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Mamiya Sekor 150mm F2.8
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PostPosted: Wed Jan 21, 2015 11:29 pm    Post subject: Mamiya Sekor 150mm F2.8 Reply with quote
Tested out the slightly longer 645 lens, first thing that became immediately apparent was how sharp this thing is wide open and how little CA is present too. Only longitudinal CA was evident. Sadly it doesn't focus closer than 1.5m (5ft), but it certainly equals both my tamron SP 180mm f2.5 and my nikkor 80-200mm f2.8 ED. Still got a few more m645 lenses to test yet, but I'm really liking the results so far.

IMG_6887 by --Kei--, on Flickr

IMG_6879 by --Kei--, on Flickr

IMG_6890 by --Kei--, on Flickr

IMG_6894 by --Kei--, on Flickr


PostPosted: Thu Jan 22, 2015 8:33 am    Post subject: Reply with quote
Yes, it is a nice lens, the 150/2.8 A.

I use it on a FF sensor EOS 5D3. With our without a short extension ring to get closer than 1,5m.

Effective focal length is about 90mm and effective min aperture value is 1,6 Smile

Stonington Seagull by Sigurd Ruschkowski, on Flickr

Fish Barrels by Sigurd Ruschkowski, on Flickr


Inverted Moustash Smiles by Sigurd Ruschkowski, on Flickr


Good Ones Smile by Sigurd Ruschkowski, on Flickr


House over looking the Bay by Sigurd Ruschkowski, on Flickr


PostPosted: Thu Jan 22, 2015 8:47 am    Post subject: Reply with quote
Sigurd Ruschkowski wrote:
Effective focal length is about 90mm and effective min aperture value is 1,6 Smile

I don't understand that. Do you apply some kind of focal reducer?

Nice samples BTW.


PostPosted: Thu Jan 22, 2015 11:27 pm    Post subject: Reply with quote
The lens is 150mm on 35mm and has the depth of field you'd expect for that focal length at f2.8. On the 645 body, the efective field of view represented in terms of 35mm focal length is a sub 1.0x multiplication, like aps-c is 1.5x, 645 medium format is around 0.6x. Therefore the equivalent depth of field of a 90mm lens is also shallower. (f1.6 in this case, though we don't get that much light in, just the equivalent depth of field) It's confusing as it's backwards to what we're used to with digital. My 80mm f1.9 is equivalent to a 50mm f1.2.


PostPosted: Mon Jan 26, 2015 1:54 am    Post subject: Reply with quote
Kei wrote:
The lens is 150mm on 35mm and has the depth of field you'd expect for that focal length at f2.8. On the 645 body, the efective field of view represented in terms of 35mm focal length is a sub 1.0x multiplication, like aps-c is 1.5x, 645 medium format is around 0.6x. Therefore the equivalent depth of field of a 90mm lens is also shallower. (f1.6 in this case, though we don't get that much light in, just the equivalent depth of field) It's confusing as it's backwards to what we're used to with digital. My 80mm f1.9 is equivalent to a 50mm f1.2.


That seems convoluted. Aperture is a measure related to light, not depth of field. A 150mm lens is 150mm regardless of what format it is used on, but since the old 35mm format was considered a standard, we use its field of view for offering comparisons when using smaller formats. Granted, the larger the format, the greater the field of view. Depth of field is similar in that you can make those "effective" comparisons, but the actual depth of field does not change. The depth of field as a portion of the image size is greater or more shallow as format size changes, but the depth of field does not change just like the focal length does not change, it's just perception. And f-stops are the same regardless of sensor size.


PostPosted: Mon Jan 26, 2015 3:24 am    Post subject: Reply with quote
woodrim wrote:
Kei wrote:
The lens is 150mm on 35mm and has the depth of field you'd expect for that focal length at f2.8. On the 645 body, the efective field of view represented in terms of 35mm focal length is a sub 1.0x multiplication, like aps-c is 1.5x, 645 medium format is around 0.6x. Therefore the equivalent depth of field of a 90mm lens is also shallower. (f1.6 in this case, though we don't get that much light in, just the equivalent depth of field) It's confusing as it's backwards to what we're used to with digital. My 80mm f1.9 is equivalent to a 50mm f1.2.


That seems convoluted. Aperture is a measure related to light, not depth of field. A 150mm lens is 150mm regardless of what format it is used on, but since the old 35mm format was considered a standard, we use its field of view for offering comparisons when using smaller formats. Granted, the larger the format, the greater the field of view. Depth of field is similar in that you can make those "effective" comparisons, but the actual depth of field does not change. The depth of field as a portion of the image size is greater or more shallow as format size changes, but the depth of field does not change just like the focal length does not change, it's just perception. And f-stops are the same regardless of sensor size.

The focal length and the f-number are the properties of a given lens and they are independent of the sensor format.

For a given focal length and the f-number:

Case A: when the sensor become larger and larger, the field of view will increase.

As a result of the increased field of view, the we need to move closer to the subject to get the exact framing as before. The decrease in focus distance will cause an decrease in depth of field.

Case B: when the sensor become smaller and smaller, the the field of view will decrease.

As a result of the decreased field of view, the we need to move farther from the subject to get the exact framing as before. The increase in focus distance will cause an increase in depth of field.


PostPosted: Mon Jan 26, 2015 10:33 pm    Post subject: Reply with quote
Calvin: We agree except I too a different approach in explaining the DOF. Although I have heard your explanation before, it just seems so elementary. Whenever you move closer to a subject, while inside of infinity focus, it is understood that the focus must change in the direction away from infinity, thus decreasing DOF. This in no way means a lens provides more or less DOF depending on format size, it's a function of focus. What I attempted to explain is a "perception" of DOF change, not none in reality.


PostPosted: Wed Jan 28, 2015 3:47 am    Post subject: Reply with quote
woodrim wrote:
Calvin: We agree except I too a different approach in explaining the DOF. Although I have heard your explanation before, it just seems so elementary. Whenever you move closer to a subject, while inside of infinity focus, it is understood that the focus must change in the direction away from infinity, thus decreasing DOF. This in no way means a lens provides more or less DOF depending on format size, it's a function of focus. What I attempted to explain is a "perception" of DOF change, not none in reality.

Yes, I think we are describing the same thing using different approach. And we have not include other factors affecting the DOF other than focus distance.


PostPosted: Wed Feb 18, 2015 5:09 pm    Post subject: Reply with quote
So, do we have consensus on that a 150/2.8 lens for the 645 system, is the equivalent to a 90/1.6 lens on a FF camera?

A Rose and The Window by Sigurd Ruschkowski, on Flickr


/SR


PostPosted: Wed Feb 18, 2015 6:46 pm    Post subject: Reply with quote
No, it's still a 2.8/150.


PostPosted: Thu Feb 19, 2015 1:04 am    Post subject: Reply with quote
Sigurd: I do know what you are saying about the focal length, but the speed of the lens - the max aperture - never changes and is not used to describe depth of field. The focal length adjustment you are making is just an angle of view thing that is different with each different size sensor. It became customary to offer a crop factor for smaller format (sensor) cameras as a way for people who were accustomed to 35mm to better understand the change in angle of view. It was just a way to relate. 35mm was considered the de facto standard. However, those that used larger formats understood the impact on angle of view and apparently did not need to relate it to 35mm. To my knowledge, the crop factor was never applied in the larger direction. And likewise, medium format lenses have not used crop factors when used on 35mm, mostly because 35mm is the de facto standard.

Those crop factors are just aids for people to adjust their perceptions. The focal length never changes from one format to another. The depth of field never changes either. However, the depth of field may appear greater when moving to a smaller sensor just because of the percentage of area in focus relative to the size of the sensor. The depth of field will "appear" greater, not less when moving to a smaller sensor. But the best approach is to refer to a lens as its stated focal length and stated max aperture.

Now Calvin is going to say the same thing differently.


PostPosted: Fri Feb 20, 2015 6:08 am    Post subject: Reply with quote
While I think more about this, and I think it is time to do the math (makes me understand it better), I post two other photos taken with the Mamiya 150/2.8 A mounted on EOS 5D3 FF sensor:

An Apple Among Circles by Sigurd Ruschkowski, on Flickr


--------

Colour Mix by Sigurd Ruschkowski, on Flickr


/SR


PostPosted: Fri Feb 20, 2015 11:54 am    Post subject: Reply with quote
Having done some reading on circles of confusion yesterday, you'd be surprised to hear that there is more depth of field available on a mamiya ZD (0.039cm) or pentax 645D (0.05cm) than there is on a FF D800 (0.03cm). Of course, this is the inverse of what I expected.

Not taken many more with this lens. (probably because I have so many lenses around the same length) Here are the few.

Taking a break by --Kei--, on Flickr

Ridgeway by --Kei--, on Flickr

Ridegway by --Kei--, on Flickr

Twmbarlwm by --Kei--, on Flickr


PostPosted: Fri Feb 20, 2015 4:09 pm    Post subject: Reply with quote
I quit trying to figure out crop sensor/film/FF jive. If I like what I see in the viewfinder I push the button. Then move on to the image. More time for taking photographs that way.


PostPosted: Mon Aug 03, 2015 11:21 am    Post subject: Reply with quote
Seems I've become a mamiya addict as I can't seem to use anything else now. Been using the 150 more than any other lens, it's essentially rendered both my 135 f2.8 and 180 f2.5 obsolete as it's just so fantastic at everything.

Wide open
Gull by Kyle, on Flickr

Gull by Kyle, on Flickr

Which Way? by Kyle, on Flickr


Stopped down a little.
Barn by Kyle, on Flickr

Wye Valley by Kyle, on Flickr

Austin Healey by Kyle, on Flickr



Used as a macro (EXT Ring No.3s)
Fly by Kyle, on Flickr

KMW_9823 by Kyle, on Flickr


PostPosted: Mon Aug 03, 2015 10:50 pm    Post subject: Reply with quote
One of the great lenses for sure.
You have some excellent results here
Thank you
OH


PostPosted: Mon Aug 03, 2015 10:57 pm    Post subject: Reply with quote
!966/67 Austin-Healey 3000 BJ8, nice. Yours?


PostPosted: Mon Aug 03, 2015 11:00 pm    Post subject: Reply with quote
It's a 150 f2.8 and remains so on a FF sensor.


PostPosted: Tue Aug 04, 2015 2:03 pm    Post subject: Reply with quote
woodrim wrote:
!966/67 Austin-Healey 3000 BJ8, nice. Yours?

No, sadly not. I have an old saab 900 turbo in a similar colour.


PostPosted: Tue Aug 04, 2015 2:56 pm    Post subject: Reply with quote
I'd take a Saab over a Healey any day!

My 900 Turbo has not once failed to start in 12 years and has never broken down, over 100,000 miles and still not had anything major replaced.


PostPosted: Tue Aug 04, 2015 7:37 pm    Post subject: Reply with quote
I agree with you, certainly wouldn't part with mine for something other than another saab. It'd be nice to have a classic like a healey as a second car though.

Is yours a classic (pre 1993) model? Mine is one of the new gen models, which is wearing well considering it's 20 years old and done 190,000 miles. Suffered from fuel pump failure last year at ~185k, first time it let me down.


PostPosted: Tue Aug 04, 2015 7:51 pm    Post subject: Reply with quote
Mine is a second gen too, I had two first gens before it. Not sure of the total mileage on mine now, it was at 78,000 when I got it and I think it's just over 200,000 now.

The good thing about the Healey is that they made if out of bits from the Austin parts bin so spare parts are common and cheap. The Healey Sprite is mostly Mini parts and that makes it comparatively cheap to run. Sprites are very popular with the hill climbers as they are so small and agile, albeit not very powerful, about the same as a Mini Cooper and those won plenty of rallies in the 60s. The Saab Sonnet is about the same size as the Sprite.


PostPosted: Wed Aug 05, 2015 10:48 pm    Post subject: Reply with quote
Lovely work. I was just perusing the mamiya sekor 645 lenses and there seems to be a bunch of them at quite inexpensive prices. Is it just a glut or are some of them not as good as others? I have several m42 and they seem to be pretty good.


PostPosted: Wed Aug 05, 2015 11:19 pm    Post subject: Reply with quote
jamaeolus wrote:
Lovely work. I was just perusing the mamiya sekor 645 lenses and there seems to be a bunch of them at quite inexpensive prices. Is it just a glut or are some of them not as good as others? I have several m42 and they seem to be pretty good.


There are no really bad ones and most are very good to excellent.
I think that the "less sharp" are in the wider angle range, so no real sense in trying to adapt them to APSC or even full frame digital in any case, as there are smaller and better lenses around.
From the 80mm upwards all are very good or excellent.
The A lenses are truly superb of course.
Well worth exploring.
OH
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