether the APS-C has more detail in its cropped image is totally dependent on how many megapixels it has. If it has 24 or 26 megapixels it will have a little more detail than an APS-C crop of a K-1 (36 megapixel) image. If it is a higher megapixel full frame sensor then there may be little difference if you choose to crop the full frame image down to the APS-C crop.

At the end of the day, APS-C or micro four thirds doesn't make your lenses longer or provide more magnification. It only means that lenses have a more narrow field of view compared to shooting a lens with the same focal length on a camera with a larger sensor.

[Lord Lucan]

I pick up a camera for whatever format, with its lens/es frame the photo, adjust the settings to my needs and take the photo.Too narrow, move back, too wide, move in.

You post some superb pictures here, and I notice that you have a style that many are from the balconies of skyscrapers or with water immediately in front. I don't think moving closer would have been an option

[photoptimist]

The Leica Summicron 50mm f2 even has 2.7eV drop off. Is it full frame or not?

It's fully compatible with full frame film, but less so with full frame digital.

A number of very nice, compact primes from the film era have short exit pupil distances (the optical distance from the aperture in the lens to the plane of focus). When the lens is wide-open, the angle of refraction is so sharp, that some of the light from the lens bounces off the sensor instead of being captured by the microlenses on the pixels of sensor.

Technically speaking, it's not the main lens that is vignetting, it's the tiny microlenses. One could say that it is the camera that's not compatible with some full frame lenses!