Terrible results using Pentax DA 40 2.8 XS

Started Feb 12, 2019 | Discussions
miles green
miles green Veteran Member • Posts: 7,657
Re: In this....

Robertj_298 wrote:

miles green wrote:

Imho, a defective lens AND some motion blur...

I believe you are correct. Here is the shot with better lighting. Center laft and right crop

Yes, now at least the centre looks OK, but the edges show some decentering.

I'm assuming Pentax service would charge an arm and a leg.

However, I suspect that someone who can service film era lenses wouldn't have much trouble with this one. The construction of this lens is quite simple, with no motors inside, the optical formula can't be too complicated either.

If all else fails, think of it as a "toy lomo lens", it might make a fun soft-focus portrait lens.

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Miles Green
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Zvonimir Tosic
Zvonimir Tosic Veteran Member • Posts: 3,133
Your shutter speed ...

Robertj_298 wrote:

This was reviewed to be a good sharp lens for the $ but mine is quite bad especially at the edges. My DA 16-45 blows it away in the sharpness department. I'm wondering if I have a bad copy or is this just not a very good lens?

.. better say exposure time, is only 1/15 of a second.

So of course it blurs.

Decrease exposure time to at least 1/80 sec, and then compare the results.

Mako2011
MOD Mako2011 Forum Pro • Posts: 27,098
Not needed...
1

Zvonimir Tosic wrote:

Robertj_298 wrote:

This was reviewed to be a good sharp lens for the $ but mine is quite bad especially at the edges. My DA 16-45 blows it away in the sharpness department. I'm wondering if I have a bad copy or is this just not a very good lens?

.. better say exposure time, is only 1/15 of a second.

So of course it blurs.

But the blur (likely related to focus not motion) is not uniform across the whole frame

Decrease exposure time to at least 1/80 sec, and then compare the results.

Not not needed in this case as the issue is with the inconsistencies across the frame. And the setup may not have been handheld and the building doesn't appear to be moving

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OP Robertj_298 Senior Member • Posts: 1,357
Re: Your shutter speed ...

Zvonimir Tosic wrote:

Robertj_298 wrote:

This was reviewed to be a good sharp lens for the $ but mine is quite bad especially at the edges. My DA 16-45 blows it away in the sharpness department. I'm wondering if I have a bad copy or is this just not a very good lens?

.. better say exposure time, is only 1/15 of a second.

So of course it blurs.

Decrease exposure time to at least 1/80 sec, and then compare the results.

You must not have seem my second set of photos in the thread.

Tatouzou
Tatouzou Senior Member • Posts: 2,034
Re: Terrible results using Pentax DA 40 2.8 XS

I had the same issue with my first sample of this lens: sharp in the center and on the right but unable to get a sharp picture in the left side at aperture wider than f8.

I tried to adjust the PDAF, it did not work; then I realized that the same issue also happened in live view.

Happily, the lens, bought new in 2016 through Amazon market place was still under legal guarantee when I discovered the issue, and I got it replaced for free.

The second sample I got then is one of my best loved lens, sharp, lots of contrast even fully open (almost like the DA15), and so tiny, it is always in my bag when I use my K3 for travel, as a complement to the go-everywhere DA18-135 and the so nice DA15 limited.

IMO, it is not worth to send this lens to an official Pentax facility, they would charge you more than the price to buy a second hand working sample.

I suggest you rather to look for a local service station where some photo enthusiast tech can repair legacy mechanical lenses (any brand): it was not easy to find one where I live in Toulouse, France, but I finally did, and I got two classic Pentax lenses serviced this way for €70 each, a DA70 f2.4 with stuck aperture blades, and a F135 f2.8 which defective AF.

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Zvonimir Tosic
Zvonimir Tosic Veteran Member • Posts: 3,133
Re: Your shutter speed ...

Robertj_298 wrote:

Zvonimir Tosic wrote:

Robertj_298 wrote:

This was reviewed to be a good sharp lens for the $ but mine is quite bad especially at the edges. My DA 16-45 blows it away in the sharpness department. I'm wondering if I have a bad copy or is this just not a very good lens?

.. better say exposure time, is only 1/15 of a second.

So of course it blurs.

Decrease exposure time to at least 1/80 sec, and then compare the results.

You must not have seem my second set of photos in the thread.

I'll take another look. Thank you.

However, I can testify that regular DA40 Ltd is a fantastic lens, and well worth having. I strongly suggest you get an Ltd version instead of 40mm XS.

Richard Murdey
Richard Murdey Senior Member • Posts: 2,992
Re: Terrible results using Pentax DA 40 2.8 XS

Just post the full image next time. So much easier to diagnose.

From what I can see, classic decentering. Lens got dropped or bashed, the glass elements are no longer on axis with the sensor.

Symptoms: uneven haze/blur worse in certain areas of the frame.

My Nikon 1 10mm went the same way after my daughter dropped it...

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OP Robertj_298 Senior Member • Posts: 1,357
Re: Terrible results using Pentax DA 40 2.8 XS

Richard Murdey wrote:

Just post the full image next time. So much easier to diagnose.

From what I can see, classic decentering. Lens got dropped or bashed, the glass elements are no longer on axis with the sensor.

Symptoms: uneven haze/blur worse in certain areas of the frame.

My Nikon 1 10mm went the same way after my daughter dropped it...

Never been dropped. Hardly been used

MightyMike Forum Pro • Posts: 40,764
Re: Terrible results using Pentax DA 40 2.8 XS

Robertj_298 wrote:

Richard Murdey wrote:

Just post the full image next time. So much easier to diagnose.

From what I can see, classic decentering. Lens got dropped or bashed, the glass elements are no longer on axis with the sensor.

Symptoms: uneven haze/blur worse in certain areas of the frame.

My Nikon 1 10mm went the same way after my daughter dropped it...

Never been dropped. Hardly been used

It easily could have happened before it was in your possession.

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Pontoneer Veteran Member • Posts: 3,134
Re: Terrible results using Pentax DA 40 2.8 XS

Robertj_298 wrote:

Here is a 100% center crop and a 100 edge crop

I don’t have the XS , but I do have the DA 40mm Ltd , which I believe is optically similar , and mine is nothing like that .

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With kind regards
Derek.

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Model Mike Veteran Member • Posts: 3,895
Re: Your shutter speed ...
1

Zvonimir Tosic wrote:

However, I can testify that regular DA40 Ltd is a fantastic lens, and well worth having. I strongly suggest you get an Ltd version instead of 40mm XS.

Can't agree. I got rid of mine. Despite being delightfully small, with good IQ, it ended up gathering dust. 40mm is too long for street or landscape photography, and too wide for portraiture. It's no coincidence that most manufacturers ignore this FL.

The 21 and 70 are marginally more useful, though I long ago got rid of my 21 in favour of a Ricoh GR which has a sharper lens and more accurate focusing.

The 70 is a gorgeous portrait lens, but requires agile and accurate AF especially when shooting wide open. A lens which can reap rewards, but is demanding of the photographer. It reallly needs a mirrorless body.

The Ltd's were a great selling point in their time but not sure that they would swing me towards Pentax now.

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Tatouzou
Tatouzou Senior Member • Posts: 2,034
Re: Your shutter speed ...

Model Mike wrote:

Zvonimir Tosic wrote:

However, I can testify that regular DA40 Ltd is a fantastic lens, and well worth having. I strongly suggest you get an Ltd version instead of 40mm XS.

Can't agree. I got rid of mine. Despite being delightfully small, with good IQ, it ended up gathering dust. 40mm is too long for street or landscape photography, and too wide for portraiture. It's no coincidence that most manufacturers ignore this FL.

The 21 and 70 are marginally more useful, though I long ago got rid of my 21 in favour of a Ricoh GR which has a sharper lens and more accurate focusing.

The 70 is a gorgeous portrait lens, but requires agile and accurate AF especially when shooting wide open. A lens which can reap rewards, but is demanding of the photographer. It reallly needs a mirrorless body.

The Ltd's were a great selling point in their time but not sure that they would swing me towards Pentax now.

YMMV: I have the 21, the 40 and the 70.

The 70 delivers very pleasing portraits with a pleasing bokeh, but 105 mm FF equivalent is telephoto designed for subject isolation or perspective compression, and thus often too narrow for many scenes.

21 is moderate wide angle, very close to the angle of view of smartphone cameras. Some like it, other dont (too narrow or too wide).

40 is 60MM FF equivalent, a little longer than the "standard" 50mm FF equivalent (which would be 33mm in APS-C). Some may consider it too narrow compared for instance to the 35mm primes (the f2.4 plastic wonder or the stunning f2.8 macro limited). But, as for me, I like it.

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Richard Murdey
Richard Murdey Senior Member • Posts: 2,992
Re: Your shutter speed ...

Tatouzou wrote:

YMMV: I have the 21, the 40 and the 70.

The 70 delivers very pleasing portraits with a pleasing bokeh, but 105 mm FF equivalent is telephoto designed for subject isolation or perspective compression, and thus often too narrow for many scenes.

21 is moderate wide angle, very close to the angle of view of smartphone cameras. Some like it, other dont (too narrow or too wide).

40 is 60MM FF equivalent, a little longer than the "standard" 50mm FF equivalent ... But, as for me, I like it.

70->105mm is a short tele. Not as short as an 85mm, but pretty near.

21->is 31mm, mid way between 28mm and 35mm and the same FOV as the FA31mm on FF.

40->60mm is about 58mm, i.e. what was considered a standard lens before technology improved and standard lenses became 50mm as people wanted. But you do you, as the kids say these days.

Ultimately the principle downside with all these DA limiteds is not the focal length, however, its their slow (equivalent) aperture. A 58mm F1.4 is far more flexible than a 60mm F4 and-not-even-a-frikin'-macro.

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alex_virt Senior Member • Posts: 2,105
Re: Terrible results using Pentax DA 40 2.8 XS
1

I've had bad experience with this lens too. Not this bad, but still not good. No matter how I tried to adjust the AF, I couldn't get good sharpness across the frame. Either the centre was sharp and the edges were blurry or vice versa. Returned it and bought the DA 50/1.8 instead – MUCH better!

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