Crop factor for Pentax 67 lenses?

[Billy Jim]

....as an owner of a fully modded set of Hasselblads, i have found their bokeh to be quite unique and alluring. They have their own personailty, quite different than my Contax, even on the same sensor.

Any chance you could post some side by side examples?

 

[Timur Civan]

There is no such thing as crop factor. Perpetuating the phrase please.

Just know your format, and the lenses FOV in accordance to that format.

 

[Todd T]

So then the OP's question should have been:

What is the general ratio of the difference in the the field of view of any lens of a particular focal length between a Pentax 67 size sensor and an Epic size sensor?"

[Ducks behind Desk...]

 

[Maik Müller]

Hehehe, funny thread.

"A fifty is a fifty..."

It just reminds me, a focal reducer for Medium-Format lenses would be something interesting to explore

 

[Ketch Rossi]

it applies here too:

Guys....

Simple answer has been given... A 50mm is and will always be and remain a 50mm Lens, NO matter were or on what you place that lens!!

HOWEVER...

If a 50mm Lens design for FF 24x36 sensor such as the 5D, and used on a x1.3 cropped sensor camera such as the Red One, or Epic MX (eta just make strait mathematical example without going in to inner decimals) then such a 50mm while remaining a 50mm will give you an image equal in field of view of that of a 65mm, and that is a FACT...

HOWEVER...

What this means is not that magically your 50mm (based it is a still lens form FF 24x36 sensor) has turned in to a 65mm... (based on the 1.3 Red One MX Y Red Epic MX sensor size vs FF).

What it means is that you placed that 50mm in a sensor smaller then the one that the 50mm was designed for, and here is why you get the image that is smaller in the frame and appears as if it is a 65mm, because it is only using the center of the lens and not all of the lens it can be a blazing or a curse depending on how you see it, as some like the look of the edges on a given lens.

Additionally, there is an other element to consider strongly here...

A Focal is used and chosen not only because of the area it needs to cover in the frame, but also it is or at list it should be also a choice carefully considered as to display on screen what the Director/DP Photographers wishes to display as to convey not only the Image itself but also the fill that it contains, were the wider the lens the more distance each subject appear form each other and differentiation is made by that which is the Foreground form the Background.

So, you need to make subjects appear much closer to each other then they really are, or much closer to the background then they really are... Then you use a Longer Focal and move the camera further out... If you need the opposite then move the camera closer and use a Wider lens.

But when all you have is what you have and can no take this creative choices, then just use what you have that gives you the framing you want, and don't worry or over worry too much about Crop factor on a lens, because lenses don't have a crop factor!!


BTW... On this last words... I like to think that a 200 1.8 & 2.0 are great lenses and had both of them in the Canon mount, but the Canon or RPP 300mm 2.8 range it is just magical and an other great lens, so choosing which to use only based on the speed or Focal without knowing any needs for the character of the image at hand would be limiting, and if I had to choose only ONE either way, I would as I have already choose the RPP 300mm 2.8 every time...

But each one's opinion I am sure will continue to vary as it comes down to also a matter of taste, not just reach of the lens or speed.

 

[Bill Anderson]

My son just picked up a GH4 and asked, "hey dad, I'm trying to figure out which lenses to get, what is the crop factor to find the Full Frame equivalent FOV?"
I could have said, son, there is no such thing as a crop factor, you just have to know your lenses on any given format, but I didn't, I gave him the simple formula
that shows lens FOV equivalents between MFT and FF. And now he is off to the races and confidently buys the focal lengths he wants. But then he noticed,
"hey, if I have to use a 24mm lens to equal a 50mm FOV on full frame, then I'm stuck with the 24mm depth of field characteristics, and that combo is not really ideal".
So I pointed to the Speedbooster and explained that he could use a 50mm lens while retaining the same FOV as the 24mm (without S/booster) AND enjoy the depth of field characteristics
of the 50mm focal length. So now he's just tested two methods on MFT sensor, one shot with 24mm lens, and the other with S/booster and 50mm lens, and, while the FOV is
much the same for both combos, the DOF differs enough for him to realize the usefulness of having these choices. What a good dad, huh. ( :

 

[Maik Müller]

What a good dad, huh. ( :

As long as you have paid for the stuff.

 

[Ulf Krentz]

My son just picked up a GH4 and asked, "hey dad, I'm trying to figure out which lenses to get, what is the crop factor to find the Full Frame equivalent FOV?"
I could have said, son, there is no such thing as a crop factor, you just have to know your lenses on any given format, but I didn't, I gave him the simple formula
that shows lens FOV equivalents between MFT and FF. And now he is off to the races and confidently buys the focal lengths he wants. But then he noticed,
"hey, if I have to use a 24mm lens to equal a 50mm FOV on full frame, then I'm stuck with the 24mm depth of field characteristics, and that combo is not really ideal".
So I pointed to the Speedbooster and explained that he could use a 50mm lens while retaining the same FOV as the 24mm (without S/booster) AND enjoy the depth of field characteristics
of the 50mm focal length. So now he's just tested two methods on MFT sensor, one shot with 24mm lens, and the other with S/booster and 50mm lens, and, while the FOV is
much the same for both combos, the DOF differs enough for him to realize the usefulness of having these choices. What a good dad, huh. ( :

Wow, now we´ve drifted far... While the question of your son was precise in the first place you gave him the right answer.

But regarding the second option he could have replied, that the 50mm lens with the Speedbooster actually is part of a new system that has a focal length of 24mm. As this also increases the speed of this lens by one stop he understands the different DOF (if he sets his lens to f4 for example he actually uses f2,8 with that new lens combo, it´s not the characeristics of a 50mm lens.) Thanks for giving me this choices, Dad!

Cheers, Ulf

 

[Mark Toia]

I shoot with rehoused 6x6 Hasselblad Ziess and 6x7 Mamiya Medium format glass on my EPIC through a tilt shit setup.

I can tell you from a coverage stand point, I can turn and twist the lenses to almost 35 degrees any direction before they start to vignette.

From a crop factor point of view (or vignette) what ever you want to call it, some of the longer lenses look ike they will cover at least 9x a super 35mm sensor without any problems at all. so if you did your math... that's ... ??.. uumm..... 18k?


Oooh.... and I'm quite sure a 100mm is a 100mm when being shot onto a 35mm surface, but... for some reason, the 25mm Hasslblad ziess 6x6 lens we use looks like a 35mm when you have it on... ? and th3 35mm looks like a 50 and so on....
Which sort of throws a curve ball into this thread.

 

[Bill Anderson]

Given the possibility of larger sensors and the fact that they will render useless many cine lenses designed to cover S35, and possibly full frame for that matter, would it be feasible to make a sort of reverse type "speedbooster" that would allow these otherwise unusable lenses to cover a larger sensor? I know this somewhat defeats the beauty of a larger sensor with an optimum lens (not to mention Mark's solution) however, would the results still not be worthwhile as an alternative to obsoleting so much good glass? Doable?

 

[Jeff Kilgroe]

Oooh.... and I'm quite sure a 100mm is a 100mm when being shot onto a 35mm surface, but... for some reason, the 25mm Hasslblad ziess 6x6 lens we use looks like a 35mm when you have it on... ? and th3 35mm looks like a 50 and so on....
Which sort of throws a curve ball into this thread.

There are always optical differences between lens designs and even variances within those designs or their respective mounting systems. It's not uncommon to see slight variances in AOV between two lenses of the same make and model and focal length. And even more so between those from different makers. A lot of this comes down to the spherical (or aspherical) design of the lens and how well it controls distortions, breathing, etc..

I think one thing that can be learned from this thread is that crop factor thinking is evil and has become a cancer within the photography and cinematography industries.

It seems to me that in an effort to simplify the concept for the enthusiast or casual photographer, the camera manufacturers have over-complicated the heck out of it.

 

[Nick Morrison]

Oooh.... and I'm quite sure a 100mm is a 100mm when being shot onto a 35mm surface, but... for some reason, the 25mm Hasslblad ziess 6x6 lens we use looks like a 35mm when you have it on... ? and th3 35mm looks like a 50 and so on....
Which sort of throws a curve ball into this thread.

Hmmm...my guess Mark is that the 25mm and 35mm have been modified. Traditionally, the widest Hasselblad Full Frame lens I believe is a 40mm (equivalent to 17mm in Super 35). They made a 30mm, but that was a fisheye. Perhaps these are a 40mm and 50mm with some kind of wide-angle element attached? Hmmm...very curious indeed!

 

[Mark Toia]

Hmmm...my guess Mark is that the 25mm and 35mm have been modified. Traditionally, the widest Hasselblad Full Frame lens I believe is a 40mm (equivalent to 17mm in Super 35). They made a 30mm, but that was a fisheye. Perhaps these are a 40mm and 50mm with some kind of wide-angle element attached? Hmmm...very curious indeed!

Actually... your dead right

 

[Nick Morrison]

Actually... your dead right

Haha. We all get lucky sometimes.

 

[Maik Müller]

Given the possibility of larger sensors and the fact that they will render useless many cine lenses designed to cover S35, and possibly full frame for that matter, would it be feasible to make a sort of reverse type "speedbooster" that would allow these otherwise unusable lenses to cover a larger sensor? I know this somewhat defeats the beauty of a larger sensor with an optimum lens (not to mention Mark's solution) however, would the results still not be worthwhile as an alternative to obsoleting so much good glass? Doable?

In general, thats what teleconverters do, just not with that specific scenario in mind. They do enlarge the center-area of a lens to cover the full sensor. I don't see a reason why there couldn't be a converter that uses the full lens to cover a bigger sensor.

And if i remember correctly, something like this has already been announced, i think it was a PL-adapter that makes S35-lenses compatible with the bigger Dragon. I can't find it right now and don't remember the name, but it did go into that direction.

 

[D Fuller]

Haha. We all get lucky sometimes.

Don't ever mistake knowledge for luck.

 

[Todd T]

... I don't see a reason why there couldn't be a converter that uses the full lens to cover a bigger sensor.

Two reasons to consider would be the loss in optical quality and loss of light due to additional optic elements needed to adjust the size of the image circle, and the other would be the number of stops of light lost inherently by increasing the size of the image circle.

Just as an absurd example , such an adapter would turn your 50mm T1.4 lens into a T5.6.

 

[Nick Morrison]

Any chance you could post some side by side examples?

I don't have side by sides, but here's a spot shot on a Hassy 80 2.8, tilted. You can see the colorful bokeh in the background. Full of gorgeous swirls not found on my Contax primes:

 

[Maik Müller]

Two reasons to consider would be the loss in optical quality and loss of light due to additional optic elements needed to adjust the size of the image circle, and the other would be the number of stops of light lost inherently by increasing the size of the image circle.

All true, but its possible and maybe useful for a few or even a lot of lenses.

People use those 2x extenders quite a lot and todays lenses have some unused resolving power left.