[audiobomber]

Without knowing WHY the 55-300 isn't pleasing you, it's hard to answer your question. If it's a matter of IQ, then I doubt the Sigmas will impress you a lot. The DA* will. If it's a matter of reach, then you might be better off buying a camera with more resolution (depending on your current body) and crop. But the Sigmas WILL give you more reach.

Good summary.

I am not satisfied with the resolution of the DA 55-300mm, nor was I satisfied with the resolution of the Sigma 150-500 HSM OS. I am totally satisfied with the resolution of the DA*300mm, even with my Kenko PZ 1.5X TC attached. Unfortunately, AF with the Kenko is unreliable on my DSLR's, but works fine with my K-01. I have high hopes that we will see the roadmapped Pentax TC soon. I intend to buy a 24mp K-3 when available, for harder cropping.

I often shoot the DA*300 at f4, because in the northern Ontario woods, and in the evenings, light intensity is low. Having 300mm @ f4 and 420mm @ f5.6 works for me.

My personal opinion is that, as much as I like primes, for tele I could never work with only a prime, so I went with the 60-250. Best decision I took in a while.

I considered the 60-250 for a long time. In the end I decided on the 300mm for two reasons. With a long tele lens, I often alternate between close-ups (dragonflies, butterflies, flowers, etc) and very long shots. The prime has much better close focus ability. This was more important to my style of shooting than the ability to zoom out. Normally, I have a second body with me when shooting long.

Secondly, the prime is a longer lens. It's not just that 300mm is longer than 250mm, but also because the zoom loses more range at distances below infinity due to internal focus. When you add a TC, these effects are compounded. The 60-250 is a great lens, but I decided the prime was best for my uses.

[stormtech]

But how good of IQ will they have?

Most of these super zoom bridge cameras have a 1/2,3" sensor - quite a difference compared to APS-C.

[lesmore49]

I used my Pentax 55-300 as my wildlife lens since June 2008. It's been very good, but there have been times when I wished I had more reach.

A couple of months ago I was photographing Great Grey Owls with the 55-300 and at that point decided I needed more reach .

I have considered the DA 300 for a number of years. From all I've heard the quality is beyond reproach....but it has no further focal length than my 55-300. BTW, I bought one of the very first 55-300's and the photo quality has always been excellent....it's very sharp.

I couldn't think what the DA 300 would really offer me except three times the cost and no increase in focal length.

I tried a Pentax mount, Sigma 150-500 at a photo dealer and I was very impressed. I ordered one, when they were on sale.

It's very sharp....an excellent lens. Heavy though and I set the F stop to F 8 -F 11, ISO at 800 and the shutter speed in bright sunlight is generally around 1/1000th to 1/1600th or so. Photo's are excellent.

I thought of the Sigma 50-500, but when I'm using a telephoto....I find the 150-500 range far more useful than a 50-500 range....the 50-500 is also pricier.

So far I'm very happy with the 150-500 and plan to take it on a trip through Montana, Wyoming, North and South Dakota.

BTW....I have a K-5, Km, K10D....but so far only use it on the K-5.

[Kerrowdown]

I’ve convinced myself I need a long lens

We're all here to agree with you and help you spend your money!

[slip]

I think I would go for a *60-250 f4 with a good Teleconverter and sell the 55-300. If your grandchildren are typical, you will want something to swing up fast... A bigma would be quite the workout

Just an opinion

[davidreilly3207]

Why not rent the DA*300. You can get it at Cameralensrentals.com-Pentax Telephoto for 55.00 for 3 days or 59.00 for four and give it a good tryout. They also have both Sigmas you mentioned in Pentax mounts.