Sigma 50mm 1.4 soft?

Started Apr 21, 2013 | Discussions
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Aidan Gibson Regular Member • Posts: 109
Sigma 50mm 1.4 soft?

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-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 Pentax smc DA 18-55mm F3.5-5.6 AL WR +1 more
Pentax K-5
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Winder Senior Member • Posts: 1,453
Re: Sigma 50mm 1.4 soft?

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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Contax 645, Canon 5D (sold), Olympus E-3 (sold), Playing with a K-7 and K-5

 Winder's gear list:Winder's gear list
Pentax K-3 Sony Alpha 7 II Pentax K-1 Sigma 50mm F1.4 EX DG HSM Pentax smc FA 31mm F1.8 AL Limited +4 more
Infrabasse Regular Member • Posts: 342
Re: Sigma 50mm 1.4 soft?

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?

 Infrabasse's gear list:Infrabasse's gear list
Canon PowerShot S95 Pentax K-5 Pentax Q Pentax K-30 Sigma 10-20mm F4-5.6 EX DC HSM +10 more
MightyMike Forum Pro • Posts: 34,533
Re: Sigma 50mm 1.4 soft?

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

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Mike from Canada
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awaldram
awaldram Forum Pro • Posts: 12,316
Re: Sigma 50mm 1.4 soft?

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.

 awaldram's gear list:awaldram's gear list
Pentax K-x Pentax Q Pentax Q7 Pentax K-3 Pentax smc DA* 55mm F1.4 SDM +15 more
Aidan Gibson OP Regular Member • Posts: 109
Re: Sigma 50mm 1.4 soft?

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?

 Aidan Gibson's gear list:Aidan Gibson's gear list
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 Pentax smc DA 18-55mm F3.5-5.6 AL WR +1 more
Aidan Gibson OP Regular Member • Posts: 109
Re: Sigma 50mm 1.4 soft?

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!

 Aidan Gibson's gear list:Aidan Gibson's gear list
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 Pentax smc DA 18-55mm F3.5-5.6 AL WR +1 more
Aidan Gibson OP Regular Member • Posts: 109
Re: Sigma 50mm 1.4 soft?

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-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 Pentax smc DA 18-55mm F3.5-5.6 AL WR +1 more
Aidan Gibson OP Regular Member • Posts: 109
Re: Sigma 50mm 1.4 soft?

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.

 Aidan Gibson's gear list:Aidan Gibson's gear list
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 Pentax smc DA 18-55mm F3.5-5.6 AL WR +1 more
James O'Neill Veteran Member • Posts: 4,106
Re: Sigma 50mm 1.4 soft?

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.

Infrabasse Regular Member • Posts: 342
Re: Sigma 50mm 1.4 soft?

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

 Infrabasse's gear list:Infrabasse's gear list
Canon PowerShot S95 Pentax K-5 Pentax Q Pentax K-30 Sigma 10-20mm F4-5.6 EX DC HSM +10 more
miles green
miles green Veteran Member • Posts: 5,192
Re: Sigma 50mm 1.4 soft?

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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Miles Green
Pentaxian with chronic LBA
Corfu, Greece

 miles green's gear list:miles green's gear list
Pentax K-5 Pentax K-1 Sigma 70-200mm F2.8 EX DG Macro HSM II Pentax smc DA 21mm F3.2 AL Limited Pentax smc FA 31mm F1.8 AL Limited +10 more
Cosmo Not Junior Member • Posts: 28
Re: Sigma 50mm 1.4 soft?

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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