
This should be a sticky.
Thanks Ecking  I've been curious about purchasing a 2nd speedbooster & I own a pocket and 2.5. I own the regular m43 speed booster so this is really helpful to know that to match them pretty closely would be a matter of purchasing the bmpcc specific one!
Can you all help me understand these numbers because they don't add up to me. I read in different places the original crop of the bmpcc is 3.02x and then other places say 2.88x . So I may be doing the math wrong but if I take 3.02x * .58 = 1.75x effective crop or 2.88x * .58 = 1.67x (which is APSC I think). Now with that being said if I take the Sigma 1835mm f/1.8 * 1.75x = 3161mm f/1.0 true or false?
If true how can Metabones claim the 1835mm becomes a 1020mm f/1.0? It seems they are applying the .58 reduction to the focal length is this the correct way to gauge the applied focal length with the adapter. I also notice Andrew from EOSHD said the first version of the metabones speed booster gave a 2.1x crop and made the Sigma 1835mm a 3875mm f/1.2. However according to Metabones and their math, with the original SB then the Sigma should be a 1224mm f/1.2.
So which way is the correct way ?
Edit: I might have answered my own question but still would like some insight. So I applied the .58 reduction to the focal length of the Sigma and got 1020mm, multiply that by the original 3.02x crop of the pocket and we get the 3161mm f/1.0 or 2.88x is 2857mm f/1.0. So technically its does make the Sigma a 1020mm f/1.0 but its rather misleading as its not actually that wide on the pocket(could be wrong I dont own either yet). I just like to research and know these things before hand.
Last edited by Abstrak; 04042014 at 08:59 PM.
Crop factors are a curse, and only seem to lead to needless confusion. When comparing the BMPCC to 35mm still format you have the complexity of comparing two different aspect ratios in addition to two different format sizes. The BMPCC has an aspect ratio of 16:9, while 36x24 format has an aspect ratio of 3:2 (or 13.5:9). So if you compare diagonals the crop factor of the BMPCC is 43.27/14.319 = 3.02. On the other hand, if you compare the horizontal dimension you get 36/12.48 = 2.88.
The 0.58x Speed Booster reduces the focal length and fnumber of a lens by a factor of 0.58x. Pure and simple. The 0.58x S.B. plus the 1835/1.8 Sigma really does become a 10.420.3mm f/1.0 lens, and there's nothing misleading about it once you get used to how focal lengths translate to field of view on the BMPCC format. Note that a 10.420.3mm f/1.0 lens is *very* different from a 2058.5mm f/1.0 lens because the latter would have a much larger entrance pupil diameter and correspondingly shallower depth of field.
Well wiki is crowd sourced just like our input. I am not aware of an APSC sensor that is wider than film S35 as this Wiki entry apparently claims. The APSC Nikon sensor is wider than the APSC Canon sensor such as the 7D but it's still smaller than film S35 I believe.
Thanks for the explanation Brian!
Guys can some one point me in the right direction on how to figure out what my lens becomes after adding it to a particular speed booster. I am trying to figure out what my BMCC + bmcc SB with 58mm and 2x Anamorphic becomes? thanks
It's also handy to have the diagonal length which will tell you what your normal lens is for that sensor. Maybe not directly translatable to film but the photographic rule of thumb for range is: half the normal focal length for landscape, 2x for portrait, 4x for sports and 8x for wildlife.
I have this bookmarked and come back here for reference a lot. So I wanted to add one more comparison. There is another speed booster type adapter available that is like a wireless follow focus device called DEC Aperture LensRegain. The reduction is just .75 so won't get as much improvement as the Metabones but the addition of wireless follow focus is something to think about. Not to mention that on the BmCc with the passive MFT, this adapter lets you use all the canon lenses and IS you want since it controls the iris, focus and power to the lens.
BMCC = 15.81mm x 8.88mm
BMCC + DEC LensRegain (.75) adapter = 21.08mm x 11.84mm
BMCC + MFT (.71) Speedbooster = 22.27mm x 12.51mm
BMCC + 'BMCC' (.64) Speedbooster = 24.7mm x 13.88mm
BMPCC = 12.48mm x 7.02mm
BMPCC + DEC LensRegain (.75) adapter = 16.64mm x 9.36mm
BMPCC + MFT (.71) Speedbooster = 17.58mm x 9.89mm
BMPCC + 'BMCC' (.64) Speedbooster = 19.5mm x 10.97mm
BMPCC + 'BMPCC' (.58) Speedbooster = 21.52mm x 12.1mm
Blackmagic Production Camera = 21.12mm x 11.88mm
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