Re: How to adapt Sigma 8-16mm for Pentax K1

[Larry Colen]

Jos de Fotograaf wrote:

Good idea, Larry, I will take some before / after pictures for reference

I changed my plan a bit, The lens has a protection tube that shifts over
sun-head when the lens is in the camera bag.

I will copy the sunhead on this tube, this becomes now a detachable
sunhead for APS-C use.

The original fixed head I will cut away comepletely


Please take pictures of your work in progress, I'm interested to see how 
it works out. Who knows, maybe I'll eventually track down an 8-16 and do 
the same.





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Re: How to adapt Sigma 8-16mm for Pentax K1

[Jos de Fotograaf]

Good idea, Larry, I will take some before / after pictures for reference

I changed my plan a bit, The lens has a protection tube that shifts over 
sun-head when the lens is in the camera bag.


I will copy  the sunhead on this tube, this becomes now a detachable 
sunhead for APS-C use.


The original fixed head I will cut away comepletely

On 28-Feb-17 22:36, Larry Colen wrote:
Could you maybe post some pictures showing the vignetting? Maybe of a 
grid so that you can quantify the difference you make comparing with 
in progress photos?


Do you maybe want to try trimming one corner of the petal hood so you 
can compare with the original and see if it is making a difference in 
that one corner?  Perhaps the lower left because that one is likely to 
be down no matter whether you are holding the camera and landscape or 
portrait mode?




Jos de Fotograaf wrote:

You're right: the hood is permanently attached. Your suggestion to
remove it completely will be my back-up solution if my cutting fails.

The front lens is extremely ball shaped, that makes it vulnerable in
practical use.

My step one will be to cut away from the hood just keeping enough to
avoid the lens toughing the table if I put the lens on the table with
front lens down.

If in that stage I can reach FF coverage down to 12 mm, I am satisfied
for the time being.




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Re: How to adapt Sigma 8-16mm for Pentax K1

[Larry Colen]

Jos de Fotograaf wrote:

You're right: the hood is permanently attached. Your suggestion to
remove it completely will be my back-up solution if my cutting fails.

The front lens is extremely ball shaped, that makes it vulnerable in
practical use.

My step one will be to cut away from the hood just keeping enough to
avoid the lens toughing the table if I put the lens on the table with
front lens down.

If in that stage I can reach FF coverage down to 12 mm, I am satisfied
for the time being.


Could you maybe post some pictures showing the vignetting? Maybe of a 
grid so that you can quantify the difference you make comparing with in 
progress photos?


Do you maybe want to try trimming one corner of the petal hood so you 
can compare with the original and see if it is making a difference in 
that one corner?  Perhaps the lower left because that one is likely to 
be down no matter whether you are holding the camera and landscape or 
portrait mode?


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Re: How to adapt Sigma 8-16mm for Pentax K1

[Jos de Fotograaf]

The lens has a very nice image on APSC.

Optically the lens is rotation symmetrical.

So cutting the top and bottom pedal will for sure give me a perfect 1:1 
8mm image, without any corner vignetting!!!


Cutting the side pedals will increase the FF image, at lesser optical 
performance, how much lesser has to be seen, also corner vignetting will 
become clear when zooming out...


On 26-Feb-17 20:14, Boris Liberman wrote:

I would suggest a different approach. Mount the lens on a full frame
camera, force it to FF mode, and actually take a picture. Then, given
that K-1 has extremely good sensor and that this is going to be an
experiment anyway, use editing software to lighten up the dark
corners. Then, I think it would become evident if this whole exercise
is worthwhile.

I would hazard a guess, that even if the lens is molested by removing
whatever seems to be on the way of full frame coverage and ultra-wide
angle, it would actually turn out that the image quality in these
corners is such that this whole thing is really not worth it.

Rather keep the excellent super-wide lens *designed* for APS-C sensor
and use it for whatever it was actually designed. Let's see - 8mm at
wide end, this gives an angle similar to that of 12mm lens on FF
camera. This is immensely wide.

On Sun, Feb 26, 2017 at 8:58 PM, Larry Colen  wrote:

It's permanently attached.  He could try talking some photos highlighting 
portions of the good with a laser pointer.


On February 26, 2017 10:04:21 AM PST, Bipin Gupta  wrote:

STOP! Do not cut the Lens Hood out first. Note, it has a flower petal
type hood with the longer petal on the top & bottom.
It's these longer ones that causes the vignetting.
Try twisting it to the LH / RH position from the top. Take shots and
see the results.

If it won't budge (after you have tried both the CCW & CW twist), mark
the top & bottom petals to follow the petal shape. Now use the smaller
1/4 inch hack saw blade without the handle.
Check the photo. Go on cutting by trial and error.
Make sure you don't graze the lens. Stick a 3M Post It on the Lens as
protection.
Then use emery paper to smoothen the rough cut surface.

If the LH / RH vertical petals are the culprit too, mark and cut with
the hack saw.

Good Luck.
Bipin

There is nothing worse than a sharp image of a fuzzy concept -  Ansel
Adams

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Re: How to adapt Sigma 8-16mm for Pentax K1

[Jos de Fotograaf]

Bipin, thks for your tips.

plse see my remarks in your text


On 26-Feb-17 19:04, Bipin Gupta wrote:

STOP! Do not cut the Lens Hood out first. Note, it has a flower petal
type hood with the longer petal on the top & bottom.--> correct
It's these longer ones that causes the vignetting.--> not correct 
shading starts at same moment when zooming out
Try twisting it to the LH / RH position from the top. Take shots and
see the results.> cannot twist

If it won't budge (after you have tried both the CCW & CW twist), mark
the top & bottom petals to follow the petal shape. Now use the smaller
1/4 inch hack saw blade without the handle.
Check the photo. Go on cutting by trial and error.
Make sure you don't graze the lens. Stick a 3M Post It on the Lens as
protection.---> good idea
Then use emery paper to smoothen the rough cut surface.

If the LH / RH vertical petals are the culprit too, mark and cut with
the hack saw.

Good Luck.-> thanks!
Bipin

There is nothing worse than a sharp image of a fuzzy concept -  Ansel Adams




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Re: How to adapt Sigma 8-16mm for Pentax K1

[Jos de Fotograaf]

You are right, but I am sure that the shading is dominantly caused by 
the hood.


It is not in the corners but away from the corners, clearly due to the 
pedal shaped hood.


The corners start vignetting at approx 13mm


On 26-Feb-17 16:22, Bruce Walker wrote:

Are you quite certain the vignetting isn't from a decreasing image
circle as you zoom out?

I don't know one way or the other, but if you cut the hood and
discover that doesn't fix the problem, you'll be mighty pissed. :)


On Sat, Feb 25, 2017 at 2:31 PM, Jos de Fotograaf
 wrote:

I have the Sigma 8-16mm and it gave me nice pictures on the K5. Sharper than
the Sigma 10-12 EX that I had for a while.

Using the 8-16mm on K1 in FF mode, is okay at 16mm, but zooming out, brings
in shadowing from the sun shade.

The sun shade is fixed to the lens and I am thinking of cutting away a part
of the shade.

Is this a good idea?

And what is the best way to cut, with a sharp knife or with a Dremel, to
maintain a nice look?

Any thoughts?

Greetz, Jos


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Re: How to adapt Sigma 8-16mm for Pentax K1

[Jos de Fotograaf]

You're right: the hood is permanently attached. Your suggestion to 
remove it completely will be my back-up solution if my cutting fails.


The front lens is extremely ball shaped, that makes it vulnerable in 
practical use.


My step one will be to cut away from the hood just keeping enough to 
avoid the lens toughing the table if I put the lens on the table with 
front lens down.


If in that stage I can reach FF coverage down to 12 mm, I am satisfied 
for the time being.


I will make a carton copy of the hood before starting to cut.


On 26-Feb-17 15:36, P. J. Alling wrote:
I think he said it was permanently attached to the lens.  I know I 
could go back and read his original post, but I'm basically lazy this 
morning, possibly every morning.  That makes a mistake very 
expensive.  Personally I'd just remove it entirely and figure out 
something from ground zero, unless I thought that removal would have 
important consequences.



On 2/26/2017 9:16 AM, Steve Cottrell wrote:

On 26/2/17, Jos de Fotograaf, discombobulated, unleashed:


Must be alternative knowledge?

Ha ha - an alternative reality maybe ;-)

If you're going to cut a lens shade up, before you do I would suggest
making some test hoods out of cardboard first, using the existing hood
as a template. That way you can optimise the shading for your needs.

If the hood you are going to cut is not expensive then I would try and
buy more of them as further test mules.

Some hoods are made of extremely hard plastic, others (like some Canon
hoods) are much softer and more flexible.

For a precision job a laser cutting device would give pretty clean
results. For best cheapest, sure a Dremel. Or you could use some fine
modelling saws. Either way you're going to end up with some rough edges
that will need sanding. Suggest nail files for this, rather than actual
sand paper.

Good luck!







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Re: How to adapt Sigma 8-16mm for Pentax K1

[Boris Liberman]

I would suggest a different approach. Mount the lens on a full frame
camera, force it to FF mode, and actually take a picture. Then, given
that K-1 has extremely good sensor and that this is going to be an
experiment anyway, use editing software to lighten up the dark
corners. Then, I think it would become evident if this whole exercise
is worthwhile.

I would hazard a guess, that even if the lens is molested by removing
whatever seems to be on the way of full frame coverage and ultra-wide
angle, it would actually turn out that the image quality in these
corners is such that this whole thing is really not worth it.

Rather keep the excellent super-wide lens *designed* for APS-C sensor
and use it for whatever it was actually designed. Let's see - 8mm at
wide end, this gives an angle similar to that of 12mm lens on FF
camera. This is immensely wide.

On Sun, Feb 26, 2017 at 8:58 PM, Larry Colen  wrote:
> It's permanently attached.  He could try talking some photos highlighting 
> portions of the good with a laser pointer.
>
>
> On February 26, 2017 10:04:21 AM PST, Bipin Gupta  wrote:
>>STOP! Do not cut the Lens Hood out first. Note, it has a flower petal
>>type hood with the longer petal on the top & bottom.
>>It's these longer ones that causes the vignetting.
>>Try twisting it to the LH / RH position from the top. Take shots and
>>see the results.
>>
>>If it won't budge (after you have tried both the CCW & CW twist), mark
>>the top & bottom petals to follow the petal shape. Now use the smaller
>>1/4 inch hack saw blade without the handle.
>>Check the photo. Go on cutting by trial and error.
>>Make sure you don't graze the lens. Stick a 3M Post It on the Lens as
>>protection.
>>Then use emery paper to smoothen the rough cut surface.
>>
>>If the LH / RH vertical petals are the culprit too, mark and cut with
>>the hack saw.
>>
>>Good Luck.
>>Bipin
>>
>>There is nothing worse than a sharp image of a fuzzy concept -  Ansel
>>Adams
>
> --
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> http://red4est.com/lrc
>
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Re: How to adapt Sigma 8-16mm for Pentax K1

[Larry Colen]

It's permanently attached.  He could try talking some photos highlighting 
portions of the good with a laser pointer.


On February 26, 2017 10:04:21 AM PST, Bipin Gupta  wrote:
>STOP! Do not cut the Lens Hood out first. Note, it has a flower petal
>type hood with the longer petal on the top & bottom.
>It's these longer ones that causes the vignetting.
>Try twisting it to the LH / RH position from the top. Take shots and
>see the results.
>
>If it won't budge (after you have tried both the CCW & CW twist), mark
>the top & bottom petals to follow the petal shape. Now use the smaller
>1/4 inch hack saw blade without the handle.
>Check the photo. Go on cutting by trial and error.
>Make sure you don't graze the lens. Stick a 3M Post It on the Lens as
>protection.
>Then use emery paper to smoothen the rough cut surface.
>
>If the LH / RH vertical petals are the culprit too, mark and cut with
>the hack saw.
>
>Good Luck.
>Bipin
>
>There is nothing worse than a sharp image of a fuzzy concept -  Ansel
>Adams

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Re: How to adapt Sigma 8-16mm for Pentax K1

[Bruce Walker]

Are you quite certain the vignetting isn't from a decreasing image
circle as you zoom out?

I don't know one way or the other, but if you cut the hood and
discover that doesn't fix the problem, you'll be mighty pissed. :)


On Sat, Feb 25, 2017 at 2:31 PM, Jos de Fotograaf
 wrote:
> I have the Sigma 8-16mm and it gave me nice pictures on the K5. Sharper than
> the Sigma 10-12 EX that I had for a while.
>
> Using the 8-16mm on K1 in FF mode, is okay at 16mm, but zooming out, brings
> in shadowing from the sun shade.
>
> The sun shade is fixed to the lens and I am thinking of cutting away a part
> of the shade.
>
> Is this a good idea?
>
> And what is the best way to cut, with a sharp knife or with a Dremel, to
> maintain a nice look?
>
> Any thoughts?
>
> Greetz, Jos
>
>
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Re: How to adapt Sigma 8-16mm for Pentax K1

[P. J. Alling]

I think he said it was permanently attached to the lens.  I know I could 
go back and read his original post, but I'm basically lazy this morning, 
possibly every morning.  That makes a mistake very expensive.  
Personally I'd just remove it entirely and figure out something from 
ground zero, unless I thought that removal would have important 
consequences.



On 2/26/2017 9:16 AM, Steve Cottrell wrote:

On 26/2/17, Jos de Fotograaf, discombobulated, unleashed:


Must be alternative knowledge?

Ha ha - an alternative reality maybe ;-)

If you're going to cut a lens shade up, before you do I would suggest
making some test hoods out of cardboard first, using the existing hood
as a template. That way you can optimise the shading for your needs.

If the hood you are going to cut is not expensive then I would try and
buy more of them as further test mules.

Some hoods are made of extremely hard plastic, others (like some Canon
hoods) are much softer and more flexible.

For a precision job a laser cutting device would give pretty clean
results. For best cheapest, sure a Dremel. Or you could use some fine
modelling saws. Either way you're going to end up with some rough edges
that will need sanding. Suggest nail files for this, rather than actual
sand paper.

Good luck!




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Re: How to adapt Sigma 8-16mm for Pentax K1

[Steve Cottrell]

On 26/2/17, Jos de Fotograaf, discombobulated, unleashed:

>Must be alternative knowledge?

Ha ha - an alternative reality maybe ;-)

If you're going to cut a lens shade up, before you do I would suggest
making some test hoods out of cardboard first, using the existing hood
as a template. That way you can optimise the shading for your needs.

If the hood you are going to cut is not expensive then I would try and
buy more of them as further test mules.

Some hoods are made of extremely hard plastic, others (like some Canon
hoods) are much softer and more flexible.

For a precision job a laser cutting device would give pretty clean
results. For best cheapest, sure a Dremel. Or you could use some fine
modelling saws. Either way you're going to end up with some rough edges
that will need sanding. Suggest nail files for this, rather than actual
sand paper.

Good luck!

-- 


Cheers,
  Cotty


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||  (O)  |Web Video Production
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Re: How to adapt Sigma 8-16mm for Pentax K1

[Jos de Fotograaf]

Must be alternative knowledge?


On 26-Feb-17 01:19, Steve Cottrell wrote:

On 25/2/17, Jos de Fotograaf, discombobulated, unleashed:


And what is the best way to cut, with a sharp knife or with a Dremel, to
maintain a nice look?

The best way to cut is with your eyes closed and your hands at the mercy
of Beelzebub.

I know, trust me.




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Re: How to adapt Sigma 8-16mm for Pentax K1

[Steve Cottrell]

On 25/2/17, Jos de Fotograaf, discombobulated, unleashed:

>And what is the best way to cut, with a sharp knife or with a Dremel, to 
>maintain a nice look?

The best way to cut is with your eyes closed and your hands at the mercy
of Beelzebub.

I know, trust me.

-- 


Cheers,
  Cotty


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||  (O)  |Web Video Production
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