Pentax 645Z lens aperture control

TrevorA · 03-30-2020, 06:33 AM

Hello
I am planning to buy a Pentax 645Z and various lenses, including the 25mm f/4. I would also like to use the Pentax 645 lenses on a Sony A7Rii via the Fotodiox Pro TLT ROKR - Tilt / Shift Lens Mount Adapter for Pentax 645 (P645) Mount SLR Lenses to Sony Alpha E-Mount Mirrorless Camera Body.

I can't see an aperture ring on the lens, so is there any way that I can change the lens aperture when using this or other 645Z lenses on the A7Rii?

Thank you for your assistance!

Trevor

chrism888 · 03-30-2020, 07:46 AM

Looking at images of the lens, I would agree with you, certainly the older 645 lenses have an aperture control ring, my 28 - 45 doesn't either, but all the other lenses I have do including the 80mm - 160 / 45mm - 85mm. You could opt for the 35mm instead, this has an aperture ring.

texandrews · 03-30-2020, 09:09 AM

Yes, some of the newer lenses don't have aperture rings anymore. Pity....

**pentaxus** · 03-30-2020, 10:22 PM

Some of the new lenses have an electric diaphragm to eliminate aperture control issues. That solution eliminates the possibility of aperture rings

TrevorA · 03-31-2020, 12:00 AM

Originally posted by chrism888

Looking at images of the lens, I would agree with you, certainly the older 645 lenses have an aperture control ring, my 28 - 45 doesn't either, but all the other lenses I have do including the 80mm - 160 / 45mm - 85mm. You could opt for the 35mm instead, this has an aperture ring.

Thank you. Is there an older version of the 25mm f/4 lens for Pentax 645 that does have a physical aperture ring?

Sandy Hancock · 03-31-2020, 12:12 AM

Originally posted by TrevorA

Is there an older version of the 25mm f/4 lens for Pentax 645 that does have a physical aperture ring?

Neither the DFA or the DA version of the 25/4.0 have an aperture ring.

Your next best option is the DFA645 35/3.5, which is a really nice wide angle lens too. Just not ultra wide....

There is of course a multitude of 24mm lenses you can adapt to your full frame Sony - many of which will be faster, smaller, cheaper and probably better for that format.

TrevorA · 03-31-2020, 11:48 PM

Sandy
Thank you for this information and advice.
Trevor

03-30-2020, 06:33 AM	#1
TrevorA New Member Join Date: Mar 2020 Posts: 12	Pentax 645Z lens aperture control Hello I am planning to buy a Pentax 645Z and various lenses, including the 25mm f/4. I would also like to use the Pentax 645 lenses on a Sony A7Rii via the Fotodiox Pro TLT ROKR - Tilt / Shift Lens Mount Adapter for Pentax 645 (P645) Mount SLR Lenses to Sony Alpha E-Mount Mirrorless Camera Body. I can't see an aperture ring on the lens, so is there any way that I can change the lens aperture when using this or other 645Z lenses on the A7Rii? Thank you for your assistance! Trevor

03-31-2020, 12:12 AM	#6
Sandy Hancock Moderator Site Supporter Join Date: Feb 2012 Location: Adelaide Hills, South Australia Photos: Gallery \| Albums Posts: 9,409	Originally posted by TrevorA Is there an older version of the 25mm f/4 lens for Pentax 645 that does have a physical aperture ring? Neither the DFA or the DA version of the 25/4.0 have an aperture ring. Your next best option is the DFA645 35/3.5, which is a really nice wide angle lens too. Just not ultra wide.... There is of course a multitude of 24mm lenses you can adapt to your full frame Sony - many of which will be faster, smaller, cheaper and probably better for that format. Last edited by Sandy Hancock; 03-31-2020 at 12:18 AM.

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03-30-2020, 07:46 AM	#2
chrism888 Senior Member Join Date: Feb 2012 Posts: 131	Looking at images of the lens, I would agree with you, certainly the older 645 lenses have an aperture control ring, my 28 - 45 doesn't either, but all the other lenses I have do including the 80mm - 160 / 45mm - 85mm. You could opt for the 35mm instead, this has an aperture ring.

03-30-2020, 09:09 AM	#3
texandrews Moderator Join Date: Apr 2014 Location: Baltimore Photos: Albums Posts: 1,817	Yes, some of the newer lenses don't have aperture rings anymore. Pity....

03-30-2020, 10:22 PM	#4
pentaxus Site Supporter Join Date: Jun 2010 Location: Central Coast, CA Posts: 886	Some of the new lenses have an electric diaphragm to eliminate aperture control issues. That solution eliminates the possibility of aperture rings

03-31-2020, 12:00 AM	#5
TrevorA New Member Join Date: Mar 2020 Posts: 12 Original Poster	Originally posted by chrism888 Looking at images of the lens, I would agree with you, certainly the older 645 lenses have an aperture control ring, my 28 - 45 doesn't either, but all the other lenses I have do including the 80mm - 160 / 45mm - 85mm. You could opt for the 35mm instead, this has an aperture ring. Thank you. Is there an older version of the 25mm f/4 lens for Pentax 645 that does have a physical aperture ring?

03-31-2020, 11:48 PM	#7
TrevorA New Member Join Date: Mar 2020 Posts: 12 Original Poster	Sandy Thank you for this information and advice. Trevor

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