Sigma APO 75-300mm f4.5-5.6

marcusBMG · Joined: 07 Dec 2012 Posts: 1305 Location: Conwy N Wales

There is a proliferation of sigma 70/75-300mm super telephoto zooms: MF initially and then AF versions. I have no idea as to the precise place of this one in the general scheme of things, Pentax Forums lens reviews lists 7, including a listing for a 75-300mm DL which looks very similar to this and is well rated.

This was boxed with case, excellent overall condition, but described as having some haze/dirt on the front element. Proved to be a funny sort of whitish haze that wouldn't come off - it's highlighted by flash in the pic below. Perhaps age related coating deterioration? Then I noticed more haze: an element in the second group afflicted with spotting suggestive of condensation from lubricants, and a misty element further back. That I am sure is the one most responsible for causing some fogging/flare.

So that's two duff sigmas in one week!
However pics show the lens has potential... jpg's, Pentax K5. With an eye on the direction of the light significant fogging of the pics was avoided.

300mm, close focus (I think I was a bit off the max 1:4)

Crop:

200mm odd if I remember right, f8

135mm f8

Sparrow chasing - 300mm- Samsung NX20, pp'ed and exported from RAW in LR3.6 . Big crop to ~1500px, then resized.

These were showing the effects of the haze - ameliorated in LR mainly by bumping blacks. Without:

buerokratiehasser · Joined: 12 Jun 2011 Posts: 470

Try vodka or stronger.

Not sure this will help the haze. I had a similar 70-210/4-5.6 and never got a tack sharp shot with it. It had the resolution but it was just no fun. Similar to a mirror lens without the donuts.

marcusBMG · Joined: 07 Dec 2012 Posts: 1305 Location: Conwy N Wales

I was trying acetone - pretty sure that would have shifted anything shiftable. I am wary of putting too much elbow grease into rubbbing because of the risk of taking off the coating.
Doesn't look like an easy lens to get into either - front element retaining ring doesn't have slots for my lens spanner.

mikeyp163 · Joined: 22 May 2017 Posts: 1

I have one of these lenses in MD fit. When I got it it had apparently bad case of fungus. As I had paid peanuts for it I decided to chance it and took it apart. This was a couple of years ago. I recall it was a simple job to get it apart as it is built in a surprisingly logical way compared with some. I cleaned it up and got it back together again without great difficulty. The only difficult bit was getting the front element seated correctly in the thread to be able to get infinity focus - I forgot to mark the threads.
I think I got the front element out by twisting it with the rubber end off my grand-daughter's bow and arrow set!!! It's just screwed in if I remember correctly.
Since I cleaned it I have been very impressed with it's performance. Very sharp, smooth focus and zoom, nice balance.
#1

DigiChromeEd · Joined: 29 Dec 2009 Posts: 3462 Location: Northern Ireland

TrueLoveOne · Expire: 2013-12-24

marcusBMG · Joined: 07 Dec 2012 Posts: 1305 Location: Conwy N Wales

Aye well, encouraged by mikeyp indication that this lens might not be so difficult to work on, it's in the project box and I hope to update this thread as and when..

iangreenhalgh1 · Expire: 2014-01-07

I have the red band AF version, which is the first of several AF versions and it's a good lens, not upto the standards of things like the Minolta AF 70-210 beercan but still good enough for most work. It's not great at 300mm, but upto 250mm it's not bad at all on my a850.

buerokratiehasser · Joined: 12 Jun 2011 Posts: 470

Got a temporary caffeine fix so I am just dropping in to add another irrelevant yarn.:

See that DOF graph on the body? There is at least one lens that has very curvy DOF graphs, some people could even say pleasant to look at.

It is the Sigma 28-200 and I think the weird lines come from the fact that it is a turn-zoom. Pretty thick pipe, metal.

Optically it is so-so. It is not something you would take for bird hunting but it did surprisingly good for an old super-zoom. If it is darker than daylight you got to use ISO 200, 400 anyway so the smudging is not losing too much info (APSC 10mpix)