[wadge22]

On a K5IIs this is a 750mm lens!. That is a nice long lens. the 300mm with a 1.4TC is only 420mm so that is still shorter that what you have.

If the sigma "is a 750mm lens" because you use it on a crop camera, then the 300+tc "is a" 630mm lens. Still shorter, but not by a ton, and probably better IQ.
If you use a 1.7 tc with your 300 f4, that's a 510mm (765mm equiv). And again, should be pretty good IQ for the smaller package.

[Lowell Goudge]

If the sigma "is a 750mm lens" because you use it on a crop camera, then the 300+tc "is a" 630mm lens. Still shorter, but not by a ton, and probably better IQ.
If you use a 1.7 tc with your 300 f4, that's a 510mm (765mm equiv). And again, should be pretty good IQ for the smaller package.

It’s funny but this same discussion is going on in another thread.

Here is my post with links to shots with the K300/4 and 1.7x AF converter

Takumar 300mm vs. SMC 300mm - your opinion(s) please - PentaxForums.com

[Des]

I'm looking for good IQ at 300MM. The 50-500 is ok but I want to upgrade to a nice fixed 300mm lens that has great IQ reviews

The F*300 f4.5 or FA*300 f4.5 are also worth considering, as others have said, if you find a good one at a decent price. I have the FA*300 and I like the IQ, weight and compact size. The screw-driven AF has the advantage of reliability. It's not too noisy as screw-driven AF goes (not like the coffee grinder sound of my old DA L 55-300 f4-5.8). It lacks a tripod foot, but you can get aftermarket ones. If you don't mind the extra weight and bulk, the DA*300 is probably more desirable for the reasons Sandy mentioned - weather-sealing, quiet AF, QS - plus included tripod mount and one-third stop of aperture. The aperture difference is not trivial, especially for use with a TC - 420mm f5.6 will often be able to focus better than 420mm f6.3.

One sting in the tail with the 300mm prime option is that the DA 1.4x TC is so expensive. You can use cheaper third party TCs (I have the Kenko Pz-AF 1.5x Teleplus SHQ, which works with PLM or SDM AF) but the camera doesn't know it's there, which affects the SR. If you get a new DA 1.4x TC and a new DA*300 f4, it's not that much cheaper than a DFA 150-450.

I have the smc Pentax DA 55-300 F/4-5.8 ED

The resolution on my old DA L 55-300 was very good. The main difference in IQ with the PLM is not so much about resolution (although I think the PLM is better wide open) but that the latter renders better. And of course its AF is streets ahead. But with a K-5iis, you could only shoot wide open.

This raises another question. Have you thought about getting a 24mp body like the K-3? There's a big advantage in having more pixels for cropping, plus it opens up the option of KAF4 lenses.

[cdw2000]

A brief comment … the OP's picture shows the camera with a neck-strap and the big lens fitted. I've always been of the option that this combination can induce excessive strain on the lens mount.
I have my strap fitted to the lens' tripod mount, there's a little bar just fit for this purpose

I just acquired the 50-500mm Bigma and am interested in how you have your strap setup. When you say "the bar" are you talking about the shaft of the screw used to tighten the tripod mount collar?

[kypfer]

I just acquired the 50-500mm Bigma and am interested in how you have your strap setup. When you say "the bar" are you talking about the shaft of the screw used to tighten the tripod mount collar?

Exactly this, yes.
I've been carrying my lens like this with no problem at all since October '18 when I bought it second-hand.
The assembly usually hangs on my left shoulder with the camera hanging upside down under my arm.
I simply take a grip of the tripod mount with my left hand and lift the camera into position as needed.
The strap I'm using is a "new old stock" Pentax Deluxe SLR Camera Strap Code No. 50010 which is 40mm wide and "long enough for the job"
The only possible downside is that it's very inconvenient to also have a strap fitted to the camera body for use with "normal" lenses, so arrangements have to be made to suit.

[UncleVanya]

The only possible downside is that it's very inconvenient to also have a strap fitted to the camera body for use with "normal" lenses, so arrangements have to be made to suit.

This is where a quick release strap system really shines. I use peak design and while my lenses are not this large I do setup a set of connectors on the lens sometimes to carry the gear that way. Then I move the strap from the camera to the lens foot.

[mikesbike]

Forgive me for correcting the typos in your quoted post.
135 grams is hardly a deal breaker.
The size difference is real though, especially if you want 67 mm versus 77 mm filter threads. But with the DA*300 (which is officially a full frame lens, by the way) you get AW weather sealing, silent AF, and quick shift.
Horses for courses.

Certainly true regarding the WR and quiet AF, but not about AF speed. I have the FA* version which as I recall was designed to be even lighter and more compact than the previous "F*" version (same optically) hence the omission of the tripod mount on the FA*. AF speed is very fast and sure with my KP, with which I usually use the battery grip when using this lens, and very good too as I recall on my K-5 IIs, but it has been a while since I've used it on that camera. I also have the DA* 200mm f/2.8 SDM, similar technology to the DA* 300mm f/4, and can assuredly report its AF to be slower.

Another thing regarding quick-shift, which the FA* indeed does not feature- but its AF/MF switch is very conveniently located by the thumb while holding in the shooting position, so that becomes a moot point in practice from my own experience. And this control is instant, not requiring simultaneous switching on the camera body as well. From what I've read, this was an upgrade over the "F" version, which does require switching on both camera and lens.

[wadge22]

Certainly true regarding the WR and quiet AF, but not about AF speed. I have the FA* version which as I recall was designed to be even lighter and more compact than the previous "F*" version (same optically) hence the omission of the tripod mount on the FA*. AF speed is very fast and sure with my KP, with which I usually use the battery grip when using this lens, and very good too as I recall on my K-5 IIs, but it has been a while since I've used it on that camera. I also have the DA* 200mm f/2.8 SDM, similar technology to the DA* 300mm f/4, and can assuredly report its AF to be slower.Another thing regarding quick-shift, which the FA* indeed does not feature- but its AF/MF switch is very conveniently located by the thumb while holding in the shooting position, so that becomes a moot point in practice from my own experience. And this control is instant, not requiring simultaneous switching on the camera body as well. From what I've read, this was an upgrade over the "F" version, which does require switching on both camera and lens.

Per the info in the review database, the F* is lighter but 'fatter' (880g w/ built in hood but w/o foot, 84mm od), whereas the FA* is heavier but 'skinnier' (1067g w/ hood, 72.5mm od). They are listed as the same length.
I'm curious if that diameter is with the hood or not for the FA*. Anyone have FA* 300 with a hood, and also have a pair of calipers, that they can settle that?

I have the F* and the DA* 300, and between my copies the F* is definitely faster to focus. I think the state of the SDM in a given DA* copy will affect how fast it is, tho.
My F* also seems more able to find focus in low light, or when paired with my Rokunar 1.7x PzAF TC, which more or less doesn't work for AF with my DA* in any light, whereas it's pretty good on my F* (despite the f4.5). I'm hoping screwdrive conversion on my DA* will remedy this issue for me.

Doesn't the FA* use the "slide the focus ring forward or back" mechanism to switch between AF and MF, not a switch near the thumb? I have FA* 200 and that's how that one works (unless I'm remembering wrong, it's not used too often). You're spot on about the F* requiring switching both the lens and the camera, though, which is a real pain. Whereas the FA* (at least my 200) can have the camera left in AF all the time and just use the lens to determine AF/MF. I still believe quick shift is a fair amount nicer, though.

[straton]

I have found the Vivitar 100-500 F/5.6-8 A Series 1 lens to be sharper than the Sigma 170-500 in the foreground and as good at infinity on the K-1ii. The Vivitar is way lighter and smaller. With lenses of this era, one normally stops down two stops from wide open for the best balance between depth of field and diffraction, and indeed f/11 seems to be the sweet spot, with usable results at f/16 and f/22 when depth of field matters more.

[UncleVanya]

Anyone have FA* 300 with a hood, and also have a pair of calipers, that they can settle that?

I can try later today. I may have to use a ruler. Calipers are somewhere but I’m not sure where.

I have the F* and the DA* 300, and between my copies the F* is definitely faster to focus. I think the state of the SDM in a given DA* copy will affect how fast it is, tho.

Agreed.

My F* also seems more able to find focus in low light, or when paired with my Rokunar 1.7x PzAF TC, which more or less doesn't work for AF with my DA* in any light, whereas it's pretty good on my F* (despite the f4.5). I'm hoping screwdrive conversion on my DA* will remedy this issue for me.

Screwdrive is faster than weak sdm but when working well sdm seems to be as fast. But honestly it’s a bit subjective.

Doesn't the FA* use the "slide the focus ring forward or back" mechanism to switch between AF and MF, not a switch near the thumb? I

Yes. I think the op may be saying that on the fa* you can just switch to manual on the body but that doesn’t sound right. I can test later.

[UncleVanya]

OK I have measured & tested:

WIDTH: Nearly 3.5" is the outside width of the hood at the rubber coated end (I think it was 1/16th of an inch shy). The lens is pretty much exactly 2.75" wide at the filter ring.

FOCUS: You cannot focus the lens manually except by pulling the focusing ring towards the camera moving it out of autofocus mode. There is no "thumb" action needed. As mentioned in another post there is no requirement to flip the body switch to manual focus. if you leave the body on AF and the lens on MF you get focus confirmation (and can use catch in focus) like all other AF lenses with switches.

[wadge22]

Thank you for that @UncleVanya. Sounds like the hood diameter is 87mm to 89mm on the FA* 300mm. I did confirm on mine that the F* hood rubber bumper thing (the largest diameter part of the lens) is 84mm just as the review entry says.
So I'm going ahead and declaring that the FA*, if you include its hood, is a little larger and heavier than the F* with its non-removable hood. I suspected as much, because that F* lens is just so danged compact.
Anyhow, we're just talking about 3-5mm and 187g, so not very large a difference at all. I think the superior focus selection mechanism of the FA* would probably more than make up for the tiny difference in size/weight, if I were doing it all over again.

Sorry, all, for the mild threadjack.

[mikesbike]

Doesn't the FA* use the "slide the focus ring forward or back" mechanism to switch between AF and MF, not a switch near the thumb?

Yes, I was going by memory and had it confused with my DA* 50-135mm which has the near thumb switch. But it is still very fast, conveniently effective and does not require simultaneous switching on the body, then just as is the case with the switch by the thumb, negates the need for the quick-shift feature. In fact, in not needing an actual switch, it can be changed back and forth without your thumb even needing to be exactly at a particular place. I've found this lens handles quite well, and it is still more compact than the DA* version. The DA* version's main advantage is in its WR construction.

[Wheatridger]

You already received some good advice. Let me share a different experience.
If weight is an issue, I would recommend you to consider the FA*300mm f4.5. It is as good as the DA*300mm IMHO, FF an llighter. You can use the DA TC 1.4x to increase its range, again a fraction of the weight.
I have used very successfully this combo FA*300mmf4.5 + TC DA14.x, giving me 300 mm or 420mm at ease.
I hope that the comment may help.

I tested the two side by side and found a lot of purple fringing on specular highlights, which didn't show at all in the same photo with the DA*300.