25mm vs 28-45mm comparison on 645Z

BostonUKshooter · 06-10-2017, 02:20 AM

Here's a link to a comparison between the 2 wide 645 lenses....not truly 'scientific' , but a good indication of what to expect for the extra 5 degrees FOV that the 25mm provides....the zoom is said to be a bit sharper in the centre, but the 25m better at the edges..?.....now an 'extinct' lens as it was quietly withdrawn by Ricoh...
http://www.alexmunoz.net/field-view-comparison-28-45mm-f4-5-25mm-f4-0/

Adam · 06-10-2017, 03:10 AM

Originally posted by BostonUKshooter

now an 'extinct' lens as it was quietly withdrawn by Ricoh...

What happened is they were still losing money on it due to optical QC issues, and it was no longer economical to produce. The reps I spoke with about that, several years ago, said the lens might eventually make a comeback once the reliability could be improved.

mikeSF · 06-10-2017, 08:12 AM - **1 Like**

thanks Alex Munoz for the blog post and thanks BostonShooter for sharing it.

I finally tried the 645Z with DFA25/4 and DFA35/3.5 for wide field astro-photography, and see enormous potential if only there were a wider and faster lens available. I think a 20mm f/2.4 prime would be the magic formula for some great night sky shots.
Did someone say full frame 645 sensor? well, that too, lol.

Phone Home
645Z & DFA25

Alone
645Z & DFA35

**Digitalis** · 06-10-2017, 06:22 PM - **1 Like**

Nice work there Mike.

Originally posted by mikeSF

I think a 20mm f/2.4 prime would be the magic formula for some great night sky shots.

A lens like that for 645 format even if it was designed for 44X33mm sensors would still be huge.

itshimitis · 06-10-2017, 06:36 PM - **1 Like**

I think a f/4 ultra wide is more likely and easier to carry

itshimitis · 06-10-2017, 06:36 PM

I think a f/4 ultra wide is more likely and easier to carry

mikeSF · 06-11-2017, 09:37 AM

Originally posted by Digitalis

Nice work there Mike.

A lens like that for 645 format even if it was designed for 44X33mm sensors would still be huge.

I agree. And no doubt expensive too.

BostonUKshooter · 06-11-2017, 11:18 PM

Originally posted by mikeSF

thanks Alex Munoz for the blog post and thanks BostonShooter for sharing it.

I finally tried the 645Z with DFA25/4 and DFA35/3.5 for wide field astro-photography, and see enormous potential if only there were a wider and faster lens available. I think a 20mm f/2.4 prime would be the magic formula for some great night sky shots.
Did someone say full frame 645 sensor? well, that too, lol.

Phone Home
645Z & DFA25

Alone
645Z & DFA35

Hi Mike - whats the EXIF for the first shot? Thks, Ian

Ryan Tischer · 06-12-2017, 09:54 AM

I own both the D FA 25mm and 28-45mm. The 28-45mm is a bit sharper at all apertures (by far the sharpest lens I've ever used), though the 25mm is quite sharp from f/10-f/14 (I don't often shoot with it at wider apertures). It starts to fall off just a touch at f/16 and more by f/22. The 25mm is a great lens to have...that 3mm makes a big difference in the wide angle. I'd love it if Pentax came out with something even a bit wider.

Sarnian · 06-12-2017, 02:24 PM

Have you tried your D-FA 25mm on a Pentax 645N? I tried it on my 645Nii and, boy, it's W---I---D---E!! Something like 14mm in 135 terms!

mikeSF · 06-12-2017, 02:48 PM

Originally posted by BostonUKshooter

Hi Mike - whats the EXIF for the first shot? Thks, Ian

Ian, It was 25sec at f/5, ISO8000
There's a little star streaking upon close inspection, but ISO 8,000 seemed to be the highest I could take it before noise gets out of control.

---------- Post added 06-12-2017 at 02:50 PM ----------

Originally posted by Sarnian

Have you tried your D-FA 25mm on a Pentax 645N? I tried it on my 645Nii and, boy, it's W---I---D---E!! Something like 14mm in 135 terms!

this could be why we havent seen a wider lens in the roadmap...645 full frame sensor would cover that.

**Ed Hurst** · 06-12-2017, 05:39 PM - **1 Like**

Lovely shots, Mike - the first one, especially. One frame, or two with blending (to tame the bright red light)?

mikeSF · 06-12-2017, 07:09 PM

Originally posted by Ed Hurst

Lovely shots, Mike - the first one, especially. One frame, or two with blending (to tame the bright red light)?

The light was not too bright to require bracketing; I just brought down the red luminance in ACR.

**Ed Hurst** · 06-12-2017, 08:23 PM - **1 Like**

It's splendid!

---------- Post added 06-13-17 at 01:25 PM ----------

Originally posted by mikeSF

thanks Alex Munoz for the blog post and thanks BostonShooter for sharing it.

I finally tried the 645Z with DFA25/4 and DFA35/3.5 for wide field astro-photography, and see enormous potential if only there were a wider and faster lens available. I think a 20mm f/2.4 prime would be the magic formula for some great night sky shots.
Did someone say full frame 645 sensor? well, that too, lol.

Phone Home
645Z & DFA25

Alone
645Z & DFA35

Could not agree more. The system, if it's to be the astro king, needs a fast 20mm or 21mm... It may be impractical, expensive, etc. and it may be something already done well by FF systems. But I want it very much!

BostonUKshooter · 06-12-2017, 11:15 PM - **1 Like**

Originally posted by mikeSF

Ian, It was 25sec at f/5, ISO8000
There's a little star streaking upon close inspection, but ISO 8,000 seemed to be the highest I could take it before noise gets out of control.

---------- Post added 06-12-2017 at 02:50 PM ----------

this could be why we havent seen a wider lens in the roadmap...645 full frame sensor would cover that.

Thanks ....cool image....

06-10-2017, 02:20 AM	#1
BostonUKshooter Veteran Member Join Date: Nov 2014 Posts: 338	25mm vs 28-45mm comparison on 645Z Here's a link to a comparison between the 2 wide 645 lenses....not truly 'scientific' , but a good indication of what to expect for the extra 5 degrees FOV that the 25mm provides....the zoom is said to be a bit sharper in the centre, but the 25m better at the edges..?.....now an 'extinct' lens as it was quietly withdrawn by Ricoh... http://www.alexmunoz.net/field-view-comparison-28-45mm-f4-5-25mm-f4-0/

06-10-2017, 03:10 AM	#2
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,594	Originally posted by BostonUKshooter now an 'extinct' lens as it was quietly withdrawn by Ricoh... What happened is they were still losing money on it due to optical QC issues, and it was no longer economical to produce. The reps I spoke with about that, several years ago, said the lens might eventually make a comeback once the reliability could be improved. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

06-12-2017, 02:48 PM	#11
mikeSF Pentaxian Join Date: Jan 2009 Location: East Bay Area, CA Photos: Gallery Posts: 6,620	Originally posted by BostonUKshooter Hi Mike - whats the EXIF for the first shot? Thks, Ian Ian, It was 25sec at f/5, ISO8000 There's a little star streaking upon close inspection, but ISO 8,000 seemed to be the highest I could take it before noise gets out of control. ---------- Post added 06-12-2017 at 02:50 PM ---------- Originally posted by Sarnian Have you tried your D-FA 25mm on a Pentax 645N? I tried it on my 645Nii and, boy, it's W---I---D---E!! Something like 14mm in 135 terms! this could be why we havent seen a wider lens in the roadmap...645 full frame sensor would cover that. Last edited by mikeSF; 06-12-2017 at 07:06 PM.

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06-10-2017, 08:12 AM - 1 Like	#3
mikeSF Pentaxian Join Date: Jan 2009 Location: East Bay Area, CA Photos: Gallery Posts: 6,620	thanks Alex Munoz for the blog post and thanks BostonShooter for sharing it. I finally tried the 645Z with DFA25/4 and DFA35/3.5 for wide field astro-photography, and see enormous potential if only there were a wider and faster lens available. I think a 20mm f/2.4 prime would be the magic formula for some great night sky shots. Did someone say full frame 645 sensor? well, that too, lol. Phone Home 645Z & DFA25 Alone 645Z & DFA35

06-10-2017, 06:22 PM - 1 Like	#4
Digitalis Site Supporter Join Date: Mar 2009 Location: Melbourne, Victoria Photos: Gallery Posts: 11,694	Nice work there Mike. Originally posted by mikeSF I think a 20mm f/2.4 prime would be the magic formula for some great night sky shots. A lens like that for 645 format even if it was designed for 44X33mm sensors would still be huge.

06-10-2017, 06:36 PM - 1 Like	#5
itshimitis Pentaxian Join Date: May 2011 Location: All over the place Posts: 3,535	I think a f/4 ultra wide is more likely and easier to carry

06-10-2017, 06:36 PM	#6
itshimitis Pentaxian Join Date: May 2011 Location: All over the place Posts: 3,535	I think a f/4 ultra wide is more likely and easier to carry

06-11-2017, 09:37 AM	#7
mikeSF Pentaxian Join Date: Jan 2009 Location: East Bay Area, CA Photos: Gallery Posts: 6,620	Originally posted by Digitalis Nice work there Mike. A lens like that for 645 format even if it was designed for 44X33mm sensors would still be huge. I agree. And no doubt expensive too.

06-11-2017, 11:18 PM	#8
BostonUKshooter Veteran Member Join Date: Nov 2014 Posts: 338 Original Poster	Originally posted by mikeSF thanks Alex Munoz for the blog post and thanks BostonShooter for sharing it. I finally tried the 645Z with DFA25/4 and DFA35/3.5 for wide field astro-photography, and see enormous potential if only there were a wider and faster lens available. I think a 20mm f/2.4 prime would be the magic formula for some great night sky shots. Did someone say full frame 645 sensor? well, that too, lol. Phone Home 645Z & DFA25 Alone 645Z & DFA35 Hi Mike - whats the EXIF for the first shot? Thks, Ian

06-12-2017, 09:54 AM	#9
Ryan Tischer Veteran Member Join Date: Feb 2012 Location: Duluth, Minnesota Photos: Albums Posts: 458	I own both the D FA 25mm and 28-45mm. The 28-45mm is a bit sharper at all apertures (by far the sharpest lens I've ever used), though the 25mm is quite sharp from f/10-f/14 (I don't often shoot with it at wider apertures). It starts to fall off just a touch at f/16 and more by f/22. The 25mm is a great lens to have...that 3mm makes a big difference in the wide angle. I'd love it if Pentax came out with something even a bit wider.

06-12-2017, 02:24 PM	#10
Sarnian Senior Member Join Date: Oct 2015 Posts: 101	Have you tried your D-FA 25mm on a Pentax 645N? I tried it on my 645Nii and, boy, it's W---I---D---E!! Something like 14mm in 135 terms!

06-12-2017, 05:39 PM - 1 Like	#12
Ed Hurst Site Supporter Join Date: May 2010 Location: Sydney Posts: 1,657	Lovely shots, Mike - the first one, especially. One frame, or two with blending (to tame the bright red light)?

06-12-2017, 07:09 PM	#13
mikeSF Pentaxian Join Date: Jan 2009 Location: East Bay Area, CA Photos: Gallery Posts: 6,620	Originally posted by Ed Hurst Lovely shots, Mike - the first one, especially. One frame, or two with blending (to tame the bright red light)? The light was not too bright to require bracketing; I just brought down the red luminance in ACR.

06-12-2017, 08:23 PM - 1 Like	#14
Ed Hurst Site Supporter Join Date: May 2010 Location: Sydney Posts: 1,657	It's splendid! ---------- Post added 06-13-17 at 01:25 PM ---------- Originally posted by mikeSF thanks Alex Munoz for the blog post and thanks BostonShooter for sharing it. I finally tried the 645Z with DFA25/4 and DFA35/3.5 for wide field astro-photography, and see enormous potential if only there were a wider and faster lens available. I think a 20mm f/2.4 prime would be the magic formula for some great night sky shots. Did someone say full frame 645 sensor? well, that too, lol. Phone Home 645Z & DFA25 Alone 645Z & DFA35 Could not agree more. The system, if it's to be the astro king, needs a fast 20mm or 21mm... It may be impractical, expensive, etc. and it may be something already done well by FF systems. But I want it very much!

06-12-2017, 11:15 PM - 1 Like	#15
BostonUKshooter Veteran Member Join Date: Nov 2014 Posts: 338 Original Poster	Originally posted by mikeSF Ian, It was 25sec at f/5, ISO8000 There's a little star streaking upon close inspection, but ISO 8,000 seemed to be the highest I could take it before noise gets out of control. ---------- Post added 06-12-2017 at 02:50 PM ---------- this could be why we havent seen a wider lens in the roadmap...645 full frame sensor would cover that. Thanks ....cool image....