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Hasselblad X system crop factor

L

larkis

Member
I have run across a video featuring Hasselblad's technical communications manager
where (at 45:30) he shows a chart claiming the 30mm lens is a 21mm FF equivalent, while there is another website here Hasselblad X System Crop Factor and XCD Lens Full Frame Equivalent Focal Lengths (shuttermuse.com) which shows the math and arrives at basically 24mm. Which information is correct here?

Hasselblad shows 24mm in their marketing so maybe the tech communications manager was putting together the chart after a strong beverage?
 
tenmangu81

tenmangu81

Well-known member
Be careful, as FF is 24x36 (3:2), and Hasselblad X is 33x44 (4:3). They are not homothetic, and all depends upon which dimension you consider : diagonal, long edge, short edge ?
 
darr

darr

Well-known member
Robert is correct as the aspect ratios/proportions are not the same in (3:2) vs (4:3).
In terms of field of view, the 3:2 ratio offers a wider composition, while the 4:3 ratio tends to provide more vertical space relative to the width.

--

To arrive at the full-frame (FF) equivalence of the Hasselblad XCD 30mm, you would need to account for the crop factor of the medium format sensor (4:3) compared to an FF sensor (3:2). The X1D, or 907X, has a sensor size ≈ 44mm x 33mm and the crop factor relative to a 35mm FF sensor (36mm x 24mm) is approximately 0.79. This means that to find the FF equivalent focal length, you multiply the focal length of the XCD lens by the crop factor.

Here’s how you would calculate the full-frame equivalence:
  1. 30mm XCD lens:
    FF equivalent = 30mm * 0.79 ≈ 23.7mm
  2. 24mm XCD lens (hypothetically):
    FF equivalent = 24mm * 0.79 ≈ 19mm

So, a 30mm XCD lens would be *roughly* equivalent to a 24mm full-frame lens, and if there were a 24mm XCD lens, it would be about equivalent to a 19mm full-frame lens.

If you wanted an equivalence of 21mm on a full-frame sensor, you’d need an XCD lens of around 26.6mm (21 ÷ 0.79). However, since lens sizes don't always come in exact focal lengths, the closest XCD lens to give you approximately 21mm FF equivalence would be between 24mm and 30mm. :)
 
Godfrey

Godfrey

Well-known member
I don't have a tool of my own. I use Rui Salgueiro's field-of-view calculator ... for example...

XCD 30 on 33x44mm format sensor:
Width = 33 mm, Length = 44 mm, Diagonal = 55 mm
f Hor Vert Diag H/V
30 72.5077 57.6216 85.0209 1.2583

Various focal lengths on 24x36mm sensor:
Width = 24 mm, Length = 36 mm, Diagonal = 43.2666 mm
f Hor Vert Diag H/V
20 83.9744 61.9275 94.4932 1.3560
21 81.2026 59.4898 91.7021 1.3650
22 78.5788 57.2209 89.0370 1.3733
24 73.7398 53.1301 84.0622 1.3879
28 65.4705 46.3972 75.3806 1.4111
35 54.4322 37.8493 63.4400 1.4381

So if you're looking to find what 35mm lens the XCD 30mm matches in horizontal, vertical, or diagonal Angle of View, just look through the list in the AoV dimension important to you. You can see on the horizontal it is somewhere between a 28 and 35 mm equivalent, on the vertical it's very close to 22 mm, and on the diagonal it's between 22 and 24 mm AoV.

All together, I can't see how you'd call it a "21mm equivalent" at all.

G
 
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mristuccia

mristuccia

Well-known member
If you do the math considering the sensors' short side you'd approach 21mm.

24 / 33 = 0.727

30 * 0.727 = 21.81

But as already stated that's a bit if a stretch...
 
D

dougpeterson

Workshop Member
That’s the point of a visualizer though; depending on what/how you shoot the short, long, or diagonal may be the most appropriate comparison.

When I shot weddings a vertical portrait was my frame of reference (pun intended). I tended to crop those to 3:4 or even 4:5 anyway, so the long side or diagonal of a small format camera was a useless point of reference in my case - only the short side mattered.

A visualizer also helps remind you not to sweat small differences. 80mm vs 85mm may intuitively feel significant and may well be revealed to be something you don’t care about when you see the actual framing difference on a real image. Likewise 15mm vs 18mm may feel minor numerically and then be revealed to be significant to you when you see an actual image.

We are photographers. We are visual. It’s best to show an answer rather than calculate a number - at least for most of us.
 
B

bags27

Active member
While we're on this--and I apologize for piggybacking here--I'm always confused in reverse. If I put (say) an old V 80mm on my 907x, it's reverse, right? It "adds" length to the digital sensor, so it's effectively shooting around 100mm equivalent X lens. And then I have to "shrink" that number to figure out its FF equivalent. So it's back to around 75 FF equivalent? Right? or maybe wrong? or dumb really dumb way to do it?
 
tenmangu81

tenmangu81

Well-known member
I guess all depends upon the focal length of the lens, which is one of its physical characteristics (and the main one), and the dimensions of the sensor. Nothing more.
 
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rdeloe

rdeloe

Well-known member
bags27 said:
While we're on this--and I apologize for piggybacking here--I'm always confused in reverse. If I put (say) an old V 80mm on my 907x, it's reverse, right? It "adds" length to the digital sensor, so it's effectively shooting around 100mm equivalent X lens. And then I have to "shrink" that number to figure out its FF equivalent. So it's back to around 75 FF equivalent? Right? or maybe wrong? or dumb really dumb way to do it?
Click to expand...
If you put an 80mm lens on your 907x, it's an 80mm lens. There is no difference between an old V 80mm lens and an X 80mm lens (if such existed).
 
Godfrey

Godfrey

Well-known member
bags27 said:
While we're on this--and I apologize for piggybacking here--I'm always confused in reverse. If I put (say) an old V 80mm on my 907x, it's reverse, right? It "adds" length to the digital sensor, so it's effectively shooting around 100mm equivalent X lens. And then I have to "shrink" that number to figure out its FF equivalent. So it's back to around 75 FF equivalent? Right? or maybe wrong? or dumb really dumb way to do it?
Click to expand...
rdeloe said:
If you put an 80mm lens on your 907x, it's an 80mm lens. There is no difference between an old V 80mm lens and an X 80mm lens (if such existed).
Click to expand...
XCD 80... https://www.bhphotovideo.com/c/prod...ad_cp_hb_00000384_01_xcd_80mm_f_1_9_lens.html
But @rdeloe is exactly right: A V-system Zeiss Planar 80mm f/2.8 and the XCD 80mm f/1.9 will net the exact same field of view, DoF, etc, if fitted to an X2D or 907x.

That FoV will not be the same as when the Planar 80 lens is fitted to a Hasselblad 500CM and exposing a 6x6 film rectangle in an A12 back because of the different size of the film format (56x56 mm vs the digital sensor's 33x44mm) and a 35FF format sensor is smaller than the CFVII 50c sensor (24x36 mm) leading to different FoVs.

These differences are the basis of all the 'crop factor' confusion of the past 20 years.
 
rdeloe

rdeloe

Well-known member
Godfrey said:
XCD 80... https://www.bhphotovideo.com/c/prod...ad_cp_hb_00000384_01_xcd_80mm_f_1_9_lens.html
Click to expand...
Ha, good job Hasselblad. That's a nice focal length.

Godfrey said:
These differences are the basis of all the 'crop factor' confusion of the past 20 years.
Click to expand...
I just had this conversation about crop factors with 21 students. There was a lot of confusion about "crop factors". My advice to them was to not waste time thinking about crop factors. Just figure out the world looks with the focal lengths on the camera you're using.

I also brought in a selection of film from 35mm through various medium format and up to 4x5 to reinforce how silly it is that 35mm should be viewed as the standard size against which all other sizes are scaled. It all seemed very "old timey" to them. They probably now think I use a rotary phone. ;)
 
Steve Hendrix

Steve Hendrix

Well-known member
rdeloe said:
Ha, good job Hasselblad. That's a nice focal length.



I just had this conversation about crop factors with 21 students. There was a lot of confusion about "crop factors". My advice to them was to not waste time thinking about crop factors. Just figure out the world looks with the focal lengths on the camera you're using.

I also brought in a selection of film from 35mm through various medium format and up to 4x5 to reinforce how silly it is that 35mm should be viewed as the standard size against which all other sizes are scaled. It all seemed very "old timey" to them. They probably now think I use a rotary phone. ;)
Click to expand...

They were like - Wait, you printed out your algorithm?


Steve Hendrix/CI
 
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