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Anyone try a Pentax 67 105f2.4 on any fullframe DSLR?
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PostPosted: Sat Jan 13, 2018 9:54 pm    Post subject: Anyone try a Pentax 67 105f2.4 on any fullframe DSLR? Reply with quote

Im loving my Jupiter 36B 250 F3.5 on my A7R2...the shallow depth of field and its corner to corner sharpness are very nice. It has a little CA but correctable in post processing. It also serves as a great personal defense weapon, as well as a portable gym. will be a blast to shoot at my sons soccer games next year...

Given the outstanding reputation of the Pentax 67 105F2.4, has anyone shot it on full frame? I believe it might be an unbelievable portrait lens for under $300 with adapter. (its DOF is the equivalent of a 1.2ish native. my go to portrait now is a zeiss 85 2.8 planar.

Thoughts?


PostPosted: Sat Jan 13, 2018 10:13 pm    Post subject: Re: Anyone try a Pentax 67 105f2.4 on any fullframe DSLR? Reply with quote

Gatorengineer64 wrote:

...
its DOF is the equivalent of a 1.2ish native. my go to portrait now is a zeiss 85 2.8 planar.

Thoughts?


The lens is a 2.4/105mm, and it will act as an 2.4/105mm also on 24MP FF. Certainly not like a f1.2 lens ...

Stephan


PostPosted: Sat Jan 13, 2018 10:22 pm    Post subject: Reply with quote

There is a ton of mis-information, but a MF lens shoots roughly life a ff lens three stops faster only FROM a depth of field standpoint. It will still shoot from an exposure standpoint like its native, but for isolating a subject that is where the strength of medium format on FF is. Also I cant think of a 250 F3.5 on Full frame that can be had for the price of a kiev 88 MF lens. you can google it or use F calc.

http://fcalc.net/


PostPosted: Sat Jan 13, 2018 11:54 pm    Post subject: Reply with quote

"a MF lens shoots roughly life a ff lens three stops faster only FROM a depth of field standpoint."

But that's only if you are shooting 120 film.
The real advantage of an MF lens is it projects a much larger image out the back, so you can use a large film.

Lets assume you have a Pentax 67 (6x7cm on 120 film), and a Pentax K1 (FF digital) and are shooting head and shoulders portraits.

MF lets you use a longer FL for the same subject at the same distance - a 105mm instead of a 50mm on the FF digital.

Or if using a 105mm on both cameras, you can stand closer to the subject.

Both will give you shallower DOF.

But there is no difference at all between an MF 105 and an FF 105 if you are using them both on an FF digital sensor.


PostPosted: Sun Jan 14, 2018 12:13 am    Post subject: Reply with quote

luisalegria wrote:
"a MF lens shoots roughly life a ff lens three stops faster only FROM a depth of field standpoint."

But that's only if you are shooting 120 film.
The real advantage of an MF lens is it projects a much larger image out the back, so you can use a large film.

Lets assume you have a Pentax 67 (6x7cm on 120 film), and a Pentax K1 (FF digital) and are shooting head and shoulders portraits.

MF lets you use a longer FL for the same subject at the same distance - a 105mm instead of a 50mm on the FF digital.

Or if using a 105mm on both cameras, you can stand closer to the subject.

Both will give you shallower DOF.

But there is no difference at all between an MF 105 and an FF 105 if you are using them both on an FF digital sensor.


Oh Luis, how often do we both have to repeat "a 105 is a 105 is a105 is a 105...", I feel like a Tibetian monk at times... Twisted Evil


PostPosted: Sun Jan 14, 2018 12:23 am    Post subject: Reply with quote

You are of course completely right, except when it comes to DOF.... You cant "crop" out depth of field, its not a function of the distance from the center of frame. We agree that a MF has a deeper Depth of field, now when you only take part of that frame, you are still taking the whole DOF with it. if that makes sense. I dont have anything native at 250MM to compare it to, but if I get the Pentax, I will post something close to illustrate. Its also readily googleable.


PostPosted: Sun Jan 14, 2018 3:19 am    Post subject: Reply with quote

Using a 105mm lens on a APS-C/135 format camera is 'exactly' equals to cropping the center part of the photo taken by a MF or LF camera.


PostPosted: Sun Jan 14, 2018 10:36 am    Post subject: Reply with quote

kds315* wrote:
Oh Luis, how often do we both have to repeat "a 105 is a 105 is a105 is a 105...", I feel like a Tibetian monk at times... Twisted Evil

Me too ...

Gatorengineer64 wrote:
You are of course completely right, except when it comes to DOF....

Sorry, you're wrong - as long as you are talking about using both lenses (medium format and native FF lens) on a FF camera.

I will take some images with the Mamyia Sekor C 1.9/80mm and with the Minolta AF 1.4/85mm, as well as with the Mamyia Sekor C 4/210mm and the Minolta AF 2.8/200mm. According to your theory, the background should be much more blurred when using the Mamiya lenses. According to my knowledge, the background will be essentialy the same when using the same aperture, and being more blurred with the Minolta FF lenses, when using all lenses wide open.

There will be small differences concerning the e. g. the shape of highlights (soft, disk-like, or donut shaped). These are a result of the under- or overcorrection of sperical aberration (called "bokeh").


Gatorengineer64 wrote:

We agree that a MF has a deeper Depth of field,

A few hours ago ago you said exactly the contrary.

I'm telling you that both your opinions are wrong if you use both lenses (medium format and full frame) on a full frame body.

The general opinion that a 105mm lens @f2.4 on 6x7cm film results the same image as a 52.5mm @f1.2 lens on full frame, however, is correct.

Gatorengineer64 wrote:

now when you only take part of that frame, you are still taking the whole DOF with it. if that makes sense. I dont have anything native at 250MM to compare it to, but if I get the Pentax, I will post something close to illustrate. Its also readily googleable.

Start exploring reality before explaining reality to others Wink ...


PostPosted: Sun Jan 14, 2018 10:54 am    Post subject: Reply with quote

Save your precious time Stephan, I would not do that. Why would you need to prove someone wrong,
let them just make their own experience, they won't learn it otherwise. Only own mistakes makes one
learn. Until one haven't put one's hand on a hot stove top, all talking is in vain. Once done, you never
forget!! And no talking is needed anymore Twisted Evil My grandpa always said that, and right he was.


PostPosted: Sun Jan 14, 2018 10:56 am    Post subject: Reply with quote

Gatorengineer64 wrote:
There is a ton of mis-information, but a MF lens shoots roughly life a ff lens three stops faster only FROM a depth of field standpoint. It will still shoot from an exposure standpoint like its native, but for isolating a subject that is where the strength of medium format on FF is. Also I cant think of a 250 F3.5 on Full frame that can be had for the price of a kiev 88 MF lens. you can google it or use F calc.

http://fcalc.net/


If you get a medium format speed booster like this http://www.kipon.com/en/articledetail.asp?id=97 then you would make a lot more sense.


PostPosted: Sun Jan 14, 2018 11:02 am    Post subject: Re: Anyone try a Pentax 67 105f2.4 on any fullframe DSLR? Reply with quote

Gatorengineer64 wrote:

I believe it might be an unbelievable portrait lens for under $300 with adapter. (its DOF is the equivalent of a 1.2ish native. my go to portrait now is a zeiss 85 2.8 planar.

Thoughts?


If my thinking is correct Gatorengineer64, while it may still make a good portrait lens, it will be less effective at this when projecting on to a full frame sensor. The issue is depth of field.

The properties of a medium format lens do not change when put on a full frame camera, however, how the photographer takes a shot using the lens does tend to change.

A full frame sensor will take a crop of the image the medium format lens is projecting into the camera (and your viewfinder). So, to fill the frame with the amount of subject you want, the photographer will position the camera further away in comparison to using a medium format camera. Standing further away will produce a greater depth of field.

The above is just me thinking it through. It could be that, in spite of this, the lens still takes a good traditional style portrait. It would be interesting to see a real world test.

And of course narrow depth of field, while the traditional route to a satisfying portrait, isn't the only route. I recently posted a 'portrait' of my motorcycle on the site, where I'd set the subject slightly out of focus and the background in focus. It seemed to work for what I wanted to express.

If my thinking is wrong here, I'm more than happy to be corrected. We all stay on a learning curve for our lives. And I'm only on my first coffee of the morning.


Last edited by Sciolist on Sun Jan 14, 2018 11:18 am; edited 1 time in total


PostPosted: Sun Jan 14, 2018 11:15 am    Post subject: Re: Anyone try a Pentax 67 105f2.4 on any fullframe DSLR? Reply with quote

Sciolist wrote:
Gatorengineer64 wrote:

I believe it might be an unbelievable portrait lens for under $300 with adapter. (its DOF is the equivalent of a 1.2ish native. my go to portrait now is a zeiss 85 2.8 planar.

Thoughts?


If my thinking is correct Gatorengineer64, while it may still make a good portrait lens, it will be less effective at this when projecting on to a full frame sensor. The issue is depth of field.

The properties of a medium format lens do not change when put on a full frame camera, however, how the photographer takes a shot using the lens does tend to change.

A full frame sensor will take a crop of the image the medium format lens is projecting into the camera (and your viewfinder). So, to fill the frame with the amount of subject you want, the photographer has to position the camera further away in comparison to using a medium format camera. Standing further away increases the depth of field produced by the lens.

The above is just me thinking it through. It could be that, in spite of this, the lens still takes a good traditional style portrait. It would be interesting to see a real world test.

If my thinking is wrong here, I'm more than happy to be corrected. We all stay on a learning curve for our lives. And I'm only on my first coffee of the morning.


You got this right.

And I think the 105mm 2.4 would still be a good portrait lens on fullframe. I'm looking for one to try out actually. But there is always the risk of low contrast due to the big image circle/old coatings/adapter design.

I have tested a MC Volna 3 80mm medium format lens on my Sony a7 and the contrast was very poor. But on a 6x6 Kiev 60 that issue was gone.

If you really want to use medium format lenses I recommend 645 lenses. I have a few for Mamiya, they are not much bigger or heavier than FF lenses.

The Mamiya 645 A 150mm 2.8 has very good performance on my Sony. But this one has some weight.


PostPosted: Sun Jan 14, 2018 11:26 am    Post subject: Reply with quote

blotafton wrote:
Gatorengineer64 wrote:
There is a ton of mis-information, but a MF lens shoots roughly life a ff lens three stops faster only FROM a depth of field standpoint. It will still shoot from an exposure standpoint like its native, but for isolating a subject that is where the strength of medium format on FF is. Also I cant think of a 250 F3.5 on Full frame that can be had for the price of a kiev 88 MF lens. you can google it or use F calc.

http://fcalc.net/


If you get a medium format speed booster like this http://www.kipon.com/en/articledetail.asp?id=97 then you would make a lot more sense.


Indeed. The obvious practical way to change the properties of a lens is to add another lens to it, as you do with a speed booster.


PostPosted: Sun Jan 14, 2018 1:51 pm    Post subject: Reply with quote

At the same aperture, changing the subject distance changes the dof. Comparing any cameras, any lenses, any focal lengths.

Put another way, at the same aperture, keeping the subject distance constant, dof is identical because subject distance does not change.

I think Gatorengineer64 is referring to the table on page 10 of "Depth of Field and Bokeh by H. H. Nasse" which causes much confusion unless the test conditions leading to the table are well understood, imho.

http://lenspire.zeiss.com/en/wp-content/uploads/sites/2/2016/03/cln35_en_web_special_bokeh.pdf

Dof is a function of aperture and magnification. Magnification is a function of focal length and subject distance and sensor size. Maybe it's easier to think of Magnification as framing.

Please correct me if I'm wrong!!!


PostPosted: Sun Jan 14, 2018 2:12 pm    Post subject: Reply with quote

@visualopsins
Magnification = image size/object size. It has nothing to do with sensor size.


PostPosted: Sun Jan 14, 2018 2:38 pm    Post subject: Reply with quote

"We agree that a MF has a deeper Depth of field,"

Yes I got this backwards, (at the time greater in my pea sized brain meant better for portraits, but yes, I had it backwards, and it made me sound like an idiot).

I stand by what I say and what I have read, you cant crop depth of field and a MF lens has a shallower Depth of field than a FF, because it is illuminating a larger sensor (film being a sensor). In astronomy Magnification is exit pupil over focal length, with exit pupil being the sensor, you double the sensor, you have to double the FL for a given magnification (angular field of view whatever), but the DOF does change. Part of the medium format look is that shallower DOF.

Im hoping some here that have the gear can post some examples. The only two Kiev-88s I have are a fisheye and the 250, and I cant match either in full frame.


PostPosted: Sun Jan 14, 2018 2:43 pm    Post subject: Reply with quote

You can set your camera to APS-C mode....


PostPosted: Sun Jan 14, 2018 2:54 pm    Post subject: Reply with quote

I don't know if it will make anyone wiser but here is a comparison made by Tim https://www.flickr.com/photos/tb303/2884286769

Hasselblad Planar 80mm 2.8 vs EOS 5D Distagon 35mm 1.4.


PostPosted: Sun Jan 14, 2018 3:03 pm    Post subject: Reply with quote

Do you mind if I complicate it even more? 120 film is usually enlarged less than 35 mm. Depth of field does not really exist, I understand. A lens is only fully sharp at one set distance. Depth of field has something to do with "circles of confusion?" Depth of field on a lens is based on a certain enlargement of the negative, viewing the print at a certain distance and the sharpness than perceived. According to this, wouldn't a 120 film lens have a wider depth of field than a 35 mm?


PostPosted: Sun Jan 14, 2018 3:36 pm    Post subject: Reply with quote

Evert wrote:
Do you mind if I complicate it even more? 120 film is usually enlarged less than 35 mm. Depth of field does not really exist, I understand. A lens is only fully sharp at one set distance. Depth of field has something to do with "circles of confusion?" Depth of field on a lens is based on a certain enlargement of the negative, viewing the print at a certain distance and the sharpness than perceived. According to this, wouldn't a 120 film lens have a wider depth of field than a 35 mm?


Yes, depth of field is the plane which an individual perceives to be in focus. This is due to us not recognising the effect of circular light rays (circles of confusion), as portrayed on an image, below a certain size. However, if you blow an image up sufficiently (thus making that light ray big enough), that which would normally look in focus, can appear as a blurry mess and not 'in-focus' at all.



I wish they'd chosen something better than 'circle of confusion' as a term, but I'm sure there is a reason for it.

The above explanation is about right I think (I'm not completely happy with it), but I'm using brevity to explain something that probably needs an essay.


PostPosted: Sun Jan 14, 2018 4:17 pm    Post subject: Reply with quote

calvin83 wrote:
@visualopsins
Magnification = image size/object size. It has nothing to do with sensor size.


Thanks calvin83!

image size/object size, yes!!! However same size prints will show the object smaller for larger format. I now see I confuse magnification with framing in my explanations.


PostPosted: Mon Jan 15, 2018 4:15 am    Post subject: Reply with quote

All this nonsense about lenses having a "variable focal length" according to the size of the sensor/film is a consequence of the use and abuse of "equivalence" on internet forums.

I have a 50mm F/5.6 superwide on my Fuji 6x9 rqngefinder camera. According to commun internet knowledge, it is "equivalent" to a 21mm lens on the 24x36 sensor of my Sony A7, to a 14mm lens on the APS-C sensor of my Sony A6000, to a 10.5mm lens on the M4/3 sensor of my Olympus E-P1 and to a 4.57mm lens on the tiny 1/1.7' sensor of my Pentax Q-S1. But this is not what I experience when I use this lens on 6x9, and the results certainly don't look the same to me!

Why do we have to use all these confusing values and could not stick to the diagonal angle of view as a measure of a lens' field of view on a given sensor/film size? For example, this particular Fuji lens on 6x9 has a diagonal angle of view of approximately 91°, and so does a 21mm lens on 24x36, a 14mm lens on APS-C, and so on. It is not particularly difficult to memorize the angle of view of usual lenses, and if everybody did that, we would not have to cope with these confusing "equivalent focal lengths" and their associated conversion tables. 90° is a superwide, 50° is a standard lens and 8° is a super-tele. Easy. But a 50mm lens is not a 21mm lens.

It becomes even more confusing IMHO when people start talking about "equivalent aperture" and "equivalent ISO value". As a consequence, the internet forums are full of people who really believe that a 25mm F/1.4 lens on M4/3 is the same as a 50mm F/2.8 lens on 24x36, therefore requiring two more stops of light than a 50mm F/1.4 on 24x36. When you prove them wrong buy shooting the same picture at 50mm with the same aperture/speed/ISO combination both on a 24x36 sensor and an M4/3 sensor, they tell you that the manufacturers cheat on the ISO value of smaller sensor cameras!

Meanwhile, I continue to enjoy my big 6x9 Fuji for portrait, because it shines with its 180mm short tele, and the results do not at all look like pictures taken with a 75mm lens on a 24x36 camera. And I prefer the diminutive Q-S1 with its small 1/1.7" sensor for macro work and extreme telephoto. Even for landscape work, the Q-S1 with its miniature 3.8mm wide angle is certainly no slouch. And it delivers pictures that are not "equivalent" to those of a Tamron 17mm lens on 24x36 (this picture has not been sharpened; click to view it at 100% and look at the lower left and right corners):



Cheers!

Abbazz


PostPosted: Mon Jan 15, 2018 11:32 am    Post subject: Reply with quote

Abbazz wrote:
All this nonsense...


I'd agree Abbazz.

However, while it continues with people on the internet, it's source is not from them from what I've perceived. The source, I suspect, were marketing departments trying to help film photographers transition to digital. I suspect that if the marketing guys had spoken to the engineering department, we may indeed have been using field of view as the common comparison. Instead, and only a gut feeling, the marketing guys spoke to each other about how best to explain these new sensor sizes to film photographers, and came up with 'equivalence'. This in turn was promoted to retail and camera reviewers as talking points, who in turn talked about it on the internet. Taking this lead, it became the common comparison on the internet.

That's my guess anyway.

It would be interesting to see what comparators were used, if any, in the film world back in the day, when a new film size came on the market.


PostPosted: Mon Jan 15, 2018 1:08 pm    Post subject: Reply with quote

Sciolist wrote:
Abbazz wrote:
All this nonsense...


I'd agree Abbazz.

However, while it continues with people on the internet, it's source is not from them from what I've perceived. The source, I suspect, were marketing departments trying to help film photographers transition to digital. I suspect that if the marketing guys had spoken to the engineering department, we may indeed have been using field of view as the common comparison. Instead, and only a gut feeling, the marketing guys spoke to each other about how best to explain these new sensor sizes to film photographers, and came up with 'equivalence'. This in turn was promoted to retail and camera reviewers as talking points, who in turn talked about it on the internet. Taking this lead, it became the common comparison on the internet.

That's my guess anyway.

It would be interesting to see what comparators were used, if any, in the film world back in the day, when a new film size came on the market.


I agree to both of you.

Many of the modern digital cameras with smaller than 24x36 sensors have the focal length field of view equivalence already marked on their lenses. E.g. my old Minolta Dimage 7i with 8.8 x 6.6 mm sensor doesn't even state the actual focal length but only "28 - 200 mm" which is absolute nonsense. Also my Ricoh GXR APS-C modules are sold as 28mm (actual 18.3mm) and 50mm (actual 33mm) ones and there are many others as well. Therefore the source is undoubtfully the camera industry itself.


Last edited by tb_a on Mon Jan 15, 2018 3:24 pm; edited 1 time in total


PostPosted: Mon Jan 15, 2018 1:45 pm    Post subject: Reply with quote

blotafton wrote:
I don't know if it will make anyone wiser but here is a comparison made by Tim https://www.flickr.com/photos/tb303/2884286769

Hasselblad Planar 80mm 2.8 vs EOS 5D Distagon 35mm 1.4.

Again photos says more then thousands words Wink, nice share!