Lens weight and camera shake ?


PeterKR

Link Posted 13/01/2013 - 16:54
When looking for a new camera one of the reasons I chose the Pentax K-r was the in-camera Shake Reduction. I thought this would be an advantage as it meant I could use less complicated lenses that would be lighter to carry around.

When I got the twin-lens kit I was disappointed with the apparent softness of images from the DAL 18-55. Whilst the performance in bright light was good it was not good in poorer light or in close-ups of flowers.

When I got my Sigma 28-70 epsilon AF I was delighted with the sharper images I got although people commented how heavy this lens seems (it is a solid metal-bodied lens as opposed to the lightweight plastic construction of the DAL 18-55). Because of the better results this then became my 'standard' lens.

Recently, wishing to carry a lighter camera/lens combination I fitted the DAL 18-55 and took some shots which included repeats of some previously taken with the Sigma lens and was again disappointed by the results (2 shots of Mapledurham Mill have been posted on the Gallery to demonstrate this).

However, (and this now leads me to the reason for the posting), on review I noticed that the shot with the Sigma had a shutter speed of 1/250 whereas the DAL was at 1/125. This made me wonder whether the apparent 'softness' of the DAL image was actually due to 'camera shake' despite the use of the K-r's SR 'ON' ?

Basic physics tells me that heavier objects have a lower natural frequency of vibration than lighter objects.

Could this result in a lighter lens being more susceptible to camera shake than a heavy lens.

And is the Pentax SR system better able to compensate for low frequency shake than higher frequencies ?

I should add that all my shots so far have been taken 'hand held' !

John Riley says he has not experienced any problems with the Pentax 18-55 lenses but were yours heavier DA or WR versions, John ?

Any thoughts ?

Peter

gwing

Link Posted 13/01/2013 - 17:07
My guess is that differences in results between the two lenses is likely to be because of their IQ not their weight.

Yes a heavier lens should be less susceptible to movement (assuming it is not so heavy your muscles are quivering with fatigue ) but the weight difference between DA and DAL 18-55 is going to be so miniscule it'll have no measurable, let alone noticeable, effect. Remember the lenses are attached to a camera so it is the combined weights of lens and camera you need to compare.

johnriley

Link Posted 13/01/2013 - 17:22
I tested the K-r with DAL lens. I've owned two each of the DA and DA II lenses. I now have two of the WR lenses. I tested the K-II with the WR lens supplied.

All have been pretty much the same.
Best regards, John

andrewk

Link Posted 13/01/2013 - 18:36
PeterKR, it's possible that your experience (and mine) might be down to sample variation. My 18-55mm Mk2 kit lens is definitely sharper than my Sigma 28-70 epsilon AF which I now don't use - if you want another, let me know.

Andrew
Flickr photostream

Charlotte

Link Posted 13/01/2013 - 18:48
Peter,
You're not alone. I couldn't get any decently sharp photos with the kit lens that came with my Kr. I thought it was just me until I bought a cheap Pentax F 35-70 mm which is as sharp as a tack.

People rave about the wonders of the 18-55 kit lens, but I definately had a duff one, maybe it depends on which batch it came from.

Kind regards
Charlotte
Pentax Photo Gallery
Photography blog

andrewk

Link Posted 13/01/2013 - 18:57
Charlotte wrote:
I thought it was just me until I bought a cheap Pentax F 35-70 mm which is as sharp as a tack.

I have a Pentax F 35-70mm lens too and it also is as sharp as a tack. It is, though, no sharper than my 18-55mm kit lens at 35mm, f/5.6. If your kit lens is much worse, then you might indeed have a duff one.

Andrew
Flickr photostream

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milamber

Link Posted 13/01/2013 - 19:08
I've had two kit lenses - a Mk2 non WR which was excellent and a WR one which was really poor on the same camera so there must be variation in samples

PeterKR

Link Posted 13/01/2013 - 20:34
Many thanks for all your contributions - perhaps I do have a duff DAL 18-55 lens and don't have 'the shakes' after all !

This would seem to be backed up by the fact that whilst it gives reasonable results in bright light the exposure and colour rendering are also bad in poor light (which would NOT be down to camera shake).

There are bound to be variations in quality in any mass produced item - it is just sad that a 'Premium brand' like Pentax allows the bottom end to be so low !

Interestingly about a year ago I took a similar shot of The African Queen, to that posted on the Gallery today, using my other kit lens the DAL 50 -200 and THAT one WAS sharp !

So it looks like my 18-55 is going back in the box again (for emergency use only!)

Peter

stub

Link Posted 13/01/2013 - 20:59
Maybe for a small outlay you could get a second opinion, so to speak. By hiring another 18-55 lens from SRS and testing that against the one you have.
K-1Gripped K-1 ungripped K-5ii K7 Various lenses

Stuart..

andrewk

Link Posted 14/01/2013 - 15:08
We had a bit of snow this morning, so I thought I'd go for a wander. This was taken near Besom Hill in Oldham.




This is a 100% crop .......




It was taken with a Pentax K30 and 18-55mm Mk2 kit lens. The kit lens sure looks sharp enough to me.

Andrew
Flickr photostream

PeterKR

Link Posted 14/01/2013 - 22:29
andrewk wrote:
We had a bit of snow this morning, so I thought I'd go for a wander. This was taken near Besom Hill in Oldham.


Andrew

Many thanks, Andrew, for this and the other comments.

I right-clicked on the main image and it showed EXIF data of f/14 ay 1/60s so no camera shake but a stopped down lens !

You got me thinking that my problems with my DAL 18-55 may stem from when it is used opened up (i.e. f/4 or 5.6) which might explain the better results in bright light when the camera in 'P' mode would probably have stopped it down.

I therefore did a quick check on some shots taken in bright light last May and have posted one on the Gallery today. Whilst many of the flower blooms are a bit soft this is a d.o.f. issue, since I took the shot near the minimum focus distance, and some areas are pin sharp. The EXIF data shows that the lens was stopped down to f/10.

I will try some shots at f/11 using Av instead of P and see what results I get ?

Peter

johnriley

Link Posted 14/01/2013 - 22:34
Quote:
I will try some shots at f/11 using Av instead of P and see what results I get ?

Good idea, you'll get optimum performance stopped down, providing camera shake is avoided.

A tripod is always best when evaluating lenses. The 2 second delay will rauise the mirror before exposure and switch off SR, thus removing any chance of vibration or over-compensation.
Best regards, John

andrewk

Link Posted 14/01/2013 - 23:51
PeterKR wrote:
I right-clicked on the main image and it showed EXIF data of f/14 ay 1/60s so no camera shake but a stopped down lens !

The shot was taken at 18mm, so I was a lot closer to the tree than you'd think. I stopped down to try and maximise depth of field. I had intended to take the shot at f/16 not f/14 - just haven't yet got used to where the wheels are on the K30, must have nudged one unintentionally.

For this shot, I set exposure to manual with single point spot metering. I set aperture to f/16 (or so I thought) and metered off the snow - adjusting shutter speed to indicate two stops over-exposure.

Quote:
You got me thinking that my problems with my DAL 18-55 may stem from when it is used opened up (i.e. f/4 or 5.6) which might explain the better results in bright light when the camera in 'P' mode would probably have stopped it down.

If you don't need to throw the background out of focus, you'd be better off sticking to f/8 and onwards.

Quote:
I will try some shots at f/11 using Av instead of P and see what results I get ?

From f/11 on, the kit lens is as sharp as just about anything you can buy.

As an aside, I tried out the Sigma 28-70mm Epsilon this afternoon - but thoroughly cleaned all the electrical contacts first. It seems to focus a bit better than it did on the K200D. I'll try it out again in the daylight tomorrow.

Cheers
Andrew
Flickr photostream
Last Edited by andrewk on 15/01/2013 - 00:06

andrewk

Link Posted 15/01/2013 - 13:01
I spent quite some time today comparing the Sigma 28-70mm Epsilon with both the Pentax 18-55mm MK2 kit lens and also the Pentax F 35-70mm.

The Sigma focussing seems much more reliable after cleaning the contacts on the lens. Focussing seems more accurate too, at or near infinity, but it still does fail to find focus occasionally (maybe one shot in 10). When it does nail focus, at 50mm (probably it's best focal length), at f5.6, it is close to and maybe marginally better than the kit lens at the same settings (the kit lens's worst focal length). I'd need to do more testing to be sure, but that is quite encouraging.

I also compared the Sigma with the Pentax F 35-70mm at 70mm and at f/4.5, f/5.6, f/8 and f/11. Frankly, the Pentax F walks all over the Sigma. It isn't just better, it is a lot better. The Sigma is a little better at f/8 than the Pentax is wide open. The Pentax, however, is clearly sharper at f/5.6 than the Sigma at any aperture and it improves further at f/8.

The Sigma is much better than I thought it to be and at some time, I might well sell it without worrying about it. For now, though, it stays on top of the wardrobe.

Andrew
Flickr photostream

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PeterKR

Link Posted 15/01/2013 - 14:10
andrewk wrote:
I spent quite some time today comparing the Sigma 28-70mm Epsilon with both the Pentax 18-55mm MK2 kit lens and also the Pentax F 35-70mm.

Andrew

Many thanks, again, Andrew. You have done a really thorough job and I do appreciate the time you've given to this one.

Can you confirm that the 'star' lens is the Pentax 'F' (as opposed to the 'FA') 35-70 ? The 'FA' ones come up frequently on ebay but I've not seen any of the 'F' series recently ? Looking at the US Pentax Forum the FA's don't get as good reviews ?

Meanwhile, have you checked my Weigela shot on the Gallery ? This was taken with the DAL 18-55 at 42.5mm and close to minimum focus distance as a pseudo macro shot. I think that is why there are a lot of 'out of focus' leaves and blooms but those that are focussed seem quite sharp to me ?

I've not had time to do the comparitive experiments myself yet but will post results when I have them.

Peter
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