Sigma 50mm 1.4 soft?

Started Apr 21, 2013 | Discussions
Aidan Gibson
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Sigma 50mm 1.4 soft?
Apr 21, 2013

Hi there,

I bought the sigma 50 1.4 a few weeks ago and I have noticed I don't get any sharp pictures till f2.0? Is that normal or did I just get a bad copy? Could it be focusing problems? Do I have to send it in, because as you may know K-5iis only can adjust to +and - 10.

Any thoughts, can anyone help?

Cheers

 Aidan Gibson's gear list:Aidan Gibson's gear list
Pentax K-x Pentax K-5 IIs Sigma 50mm F1.4 EX DG HSM Pentax smc DA 55-300mm F4.0-5.8 ED Sigma 30mm F1.4 EX DC HSM +2 more
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Winder
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Re: Sigma 50mm 1.4 soft?
In reply to Aidan Gibson, Apr 22, 2013

I have found that AF accuracy below f/2 seems lacking.  I have some really sharp pictures at F/1.4 but it has not been as consistent as I would like.  Much better on the K-5 than it was on the K-7.

Does your LiveView work?  If not send it back to Sigma and let them update lens firmware.

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Pentax K-3 Sigma 50mm F1.4 EX DG HSM Pentax smc FA 31mm F1.8 AL Limited Sigma 85mm F1.4 EX DG HSM
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Infrabasse
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Re: Sigma 50mm 1.4 soft?
In reply to Aidan Gibson, Apr 22, 2013

I had one and could get sharp pictures but it's obviously a little tricky @ 1.4 but a bit hit and miss.

Make sure you do your tests with a static subject and with a tripod as you or your subject may be rocking slightly back and forth.

Please note you also have a global lens adjustment which cumulated with the individual lens adjustment could allow you to adjust the equivalent of -20;0 or 0;+20. Although that will probably induce issues with your other glass.

As above, It'd be interesting to know if you can get sharp pictures in live view.

Do you find the lack of sharpness is more pronounces on a specific side?

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MightyMike
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Re: Sigma 50mm 1.4 soft?
In reply to Aidan Gibson, Apr 22, 2013

no pictures so i can't say what the issue is... what about CDAF???

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awaldram
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Re: Sigma 50mm 1.4 soft?
In reply to Aidan Gibson, Apr 22, 2013

Aidan Gibson wrote:

Hi there,

I bought the sigma 50 1.4 a few weeks ago and I have noticed I don't get any sharp pictures till f2.0? Is that normal or did I just get a bad copy? Could it be focusing problems? Do I have to send it in, because as you may know K-5iis only can adjust to +and - 10.

Any thoughts, can anyone help?

When you go below the sensor native reading ability calibration is critical f`1.4 is below this level.

As Mike said without images we cant tell you anything as your softness may be related to PP or even incorrect expectation.

I take it from your comment on +-10 your not really sure what or how to calibrate your camera.?

This is the easiest and IMO most accurate method, As it caters for non 50/50 Front back focus (where most 'have a go' fail to calibrate correctly and destroy camera calibration).

Moire AF tuning

Don't forget to calibrate at an appropriate distance min 25x focal length ideal 50x focal length.

So for your lens 50mm X 25= 1.25M Min and ideally 2.5Metres.

On the subject of do I have t send it in.

You cannot send it to Pentax as they will reject the warranty repair because of the 3rd party lens so if you are 'sending' it in it will have to be to Sigma.

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Pentax Q Pentax K-3 Pentax smc DA* 55mm F1.4 SDM Pentax smc DA* 16-50mm F2.8 ED AL (IF) SDM Pentax smc DA* 50-135mm F2.8 ED (IF) SDM +11 more
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Aidan Gibson
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Re: Sigma 50mm 1.4 soft?
In reply to awaldram, Apr 22, 2013

You cannot send it to Pentax as they will reject the warranty repair because of the 3rd party lens so if you are 'sending' it in it will have to be to Sigma.

Would I have to send my camera with it?

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Pentax K-x Pentax K-5 IIs Sigma 50mm F1.4 EX DG HSM Pentax smc DA 55-300mm F4.0-5.8 ED Sigma 30mm F1.4 EX DC HSM +2 more
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Aidan Gibson
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Re: Sigma 50mm 1.4 soft?
In reply to Winder, Apr 22, 2013

Winder wrote:

I have found that AF accuracy below f/2 seems lacking.

Okay, that means it isn't just my lens.

I have some really sharp pictures at F/1.4 Does your LiveView work?

CDAF does work, pictures seem to be in focus but again pictures normally seem quite soft.

Thanks for the reply!

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Pentax K-x Pentax K-5 IIs Sigma 50mm F1.4 EX DG HSM Pentax smc DA 55-300mm F4.0-5.8 ED Sigma 30mm F1.4 EX DC HSM +2 more
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Aidan Gibson
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Re: Sigma 50mm 1.4 soft?
In reply to Infrabasse, Apr 22, 2013

I had one and could get sharp pictures but it's obviously a little tricky @ 1.4 but a bit hit and miss.

Is this because of the narrow DOF? If yes then I thought of this and that would also explain why it starts to get sharp a f2.

Make sure you do your tests with a static subject and with a tripod as you or your subject may be rocking slightly back and forth.Please note you also have a global lens adjustment which cumulated with the individual lens adjustment could allow you to adjust the equivalent of -20;0 or 0;+20. Although that will probably induce issues with your other glass.

Could you explain how I "access" this global lens adjustment? Does this mean it would stay adjusted on any lens?

As above, It'd be interesting to know if you can get sharp pictures in live view.

Again yes they are in focus but mostly pretty soft.

Do you find the lack of sharpness is more pronounces on a specific side?

Haven't noticed any sharper side.

Cheers

 Aidan Gibson's gear list:Aidan Gibson's gear list
Pentax K-x Pentax K-5 IIs Sigma 50mm F1.4 EX DG HSM Pentax smc DA 55-300mm F4.0-5.8 ED Sigma 30mm F1.4 EX DC HSM +2 more
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Aidan Gibson
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Re: Sigma 50mm 1.4 soft?
In reply to awaldram, Apr 22, 2013

I take it from your comment on +-10 your not really sure what or how to calibrate your camera.?

On my K-x I never used auto focus lenses, I got them with my IIs 4 weeks ago so no, I have no idea about calibration of the lenses/camera.

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James O'Neill
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Re: Sigma 50mm 1.4 soft?
In reply to Aidan Gibson, Apr 22, 2013

Aidan Gibson wrote:

I had one and could get sharp pictures but it's obviously a little tricky @ 1.4 but a bit hit and miss.

Is this because of the narrow DOF? If yes then I thought of this and that would also explain why it starts to get sharp a f2.

On another thread (on Pentax's 50mm being soft) I posted the sums to calculate DOF. But at 2M / 6ft D.o.F is +/- 5CM / 2"

they are in focus but mostly pretty soft.

Don't expect the maxium sharpenss from any lens at its widest apperture. My hunch is that the resolution of todays sensors allows you to see the step in softness in both Pentax and Sigma 50mms when you open up that last stop.

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Infrabasse
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Re: Sigma 50mm 1.4 soft?
In reply to Aidan Gibson, Apr 22, 2013

Aidan Gibson wrote:

I had one and could get sharp pictures but it's obviously a little tricky @ 1.4 but a bit hit and miss.

Is this because of the narrow DOF? If yes then I thought of this and that would also explain why it starts to get sharp a f2.

Yes that's what I was implying. For this I point you to my static subject + tripod advice to find out if the problem lies with the lens or technique.

Make sure you do your tests with a static subject and with a tripod as you or your subject may be rocking slightly back and forth.Please note you also have a global lens adjustment which cumulated with the individual lens adjustment could allow you to adjust the equivalent of -20;0 or 0;+20. Although that will probably induce issues with your other glass.

Could you explain how I "access" this global lens adjustment? Does this mean it would stay adjusted on any lens?

Sorry I didn't realise you had a Kx, I don't think it has the global adjustment that can be found on K5

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miles green
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Re: Sigma 50mm 1.4 soft?
In reply to Aidan Gibson, Apr 22, 2013

Aidan Gibson wrote:

I take it from your comment on +-10 your not really sure what or how to calibrate your camera.?

On my K-x I never used auto focus lenses, I got them with my IIs 4 weeks ago so no, I have no idea about calibration of the lenses/camera.

Hi Aidan,

First you have to exclude focus error. That's the hard part, especially when not in a testing environment. Figure out AF microadjustments. Also, I have a 3rd party focusing screen on my K5 (the ee-S) that way i know where i'm focusing. Be patient with fast lens, it's far from easy.

The Sigma 50 is supposedly a very nice lens, sharp wide open and vith very nice bokeh, thanks to its large front element. (I say supposedly as i've never used one).

Show us a few shots, we'll be able to help more.

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Cosmo Not
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Re: Sigma 50mm 1.4 soft?
In reply to James O'Neill, Apr 23, 2013

Agreed. I had several lenses with my Rebel and just bought the DA35mm for my K-5. None of them are as sharp wide open, although some are better than others. I believe the softness on many is actually spherical aberation, the hazy look that blurs edges when wide open. Combine this with slightly missed focusing and it will look very soft. DOF at F/1.4 is pretty thin.

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