[Fenwoodian]

I have already Leitaxed 3 Zeiss ZF (Nikon mount) lenses and am now using them on my Pentax K1 camera. I feel that the Leitax mounts result in a better/tighter fit than do most of the Pentax glass I have used on my K1.

All of these Sigma lenses you want (20mm, 24mm, 50mm, 85mm, etc.) are already available in the Nikon mount. However, don't hold your breath for Leitax (or anyone else) to develop a Sigma Nikon F to Pentax K adapter. One insurmountable problem - none of the Sigma Art lenses have "manual aperture rings".

[bdery]

I think Sony, Panasonic & Olympus 4/3 lenses are full interchangeable.

Yes. Except that now they moved to ANOTHER "standard". i.e. micro 4/3, but they don'T seem to be working together at all.

[Kunzite]

Sony?

[Rupert]

Yeah, if the 150-600 were offered it would be on its way to my house right now. It would be my long distance choice for my K3.

Me too!

I thought I read somewhere that for a fee Sigma will make you a lens of your choice in K-mount? Was I just dreaming that?

[FantasticMrFox]

Of course, then the next question is which non-K-mount Sigma lens would attract the greatest number of pre-orders.

Based on which Sigma lenses are particularly popular in general and what Pentax is missing in their lineup my educated guess would be:

20 f/1.4 'Art' (no current Pentax alternative)
24 f/1.4 'Art' (no current Pentax alternative)
50 f/1.4 'Art' (superior optically to any current Pentax alternative)

50-100 f/1.8 'Art' (no current Pentax alternative)
150-600 f/5-6.3 Contemporary/Sport (affordable alternative with more reach than Pentax D FA 150-450)

[RobA_Oz]

An 18mm on FF would be an awfully wide field of view. I'm not saying that some folks wouldn't appreciate that, but I think it's beyond what a lot of folks would be looking for. Looking through the lens database, the FA 20 f2.8 has a wider horizontal field of view on FF than the 15 Ltd. does on APS-C. So it stops being so general purpose with that much width. At least, that's my thinking, based on the 300 or so shots I've taken with my recently acquired 15.

The FA* 24 f2.0, on the other hand, is just a few degrees less wide than the 15 when doing this same comparison. That's why I'm thinking a 24mm for FF makes sense. I'd give up that .0 and replace it with a .8 on the max aperture to try and get the size and weight back down a bit. What I don't really want is another f4 max lens that isn't so hot in low light. It's a trade-off.

I have both the FA20/2.8 and the FA*24/2. Using another APS-C lens as a reference, the FA20 on 35FF is only marginally wider than the DA14 on APS-C. The FA20/2.8 and the FA*24/2 have the same filter size (67mm) but the FA20 at 255g is considerably lighter than the FA*24 at 405g. The difference seems to be between the metal body of the 24 and the plastic of the 20 (although, by way of comparison, the A24/2.8 with a metal body weighs 205g). Both feel fine on the K-1, just the same.

[Venom3300]

Me too!

I thought I read somewhere that for a fee Sigma will make you a lens of your choice in K-mount? Was I just dreaming that?

Only if the lens was originally offered in k mount. Otherwise they dont have the parts to do it.

[bigdavephoto]

To be a realist here, lets say, one thousand members sent letters and or emails to Sigma, saying that they would buy X lens or Y lens if it is made with a Pentax mount isn't going to change there minds about supporting Pentax.


What would change there minds is people buying the Sigma lenses already made with a Pentax mount. It all comes down to money. Sigma is not going to change the production lines if they are only going to sell 50 85mm art lenses and not make a profit. Everybody needs to remember that when we buy lenses, we are paying for the designing of the lens plus the tooling to make the lens and the people to put it together. If Sigma knew for a fact that they would sell 1,500 85mm art lenses with a Pentax mount in the next 2 to 3 months, they might consider making them with a Pentax mount.

[normhead]

My DA*200 with the 1.4 and 1.7 TCs on my K-3 give me the same field of view as a 700mm lens on a K-1.

So honestly, I don't get the love for the 150-600.

My DA*200 with HD DA 1.4 TC and F 1.7x AF Adapter stacked = 476mm x 1.5= 714mm ƒ6.3 and 1200 grams.

DA* 200mm 994 grams. Darn near half the weight. 200mm ƒ2.8 compared to 200mm ƒ5 at 1930 grams.

Sigma 150-600 @600mm ƒ6.3 1930 grams, 700 grams more, for less reach That is more than pound and 2/3s more weight.

Honestly, I'm scratching my head here... why do you think a 150-600 is such a great thing? Worth switching brands for? Worth complaining it's not there? I'm not buying it, a lot of Pentax owners aren't buying it.

I'm willing to start my own petition entitled "Sigma, take your 150-600 and shove it."
I gain a lot of weight to carry going K-1 and 150-600, and I lose a lot of reach.

You guys could have an SDM DA* , 200 or 300, that are being phased out right now, for a lot less money. I've never seen Sigma zoom that came anywhere close to matching a Pentax prime. To my mind, a Pentax prime with a couple of TCs is at least on par and probably much better than a Sigma zoom, and right now, not even that much more money. even with the TCs.

I went through he math on this over and over again before I got the DA*200. My money is where my mouth is.

[VoiceOfReason]

My DA*200 with the 1.4 and 1.7 TCs on my K-3 give me the same field of view as a 700mm lens on a K-1.

So honestly, I don't get the love for the 150-600.

My DA*200 with HD DA 1.4 TC and F 1.7x AF Adapter stacked = 476mm x 1.5= 714mm ƒ6.3 and 1200 grams.

DA* 200mm 994 grams. Darn near half the weight. 200mm ƒ2.8 compared to 200mm ƒ5 at 1930 grams.

Sigma 150-600 @600mm ƒ6.3 1930 grams, 700 grams more, for less reach That is more than pound and 2/3s more weight.

Honestly, I'm scratching my head here... why do you think a 150-600 is such a great thing? Worth switching brands for? Worth complaining it's not there? I'm not buying it, a lot of Pentax owners aren't buying it.

I'm willing to start my own petition entitled "Sigma, take your 150-600 and shove it."
I gain a lot of weight to carry going K-1 and 150-600, and I lose a lot of reach.

You guys could have an SDM DA* , 200 or 300, that are being phased out right now, for a lot less money. I've never seen Sigma zoom that came anywhere close to matching a Pentax prime. To my mind, a Pentax prime with a couple of TCs is at least on par and probably much better than a Sigma zoom, and right now, not even that much more money. even with the TCs.

I went through he math on this over and over again before I got the DA*200. My money is where my mouth is.

Using your math the Sigma @600mm = 900mm on APSC. Now add the 1.4 tc on that and it would make a monster astrophotography setup. That's pretty much what I would use it for too. Right now I use the DFA 150-450 and 1.4tc and I'd love more reach, and a telescope is a real PITA to haul out, set up, use the proper adapters, etc on, and the easier ones to use for that (refractors) have real problems with CA on bright objects unless you get a more expensive triple apochromatic one.

I don't want the lens for wildlife, I want it because it corrects many of the problems you have with telescopes at a traction of the price for the focal length.

---------- Post added 07-29-16 at 09:14 AM ----------

Here's the closest I can get to what the Sigma stacked with a TC would be, and the Sigma would be much more useful for other things too:

Orion Telescopes: Orion EON 130mm ED Triplet Apochromatic Refractor Telescope

[normhead]

My math includes the part where you can't get reliable auto-focus on a 6.3 lens using a TC. But, in turning the ens into a manual focus lens I guess you might have a point.

So, I'm not sure you've got it right. What you imagine to be the case, has not proved to be the case with any field tests I've done. Regardless of what you might think, putting the 1.7 on a 5.6 lens doesn't really work. However, putting it on the 1.7 and 1.4 on a 2.8 lens gives you lightning fast AF, using the AF adapter as a focus limiter. Your math needs to be informed by what functions you lose.

What we were discussing here was birding. The lack of AF in birding is critical.the Sigma 150-600 @ 6.3, with a 1.4 TC is now 9 9.7 or something like that. That restrict suse of the lens for a lot of purposes, including netting that requires shutter speed to reduce subject motion blur.

I'll believe a Sigma 150-600 is better for astro-photography, when I see the comparison images that prove it. I don't ;own the 150-600 but the Sigma long lens zooms I have owned have been mush at the long end. Not even functional straight up, forget about with their imperfections magnified by a TC.

IN any case, you you don't even want a lens, you want a telescope, which are for th most part much simpler pieces of equipment. That almost makes you out of qualifying for comment in a discussion of phot lenses, at least in terms of relevance to the average shooter.

I'm interested in your speculation, but given past experience, I'm going with "show me this works before I buy." Even if I wanted it as a telescope, I'd want to see results before I started posting that it will be a good purchase in that regards. I'm talking about what works for me, not what I think might work if I actually had the gear.

[VoiceOfReason]

Well, here's a shot of the moon with the Pentax 150-450 @450 with the 1.4tc on it using the K3, and it did AF. When I had the Sigma 150-500 it would also AF with the 1.4 in halfway decent light.

I do have telescopes, a Meade Coronado PST, a 130mm Newtonian reflector with go to, an 8 inch Dobsonian reflector, and a 10 inch Schmidt Newtonian with go to. The problem is that you get a lot more CA than I like (and correct in pp) with one. This is not a problem with a lens because of all the correction in the lens. Also, not everyone is going to use a lens for the same thing, so my use is just as valid as yours.

[normhead]

Also, not everyone is going to use a lens for the same thing, so my use is just as valid as yours.

Well not really. I'd say your conclusions might be more valid for astrophotography, I would expect mine will be more valid for wildlife, birding, and general use.

No where in this discussion is anyone advocating anything above a 150-450 with a 1.4. That's simply top of class for a 600mm zoom. Is that relevant to a long Signa zoom? I doubt it.

But just generally, I'm quite willing to say, if your astro photgraphy is more than a proof of concept moon shot every now and then, sure I will look at your images. Will I look at a lens that would cost me close to $3000 with a 1.4 as proof of concept of a 150-600 being a necessary part of someone's lens arsenal?

Nope. I already know a 1.4 will work with a 150-450. It will also work with my A-400. However go to the A-400 5.6 and the 1.7 to make ƒ 9.3, and the AF is no longer accurate or dependable.

So from my experience, the 150-450 will work with the 1.4, but nothing greater than that. And my guess based on the A-400 which does work with the 1.4 but not with the 1.7 would be, you are going to lose AF going to an ƒ6.3 lens. Astrophotography can be done with MF. There's not need for AF at all. I fail to see how it can be relevant to discussing the AF module in a camera system.

Your use is just as valid, just to far fewer people, and invalid to many more people.

For me, there has been a practical line in the sand, ƒ5.6 or faster to use the 1.4 TC. The 150-450 fits that criteria, the 150-500, 50-500 and 150-600 do not. But If someone wants to post some images and text that prove me wrong, I'll be the first to change my mind. It just hasn't happened yet.

[Lowell Goudge]

when i read all the threads, there is one thing that is missing in the discussion. specifically, what is the current installed base of pentax cameras, this means from *istD to K1 inclusive, assuming that after 5 years old no one will purchase a new lens for an old body.

how many lenses has sigma made, in pentax, and here, you can assume they are all still in service since lenses remain in use much longer than cameras, I know, i bought my 70-200/2.8 and 10-20 within a year of getting an *istD in december 2003, and while i do still take out the *istD from time to time, the lenses get a ton of use still, 13 years later,

i think if you look at it objectively, the k mount market is somewhat saturated, with sigma's existing lenses, so except for some new ones, and i am not sure the current zoom out to 600mm is enough over their various offerings that go to 500mm to make a difference, there is just not a lot of room left.

i simply dont believe the demand is there, and unless there is a massive swing inmarket share, which i do not believe because changing out lens systems is very expensive, and the new people into slrs are declining, we will have to exist with deminishing returns, i.e. less not more lens offerings. \
\
the best we can hope for is a bonehead move by either canon or nikon, where they decide to change lens mounts and drive their customer base elsewhere. canon does have a history of this,

[bdery]

i think if you look at it objectively, the k mount market is somewhat saturated, with sigma's existing lenses

This reasoning isn't wrong per se, but does not take into account the improvements made with new designs. For instance the Sigma 17-70 V1 has been my main lens for at least 8 years, but it did start to show its age when live view AF became common. I sold it cheap and purchased a new lens (in this case, the Pentax 16-85 because of WR). So even current owners can and will spend more money even if they already own glass.

i simply dont believe the demand is there

Sigma appears to agree.