[cbope]

Now that everyone is drooling over K1, myself included, it would be great to start a lens compatibility list and sticky it in this section and also in the lens section:

- Lenses that are fully compatible, covering FF image circle wide open
- Lenses that have mild to moderate vignetting, but can either be fixed in post or by stopping down 1-2 stops
- Lenses that should not be used on FF unless crop mode is used

I know that some of this info can be found in some of the lens reviews here, but it's really difficult digging it out and the information is missing in some reviews if I recall...

It would be great to have this list!

Anyone?

[Na Horuk]

A recent thread asking this: https://www.pentaxforums.com/forums/190-pentax-k-1/314261-so-lenses-work-k-1-a.html

Another thread, with answers (new, with nice pictures): www.pentaxforums.com/forums/169-pentax-full-frame/313830-current-pentax-k-ff-lenses-overview-picture.html

Original test thread from years ago (some lenses are missing in first post, but can be found within thread): https://www.pentaxforums.com/forums/54-pentax-lens-articles/31629-da-lenses-f...ts-thread.html

Third party FF lenses (again, old first post, but more within thread): https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/183420-curr...me-lenses.html

[Sandy Hancock]

^ What he said.
And I said on Facebook....

[UncleVanya]

Maybe what would be useful is the ability to mark lenses FF or not in the reviews section along with a caution to only do so if you have actually used the lens on a FF.

[Na Horuk]

Maybe what would be useful is the ability to mark lenses FF or not in the reviews section along with a caution to only do so if you have actually used the lens on a FF.

There is this option. Go to PF Lens review database and hit Search on the right side. It will lead you here: Search - Pentax Lens Reviews & Lens Database
Now you can select image format ( as well as other things like Mount, "In production", and so on)

[HoustonBob]

Along with the coverage concerns are the quality concerns of some older film lenses. This has been an issue with the 36 megapixel Nikon cameras, and since the K1 doesn't have the blurring of an anti-aliasing filter it has a potential to be a problem on the K1. One big advantage of the K1 over the 36 mp Nikon cameras is the in body stabilization of the K1. Part of the problem with the non stabilized Nikon approach is that the increased resolution means the old "one over the focal length" shutter speed rule of thumb really becomes "one over twice the focal length" or maybe even "one over 4 times the focal length" for 36 mp. The IBIS of the K1 will tend to make older lenses more usable on the Pentax than on high end Nikon bodies.

[Zephos]

Quick question: How does stopping down change the size of the image circle? I thought that was constant.

[Na Horuk]

Quick question: How does stopping down change the size of the image circle? I thought that was constant.

A couple of things can change it. Zoom and focus settings are the first. Most lenses are designed to simply have an acceptable image circle at the smallest size, and then at the other settings, the rest is just wasted. I think this is why some modern lenses have a duffle on the back. Its like a lens hood, but on the back, so that stray light doesn't affect contrast and IQ in general. Some APSC zoom lenses are fine on FF at some focal length and focus settings, but have a big vignetting issue on others.
Aperture has a small effect, but rather small.
Lens hood can also cut the image circle, particularly with ultra wide lenses. And a very tight circular lens hood can even act as an aperture. This is particularly noticeable with widest apertures on wide angle lenses. Stopping down tends to "equalize" the image circle (reduce CA, reduce vignetting). Can't really explain it any better than that. Of course, stopping down too much will cause diffraction and soften the image.

[npc]

Along with the coverage concerns are the quality concerns of some older film lenses. This has been an issue with the 36 megapixel Nikon cameras, and since the K1 doesn't have the blurring of an anti-aliasing filter it has a potential to be a problem on the K1. One big advantage of the K1 over the 36 mp Nikon cameras is the in body stabilization of the K1. Part of the problem with the non stabilized Nikon approach is that the increased resolution means the old "one over the focal length" shutter speed rule of thumb really becomes "one over twice the focal length" or maybe even "one over 4 times the focal length" for 36 mp. The IBIS of the K1 will tend to make older lenses more usable on the Pentax than on high end Nikon bodies.

The part about the quality of old lenses is ture, but the problem about 36 mpix resolution and increased risk of blur due to shake just does not exist.

I've shot AR7and D800E alongside K5IIs (all non-AA filter, about the same pixel size) for long enough to confirm that I'm not getting more blurred images due to shake under reasonable lightning conditions than with the K5IIs (and that is with K5IIs SR on ).

Probably K-3's 24mpix sensor is more demanding in that respect

---------- Post added 02-20-16 at 01:35 PM ----------

A couple of things can change it. Zoom and focus settings are the first. Most lenses are designed to simply have an acceptable image circle at the smallest size, and then at the other settings, the rest is just wasted. I think this is why some modern lenses have a duffle on the back. Its like a lens hood, but on the back, so that stray light doesn't affect contrast and IQ in general. Some APSC zoom lenses are fine on FF at some focal length and focus settings, but have a big vignetting issue on others.
Aperture has a small effect, but rather small.
Lens hood can also cut the image circle, particularly with ultra wide lenses. And a very tight circular lens hood can even act as an aperture. This is particularly noticeable with widest apertures on wide angle lenses. Stopping down tends to "equalize" the image circle (reduce CA, reduce vignetting). Can't really explain it any better than that. Of course, stopping down too much will cause diffraction and soften the image.

Actually, on FF some APS-C lenses that borderline cover FF - stopping down makes the image circle smaller. Or actually maybe it just makes it more sharp and well-defined, but the end result is that wide open they have some vingetting but stopping down it turns to dark corners. For example DA 12-24 behaves like this somewhere in the 20-24 range and also the 35 ltd at non-macro distances.

[HoustonBob]

The part about the quality of old lenses is ture, but the problem about 36 mpix resolution and increased risk of blur due to shake just does not exist.

I've shot AR7and D800E alongside K5IIs (all non-AA filter, about the same pixel size) for long enough to confirm that I'm not getting more blurred images due to shake under reasonable lightning conditions than with the K5IIs (and that is with K5IIs SR on ).

Probably K-3's 24mpix sensor is more demanding in that respect

---------- Post added 02-20-16 at 01:35 PM ----------



The "one over focal length" equal minimum shutter speed rule of thumb comes from making a blur small enough that film (about 8 megapixel resolution for color film) won't show the motion blur. As megapixels climb that motion blur has to be reduced in size or you aren't getting all of the resolution that the system can produce. The only way to do that on non stabilized equipment is with faster shutter speeds. The motion blur problem is worse on a K5II than on film because of the extra resolution.

Let me explain something that might be skewing your results. "One over the focal length" is only a rule of thumb because some people can hold steady better than others. When I was young I could hold a 50mm at about a 15th of a second without problems. As I am no longer young and tremble some - that is no longer true. Just because you can hold a D800E steady with no stabilization does not mean I can - or even that most people can. Holding a 50mm lens steady enough to not show motion blur on a D800E at 1/50th of a second requires the equivalent of what I used to be able to do on film; about a film steadiness of 1/15th of a second. The two stops of extra resolution compared to film require more steadiness to achieve them - the acceptable motion blur on film has to be bigger than on something with four times the resolution. The requirement for more shake reduction with increased resolution is why the K1 has 5 stops of image stabilization.

Look at it this way: 35mm color film will produce 20/20 results; that is if you blow the picture up to where it appears the same size as a real object - a person with 20/20 eyes will be able to see all the detail in the picture that he could looking at the actual object. A K1 or D800E has the equivalent of 20/5 vision; the picture shows more detail than the eye can see at a life size reproduction. 20/20 is considered normal vision because beyond that requires a steadier eye than most people have.

[Class A]

- Lenses that are fully compatible, covering FF image circle wide open

I have compiled a list of FF lenses that are currently in production.

It differs from the list in https://www.pentaxforums.com/forums/169-pentax-full-frame/313830-current-pent...w-picture.html in that it excludes lenses like the Sigma 70/2.8 macro which have been retired by the lens manufacturer.

I'm not trying to diminish the significance of legacy lenses -- some of them are the best you can get for the K-1 -- but I was interested in compiling lenses that are in current catalogues of lens manufacturers.

[npc]

---------- Post added 02-20-16 at 01:35 PM ----------



The "one over focal length" equal minimum shutter speed rule of thumb comes from making a blur small enough that film (about 8 megapixel resolution for color film) won't show the motion blur. As megapixels climb that motion blur has to be reduced in size or you aren't getting all of the resolution that the system can produce. The only way to do that on non stabilized equipment is with faster shutter speeds. The motion blur problem is worse on a K5II than on film because of the extra resolution.

Let me explain something that might be skewing your results. "One over the focal length" is only a rule of thumb because some people can hold steady better than others. When I was young I could hold a 50mm at about a 15th of a second without problems. As I am no longer young and tremble some - that is no longer true. Just because you can hold a D800E steady with no stabilization does not mean I can - or even that most people can. Holding a 50mm lens steady enough to not show motion blur on a D800E at 1/50th of a second requires the equivalent of what I used to be able to do on film; about a film steadiness of 1/15th of a second. The two stops of extra resolution compared to film require more steadiness to achieve them - the acceptable motion blur on film has to be bigger than on something with four times the resolution. The requirement for more shake reduction with increased resolution is why the K1 has 5 stops of image stabilization.

Look at it this way: 35mm color film will produce 20/20 results; that is if you blow the picture up to where it appears the same size as a real object - a person with 20/20 eyes will be able to see all the detail in the picture that he could looking at the actual object. A K1 or D800E has the equivalent of 20/5 vision; the picture shows more detail than the eye can see at a life size reproduction. 20/20 is considered normal vision because beyond that requires a steadier eye than most people have.

I've misunderstood your original post. I assumed it is about switching from current DSLRs like K5, K3, etc. to K-1 because I've read similar concerns in the other forums when the first 36mpix cameras started to appear few years ago. I was somewhat concerned too going from K5IIs to D800E (and then ultimately to A7R) to but time has shown that I'm not getting similar results from them at similar shutter speeds. Of course for every person has his own limit here shake blur will start to show.

---------- Post added 02-21-16 at 03:39 AM ----------

- Lenses that have mild to moderate vignetting, but can either be fixed in post or by stopping down 1-2 stops
- Lenses that should not be used on FF unless crop mode is used

I guess more detailed information and tests will start to appear once K-1 starts shipping.
DA lenses are kind of pain to use on other brands FF cameras or at least you are never sure what exact f-stop you are shooting.

But I think the "good performers" are already known from multiple posts (after all, the DA lineup is not that huge), and how much of the projected image beyond APS-C can be salvaged from the others really depends on what people personally find acceptable performance.