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08-09-2015, 05:41 PM   #1
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Sigma 150-500mm APO (OS version) and Pentax K-3 - soft focus! ?

Hello all,

I recently purchased this lens and had high hopes for finally owning a decent long lens after a few years.

Unfortunately, my first test photos were less than overwhelming. Despite testing MF and AF camera settings, a reasonably fast shutter speed (+ 1/1000), small apertures of more than f8, zoom testing from 150mm to 500mm, on tripod, testing all the lens settings such as OS OFF, 1, 2, and the AF SETTING ON/OFF I cannot capture a sharp image... all images are somewhat soft. BTW, the camera is in single spot focus and the focused indicator activates, as well, through the lens, the images do appear focused.

Yes, the auto-focus is working. Yes, the camera is working.

What can I possibly look at in order to determine the cause?

Even my old manual focus Tameron 500mm catadioptric lens yields much sharper images. Glad I brought that lens with me!

Very sad and disappointed!

Sorry, I cannot show examples because I am on vacation and without a method to transfer images to my iPad.

Thank you for your advice !
Shawn

08-09-2015, 05:49 PM   #2
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Have you tried using Live View focus?

I guess I'm lucky that none of my cameras or lenses have ever had to be adjusted for focus...
08-09-2015, 06:38 PM   #3
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Try live view on a really stable tripod using a remote, with a very well lit subject so you have a fast shutter speed, with all types of stabilization and shake reduction turned off completely.

Is it in reasonably sharp focus?

No? Sounds like your lens has a problem.

Yes? Then rack it out of focus and switch live view off, autofocus again, take the photo again.

Is it in sharp focus? No? Try again a couple more times. Still no? it needs AF fine tuning. (or it might need mirror lockup, so try that first I guess)

Yes? Try adjusting the lighting and shutter speed, aperture, etc. Maybe your tripod isn't stable enough for slower shutter speeds at the focal length in question, or you're not using a remote so it's getting some shake from your hands, or ... something else.
08-09-2015, 06:50 PM   #4
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One other thing that will help with the longer end. Turn off the in camera IS because it will fight the OS.

08-09-2015, 07:55 PM - 1 Like   #5
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This is quoted from a previous Pentax forum answer I provided to another individual who was having difficulty getting sharp pix from their Sigma 150-500.

BTW, you're not alone in not getting sharp pix from the 150-500. Before I bought mine, I checked out both the Canon forum (I also have Canon equipment) and the Pentax forum. I noted that ...in both forums...some got out of focus pics, some got tack sharp pics.

I believe the issue is not with this lens, nor is it with either Canon or Pentax DSLR's. I believe it is a question of technique. It's a big, heavy, super telephoto.
A lens this size, needs careful technique to get the most out of it.

These settings and procedures work well for me, when using my Sigma 150-500.

I don't use a tripod, generally. Normally I use the Sigma 150-500 when the light is good, plenty of sun.

I use it handheld.

I find I get sharp pictures from it...yes...even at 500mm. I use it with my Pentax K-5 (with grip and extra battery) and use the Pentax shake reduction, rather than the Sigma shake reduction (OS)...although the Sigma OS works fine. Remember to shut off the OS system if you have the Pentax SR switched on. Also if using a tripod...don't use any shake reduction system...either Pentax or Sigma.

I support the lens by either holding the lens handle or holding the lens body with one hand, gripping the handle with my hand under the handle and bracing my arm against my body.

I use the other hand, to hold the K-5.

I'm an older man, but find I can handhold the body and lens ok, this way. I am 6' 3" and around 240 lbs...so maybe my size is a factor, when it comes to hand holding and supporting the K-5, Sigma combo. I don't know.

I find settings are very important for a large, heavy lens.

On my Sigma I use 800-1600 ISO, F 10, F 11 and shutter speeds over 1/1000th of a second if possible. I've used as low as around 1/350th, 1/500th...and although I've been happy with the picture...I find I'm pushing my luck if I use shutter speeds this low, on a large, heavy lens.

I use F 10, F 11, due to the fact that I find a super telephoto has minimal depth of field at F 5.6, 6.3. F 10, etc...gives me enough depth of field to get a bird the size of a flying pelican ...all in focus...wing tip from wing tip.

I use it to take pics of wildlife, wild birds...I always spot focus on the eye. If you get the eye sharp and have reasonable F stop/shutter speeds...the pix will be sharp....well so far, this works for me.

I also use it to take pix of racing cars at the drag strip. It is tack sharp here too.

What I'm saying is technique is important with any large lens....even when using a tripod. I'm sure you have both the Pentax and Sigma shake reduction switched off using a tripod. Again, with a long lens at the 500mm setting....F stop is critical for adequate depth of field.

Hopefully some of my experience is helpful.

Good luck .

Les

Read more at: https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/300721-pent...#ixzz3iNOFMwf8
08-09-2015, 08:43 PM   #6
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Original Poster
Thank you all, for your excellent suggestions.

I'll update you with what I did to improve the focus.

The first thing I'll do is get into a controlled environment where I'll test on a focus screen with a stable mount.

Thank you.
08-10-2015, 11:37 AM   #7
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LesMore's suggestions are all good. I took out my new (to me) Sigma 150-500 yesterday. I was looking for birds but few were to be found. i did however find this dragon fly and got this with a handheld effort.

I also turn off the camera IS and on this first use, used the lens OS 2 setting. I had to work on breathing and bracing the camera with my body because if not, it tends to wobble all over. The other thing to know is that the in lens OS only kicks in when you half-press the shutter and it takes about a half second to lock in. Even with all that about 1/3 of my dragon fly photos were slightly out of focus. I think it is a practice thing. I'm going to take more photos of stationary birds or objects in order to work on my technique. There are just too many variables with moving objects to know what is going on.

I need more practice for sure but got enough sharp photos to know that the lens is very capable hand held. Just need to work on my technique for stable shots with this larger lens.

08-10-2015, 11:47 AM   #8
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QuoteOriginally posted by TedW Quote
LesMore's suggestions are all good. I took out my new (to me) Sigma 150-500 yesterday. I was looking for birds but few were to be found. i did however find this dragon fly and got this with a handheld effort.

I also turn off the camera IS and on this first use, used the lens OS 2 setting. I had to work on breathing and bracing the camera with my body because if not, it tends to wobble all over. The other thing to know is that the in lens OS only kicks in when you half-press the shutter and it takes about a half second to lock in. Even with all that about 1/3 of my dragon fly photos were slightly out of focus. I think it is a practice thing. I'm going to take more photos of stationary birds or objects in order to work on my technique. There are just too many variables with moving objects to know what is going on.

I need more practice for sure but got enough sharp photos to know that the lens is very capable hand held. Just need to work on my technique for stable shots with this larger lens.

That's why all of my shooting is AF.C with the back button.

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