I was reading a forum post the other day about the unreliability of he SDM lenses, e.g. DA*50-135 and DA*16-50. One of the things most often said about these lenses is that they 'need to be used often' and if they haven't been used for a long period of time they won't 'wake up'.

Now, I used to take this with a pinch of salt, not having any decent logic to understand it, but recently I experienced this with my 50-135. I had not used it for approx. 6 months, then mounted it on my K-3 and tried to autofocus. Guess what? Nothing happened. I left it a short while (still on the camera), twisted the focus ring a few times and tried again. Guess what? It focussed. Since then, it appears OK, although I haven't used it much.

What can explain this? Has anyone heard about the capacitor that is apparently in the lens electronics? A capacitor, like a battery, stores electricity. It is prone to leaking that electricity over a period of time, i.e. discharging. If the SDM motor relies on smooth power delivery from the capacitor in order to make it focus, could this explain why an SDM lens won't immediately wake up if it hasn't been used for a while? Could this be why it worked when the lens had been on the camera a few minutes, because the capacitor was by then fully charged?

I don't know the answer, but it begs another question in my mind. Many of us (not me just yet) have had SDM motors replaced. Could it be that the motor was not / is not the issue? Could it be capacitors causing the problems? I know from experience with other electrical equipment that some capacitors can be prone to failure in some circuits.

This is pure conjecture, but I would be interested to know what others think, especially if there's anyone on here who understands the circuit design on the SDM lenses.

I'm sure you all won't be shy in giving your thoughts on this!

Regards
David

All the even numbers for me, 2, 4 and 6!

I particularly like the second one, not sure why, I think it might be the geometrics of the tiles and the metal grille.

Regards
David

Gorgeous image, love the way the smaller bloom recedes into the background.

Regards
David

I do agree Nigel. I wouldn't go on a trip of any length without my 55-300 - it is so valuable in lots of situations that arise when you need that extra reach. However, I'm in a bit of a dilemma as my chosen approach used to be to carry 2 DSLR's, one of which always had the 55-300 attached. I now don't want to carry 2, so I suppose lens changes are the order of the day!

55-300 is a great lens though, so much image quality for not much money. Here's one of my favourites taken with this lens:




That was with the K-5, but the K50 is well capable of similar.

Regards
David

My strongest recommendation would be to go out on a shoot with some people familiar with getting the best from Pentax DSLR's.. Whereabouts in the UK are you located GBR?

Also, I would caution against taking too much notice of what you read in the magazines! There is nothing wrong with the 18-55 lens, it is a fine optic for what it is. 18-55 is a typical reach for a 'standard zoom' lens, if you need to go longer there are plenty of alternatives available, the 55-300 being one of those. If you're looking for just a bit of extra reach and not the full telephoto of the 55-300, the 18-135 is probably a better bet, giving you coverage all the way from wide angle to short telephoto.

With a small amount of guidance, a bit of confidence and a very small amount of post processing in any of the programs available for this purpose, there is no doubt the results from your K50 will be hugely better than anything you can get from your Panasonic compact. The K50 is in a different league when it comes to image quality.

Don't be afraid to seek out someone local to you that frequents this forum, if you let us know your location I'm sure the offers of help will come flooding in.

Regards
David

Colour for me too.

Regards
David

These are fine shots Gareth, the lens has done a great job when it was behaving itself!

These are very reminiscent of Shaun Wilson's shots of lions, i.e. beautifully rendered with dark backgrounds and frame-filling subjects. The detail, colour and contrast are superb and the exposure is spot on.

I like the whole set.

Regards
David

Cheers Nigel

Regarding the issue with the lens, it seems to me that this is an actual fault with either the lens or the camera body. My suggestion would be to find someone with a Pentax camera and try the lens on a different body, this will rule out either the camera or the lens as being the cause. I once went on a nature shoot with a fellow Pentaxian who had a similar issue and we were able to confirm his problem as a camera fault by swapping lenses between our two camera bodies.

However, as mentioned earlier, the K-5 series are more prone to hunting than the K-3 bodies onwards.

Regards
David

I've done a screenshot, please see below for where to click when uploading images to a Forum thread:




Regards
David

The 55-300 is a great lens, but unfortunately it is totally unsuitable for birds in flight. Of all my AF lenses, this one hunts more than any of them. I would agree with NeilP that the DA*300 is the best for this type of work, but appreciate this is out of the price range.

Regards
David