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Pushed too far

PostPosted: Tue Sep 18, 2018 12:56 pm
by Sparkie67
Hi, whilst away on the Isle if Arran had the fortune to spot some birds of prey.
I have the K3II and had the 55-300 zoom fitted. The overall picture is poor in my opinion.
Overcast day with light rain. Aperture wide open and at full zoom. Had spot focus on which was fun aiming for a small fit in the viewfinder. ISO was at 3200 and 6400 to try and maintain a good shutter speed.
Got them on the computer to try and enlarge them and the subject is either grainy or out of focus. Maybe a higher ISO to increase shutter speed again but then the grain creeps in when increasing image on PC.
Just wondering if anyone has used the Pentax teleconverter rather than buy an oversize lens.
Was thinking of swapping to the sigma 18-270 and the 1.4x adapter which would cover just about every eventuality needed.
Spotted an eagle earlier and managed to shoot a few with the 18-50 lens but he flew off before I could swap lenses.
Any advice for future would be appreciated.

Pushed too far

PostPosted: Tue Sep 18, 2018 11:23 pm
by Smeggypants
Watcha :)

Have you adjusted the autofocus fien adjustment for that lens. First thing I'd check. :)

Regards Shutter speed and ISO, I'm all for upping the ISO to maintain a fast enoguh shutter speed. Grain can be reduced with decent Noise reduction, but camera shake/motion blur is nigh on impossible to reduce

Pushed too far

PostPosted: Wed Sep 19, 2018 6:01 am
by richandfleur
What mode were you on?

There's a setting for ISO auto behaviour, and I've set mine to fast. That instructs the camera to do just what you're after, in terms of targeting a faster shutter speed with high ISO, rather than trying to keep ISO low to keep noise down and with a slower shutter speed.

That, plus AF fine tuning is about all you can do, before having to opt for a much more expensive/longer reach/wider aperture lens.

Re: Pushed too far

PostPosted: Wed Sep 19, 2018 12:01 pm
by Sparkie67
Thanks for the replies, I was using manual mode with single spot focus.
With reference to fine auto focus, can someone explain more please. Is it an extra setting i’ve missed in the camera.
Maybe better in future to set shutter priority and let camera do the rest.
Still looking at the Sigma lens as an allone option for close and tele use if anyone has experience of it.
Thanks
Andy

Pushed too far

PostPosted: Wed Sep 19, 2018 8:42 pm
by richandfleur
Rather depends if your soft images are due to motion blur (shutter speed too long to freeze motion) or missed focus.

Each lense autofocus settings can be calibrated to the camera, and often this can improve the focus accuracy.

Frankly all in one lenses are usually fairly average. It costs a lot to go really wide or really long and that’s just the way it is. I think the Pentax 55-300 is the best of the cheaper all in ones.

Re: Pushed too far

PostPosted: Thu Sep 20, 2018 2:23 am
by Smeggypants
Sparkie67 wrote:Thanks for the replies, I was using manual mode with single spot focus.
With reference to fine auto focus, can someone explain more please. Is it an extra setting i’ve missed in the camera.
Maybe better in future to set shutter priority and let camera do the rest.
Still looking at the Sigma lens as an allone option for close and tele use if anyone has experience of it.
Thanks
Andy




In the K-5 it's in the custom menu [#26. AF Fine Adjustment]. I don't have a K-3 but I suspect it's somewhere similar. Basically you take a series of test shots wide open for narrowest DOF on a subject that allows you too see if the lens is front of back focussing and adjust until your target is in focus. This can change with subject distance so best to check with a focal distance that you mainly use the lens for.

I've had some lenses that seriously back or front focus which I've had to correct with this parameter.

Pushed too far

PostPosted: Thu Sep 20, 2018 7:05 am
by MrB
Having never shot distant wildlife I cannot help in that respect. However, there are some general points arising from your first post:

"I have the K3II and had the 55-300 zoom fitted.....Overcast day with light rain."
If you were you shooting in the rain, do you have the WR version of the 55-300? I doubt that the Sigma 18-270 will be weather-resistant. Also, if it was raining and your subject was far away, there will have been a huge number of obstructions (i.e. raindrops) affecting image quality.

"Aperture wide open and at full zoom."
Lenses are usually nowhere near their best at their extremes.

"ISO was at 3200 and 6400 to try and maintain a good shutter speed."
Obviously there will be more grain (noise) at higher ISO values and noise reduction will reduce detail in the image.

"Got them on the computer to try and enlarge them and the subject is either grainy or out of focus."
Do you mean cropping the image to increase the size of the subject within the frame? If so, you will also be accentuating any graininess or softness introduced when the image was shot.

"Was thinking of swapping to the sigma 18-270 and the 1.4x adapter which would cover just about every eventuality needed."
Adding the converter will not help image quality, as there are several extra glass surfaces that will degrade the image. Also it will cause a reduction of light by one stop, so you will either have to further increase ISO or reduce shutter speed, potentially exacerbating the problem.

Philip

Re: Pushed too far

PostPosted: Fri Sep 21, 2018 2:58 pm
by Sparkie67
Thanks again for the replies.
Will look for the fine AF adjustment.
Sounds like I need to either get nearer the subject, wasn’t easy at all. Maybe invest in a bigger lens in the near future.
I know it’s never easy when an opportunity arrives, and you just have to go with what you have got. And maybe more practise at getting the correct settings.
The Pentax is the WR version, and see your point about the Sigma maybe not having weather protection.

Many thanks
Andy

Pushed too far

PostPosted: Thu Jul 25, 2019 8:41 am
by oldjoe
not sure there is a Sigma 18-270, there are Tamron and Pentax lenses in that range. the same lens i think but the Pentax has different coatings i believe. however these are "consumer" lenses and none are very good when operated at their max range. you would be better moving up to something better, Sigma 50-500, Sigma 150-500 or even the older Sigma 170-500 on from that would be Pentax DA*300 f4 or Pentax 150-450 but you are into serious money with those compared to the others. also the Sigma's are very heavy so unless you have rock steady hands you would need support for the camera. just my two pennies worth