Post your medium format photos!

**kaseki** · 02-08-2021, 09:22 AM - **1 Like**

Originally posted by TDvN57

...
Comments and pixel peeping appreciated....

With a 1000-mm focal length, each micron of focal plane detector observes a microradian of far field. Atmospheric turbulence over kilometers, aperture-averaged by the lens, is likely to be in the 10 microradian, rms, ballpark, comparable with the pixel field of view of the sensor. Hence, I would suggest that a 1.4x teleconverter on a 600mm lens is perhaps beyond the limit of resolution that can be had at long range for a 645Z (~5 micron pixels).

Very short exposure times of the order of a millisecond, if light allows, may freeze the atmosphere into isoplanatic patches of similar distortion, some of which some of the time will actually be relatively undisturbed, or even magnified, relative to the rest. So with enough attempts, an image of one of the mountaintop hikers might become fairly good, to the limit of the pixel resolution, at least.

**TDvN57** · 02-08-2021, 05:48 PM - **2 Likes**

Originally posted by kaseki

With a 1000-mm focal length, each micron of focal plane detector observes a microradian of far field. Atmospheric turbulence over kilometers, aperture-averaged by the lens, is likely to be in the 10 microradian, rms, ballpark, comparable with the pixel field of view of the sensor. Hence, I would suggest that a 1.4x teleconverter on a 600mm lens is perhaps beyond the limit of resolution that can be had at long range for a 645Z (~5 micron pixels).

Very short exposure times of the order of a millisecond, if light allows, may freeze the atmosphere into isoplanatic patches of similar distortion, some of which some of the time will actually be relatively undisturbed, or even magnified, relative to the rest. So with enough attempts, an image of one of the mountaintop hikers might become fairly good, to the limit of the pixel resolution, at least.

Thanks Kaseki, that does explain a lot.

I did a similar exercise last Saturday with the P67 400mm lens with the 67 TC 1.4.

The first picture is with the P67 400mm at f4, about a 140% crop. The outlines are much sharper and the foliage is much clearer than with the P645 600mm lens. The conditions were much different though, which may play a role. These were taken on a sunny day mid-afternoon with somewhat more atmospheric disturbance, so much that I could see the heatwaves on live-view. So I took a lot more pictures and selected the most clear ones. It could also be that the sunlight helped in resolving the foliage much clearer, not sure about that.

Same scene, but with the P67 Teleconverter 1.4. It seems as if the foliage is much clearer.

It looks to me as if the P67 400mm plus 1.4TC makes for an excellent combo. Comments?

mikeSF · 02-08-2021, 05:48 PM - **7 Likes**

I made it over to the Byron Hot Springs Hotel this morning...

Byron Hot Springs Hotel
pano w 645Z & A120, 2 exposure manual blend

**bobbotron** · 02-08-2021, 07:49 PM - **6 Likes**

My dog Winston, shot on a Pentax 645, with the 75mm lens. Printed on some excellent Foma RC paper. (I really like this paper, the velvet finish is great!)

Last edited by bobbotron; 02-09-2021 at 07:13 AM. Reason: Edited for typos

**RICHARD L.** · 02-09-2021, 05:50 AM

Originally posted by bobbotron

Pentax 656, I think with the 70mm

Typos, maybe ? 656 = 645 ? 70 mm lens = 75 mm f/2.8 lens ?

Regards

**bobbotron** · 02-09-2021, 05:57 AM

Originally posted by RICHARD L.

Typos, maybe ? 656 = 645 ? 70 mm lens = 75 mm f/2.8 lens ?

Regards

Oh yeah, yep that looks better.

**kaseki** · 02-09-2021, 10:53 AM

Originally posted by TDvN57

Thanks Kaseki, that does explain a lot.

I did a similar exercise last Saturday with the P67 400mm lens with the 67 TC 1.4.

The first picture is with the P67 400mm at f4, about a 140% crop. The outlines are much sharper and the foliage is much clearer than with the P645 600mm lens. The conditions were much different though, which may play a role. These were taken on a sunny day mid-afternoon with somewhat more atmospheric disturbance, so much that I could see the heatwaves on live-view. So I took a lot more pictures and selected the most clear ones. It could also be that the sunlight helped in resolving the foliage much clearer, not sure about that.

Same scene, but with the P67 Teleconverter 1.4. It seems as if the foliage is much clearer.

It looks to me as if the P67 400mm plus 1.4TC makes for an excellent combo. Comments?

I think, before looking at the comments that followed you, that the w/o TC looked sharper, but I wouldn't bet on any result that included the atmosphere. On the other hand, with the greater magnification of the w/ TC, the bushes separate better and the scene is more interesting.

w2ck · 02-09-2021, 03:37 PM

Hi,

Oops! The new 150 MP Pentax MF camera model number has leaked out! 656!

Or, not!

Stan

mikeSF · 02-09-2021, 06:00 PM - **5 Likes**

Silhouette
DFA25 645Z

**TDvN57** · 02-09-2021, 06:27 PM - **1 Like**

Originally posted by kaseki

I think, before looking at the comments that followed you, that the w/o TC looked sharper, but I wouldn't bet on any result that included the atmosphere. On the other hand, with the greater magnification of the w/ TC, the bushes separate better and the scene is more interesting.

I agree, what surprised me is how much clearer the 400mm lens is (with or without the TC) compared with the 600mm lens.

Granted it is not a very scientific comparison, but it does reflect a real life scenario for the type of shooting I do.

---------- Post added 2021-02-10 at 09:30 AM ----------

Originally posted by mikeSF

Silhouette
DFA25 645Z

Mike, that silhouette scene begs for a sundowner. Nice shot.

mikeSF · 02-09-2021, 07:11 PM - **8 Likes**

Fixer Upper
DFA 25 645Z

tuco · 02-10-2021, 01:08 PM - **8 Likes**

Playing around with focal plane orientation with old-school close up photography.

Ilford FP4+, D-23

**acoufap** · 02-10-2021, 01:22 PM

Originally posted by tuco

Playing around with focal plane orientation with old-school close up photography.

Ilford FP4+, D-23

Wonderful grey tone pictures!

mikeSF · 02-10-2021, 03:34 PM

Love these so much, tuco!

Originally posted by tuco

Playing around with focal plane orientation with old-school close up photography.

Ilford FP4+, D-23

tuco · 02-10-2021, 04:24 PM - **1 Like**

Originally posted by acoufap

Wonderful grey tone pictures!

Originally posted by mikeSF

Love these so much, tuco!

Thanks. They're fun to do this rainy time of year here.

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02-08-2021, 09:22 AM - 1 Like	#15916
kaseki Loyal Site Supporter Join Date: Dec 2017 Photos: Gallery \| Albums Posts: 1,138	Originally posted by TDvN57 ... Comments and pixel peeping appreciated.... With a 1000-mm focal length, each micron of focal plane detector observes a microradian of far field. Atmospheric turbulence over kilometers, aperture-averaged by the lens, is likely to be in the 10 microradian, rms, ballpark, comparable with the pixel field of view of the sensor. Hence, I would suggest that a 1.4x teleconverter on a 600mm lens is perhaps beyond the limit of resolution that can be had at long range for a 645Z (~5 micron pixels). Very short exposure times of the order of a millisecond, if light allows, may freeze the atmosphere into isoplanatic patches of similar distortion, some of which some of the time will actually be relatively undisturbed, or even magnified, relative to the rest. So with enough attempts, an image of one of the mountaintop hikers might become fairly good, to the limit of the pixel resolution, at least.

02-08-2021, 05:48 PM - 2 Likes	#15917
TDvN57 Loyal Site Supporter Join Date: Jul 2011 Location: Berlin Photos: Gallery Posts: 1,149	Originally posted by kaseki With a 1000-mm focal length, each micron of focal plane detector observes a microradian of far field. Atmospheric turbulence over kilometers, aperture-averaged by the lens, is likely to be in the 10 microradian, rms, ballpark, comparable with the pixel field of view of the sensor. Hence, I would suggest that a 1.4x teleconverter on a 600mm lens is perhaps beyond the limit of resolution that can be had at long range for a 645Z (~5 micron pixels). Very short exposure times of the order of a millisecond, if light allows, may freeze the atmosphere into isoplanatic patches of similar distortion, some of which some of the time will actually be relatively undisturbed, or even magnified, relative to the rest. So with enough attempts, an image of one of the mountaintop hikers might become fairly good, to the limit of the pixel resolution, at least. Thanks Kaseki, that does explain a lot. I did a similar exercise last Saturday with the P67 400mm lens with the 67 TC 1.4. The first picture is with the P67 400mm at f4, about a 140% crop. The outlines are much sharper and the foliage is much clearer than with the P645 600mm lens. The conditions were much different though, which may play a role. These were taken on a sunny day mid-afternoon with somewhat more atmospheric disturbance, so much that I could see the heatwaves on live-view. So I took a lot more pictures and selected the most clear ones. It could also be that the sunlight helped in resolving the foliage much clearer, not sure about that. Same scene, but with the P67 Teleconverter 1.4. It seems as if the foliage is much clearer. It looks to me as if the P67 400mm plus 1.4TC makes for an excellent combo. Comments?

02-08-2021, 05:48 PM - 7 Likes	#15918
mikeSF Pentaxian Join Date: Jan 2009 Location: East Bay Area, CA Photos: Gallery Posts: 6,620	I made it over to the Byron Hot Springs Hotel this morning... Byron Hot Springs Hotel pano w 645Z & A120, 2 exposure manual blend

02-08-2021, 07:49 PM - 6 Likes	#15919
bobbotron Site Supporter Join Date: Jan 2015 Location: Ottawa, ON Photos: Gallery Posts: 3,349	My dog Winston, shot on a Pentax 645, with the 75mm lens. Printed on some excellent Foma RC paper. (I really like this paper, the velvet finish is great!) Last edited by bobbotron; 02-09-2021 at 07:13 AM. Reason: Edited for typos

02-09-2021, 05:50 AM	#15920
RICHARD L. Loyal Site Supporter Join Date: Oct 2018 Location: Quebec City, Quebec Posts: 6,582	Originally posted by bobbotron Pentax 656, I think with the 70mm Typos, maybe ? 656 = 645 ? 70 mm lens = 75 mm f/2.8 lens ? Regards

02-09-2021, 05:57 AM	#15921
bobbotron Site Supporter Join Date: Jan 2015 Location: Ottawa, ON Photos: Gallery Posts: 3,349	Originally posted by RICHARD L. Typos, maybe ? 656 = 645 ? 70 mm lens = 75 mm f/2.8 lens ? Regards Oh yeah, yep that looks better.

02-09-2021, 10:53 AM	#15922
kaseki Loyal Site Supporter Join Date: Dec 2017 Photos: Gallery \| Albums Posts: 1,138	Originally posted by TDvN57 Thanks Kaseki, that does explain a lot. I did a similar exercise last Saturday with the P67 400mm lens with the 67 TC 1.4. The first picture is with the P67 400mm at f4, about a 140% crop. The outlines are much sharper and the foliage is much clearer than with the P645 600mm lens. The conditions were much different though, which may play a role. These were taken on a sunny day mid-afternoon with somewhat more atmospheric disturbance, so much that I could see the heatwaves on live-view. So I took a lot more pictures and selected the most clear ones. It could also be that the sunlight helped in resolving the foliage much clearer, not sure about that. Same scene, but with the P67 Teleconverter 1.4. It seems as if the foliage is much clearer. It looks to me as if the P67 400mm plus 1.4TC makes for an excellent combo. Comments? I think, before looking at the comments that followed you, that the w/o TC looked sharper, but I wouldn't bet on any result that included the atmosphere. On the other hand, with the greater magnification of the w/ TC, the bushes separate better and the scene is more interesting.

02-09-2021, 03:37 PM	#15923
w2ck Pentaxian Join Date: Apr 2020 Location: Raleigh, NC Photos: Albums Posts: 442	Hi, Oops! The new 150 MP Pentax MF camera model number has leaked out! 656! Or, not! Stan

02-09-2021, 06:00 PM - 5 Likes	#15924
mikeSF Pentaxian Join Date: Jan 2009 Location: East Bay Area, CA Photos: Gallery Posts: 6,620	Silhouette DFA25 645Z

02-09-2021, 06:27 PM - 1 Like	#15925
TDvN57 Loyal Site Supporter Join Date: Jul 2011 Location: Berlin Photos: Gallery Posts: 1,149	Originally posted by kaseki I think, before looking at the comments that followed you, that the w/o TC looked sharper, but I wouldn't bet on any result that included the atmosphere. On the other hand, with the greater magnification of the w/ TC, the bushes separate better and the scene is more interesting. I agree, what surprised me is how much clearer the 400mm lens is (with or without the TC) compared with the 600mm lens. Granted it is not a very scientific comparison, but it does reflect a real life scenario for the type of shooting I do. ---------- Post added 2021-02-10 at 09:30 AM ---------- Originally posted by mikeSF Silhouette DFA25 645Z Mike, that silhouette scene begs for a sundowner. Nice shot.

02-09-2021, 07:11 PM - 8 Likes	#15926
mikeSF Pentaxian Join Date: Jan 2009 Location: East Bay Area, CA Photos: Gallery Posts: 6,620	Fixer Upper DFA 25 645Z

02-10-2021, 01:08 PM - 8 Likes	#15927
tuco Pentaxian Join Date: Jul 2009 Location: Pugetopolis Posts: 11,026	Playing around with focal plane orientation with old-school close up photography. Ilford FP4+, D-23

02-10-2021, 01:22 PM	#15928
acoufap Site Supporter Join Date: Jan 2011 Location: Munich, Germany Photos: Gallery \| Albums Posts: 4,187	Originally posted by tuco Playing around with focal plane orientation with old-school close up photography. Ilford FP4+, D-23 Wonderful grey tone pictures!

02-10-2021, 03:34 PM	#15929
mikeSF Pentaxian Join Date: Jan 2009 Location: East Bay Area, CA Photos: Gallery Posts: 6,620	Love these so much, tuco! Originally posted by tuco Playing around with focal plane orientation with old-school close up photography. Ilford FP4+, D-23

02-10-2021, 04:24 PM - 1 Like	#15930
tuco Pentaxian Join Date: Jul 2009 Location: Pugetopolis Posts: 11,026	Originally posted by acoufap Wonderful grey tone pictures! Originally posted by mikeSF Love these so much, tuco! Thanks. They're fun to do this rainy time of year here.