f stop range

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Daniel Alexander

Active member
ok so all the advice points towards getting the fastest lenses as possible, f1.2 etc however for the less financially secure (ahem) I would like to know the limitations of getting lenses in the 2.8 range instead, does it just mean i will have to compensate my lights for an extra stop or two? I ask because I am about to buy a Letus elite and want to get a 50mm, 28mm and 135mm and really want to know if its just a couple stops of light il be losing or do the actual optics suffer/have less quality etc? Thanks

PS im thinking about getting Nikon primes on an EX1 but my main concern is getting the best bang for buck (or pound in my case), so also if anyone has any pointers towards cheaper alternative lenses that are still optically stunning please chime in.

Thanks guys
 
the difference between f/1.4 and f/2.8 on an adapter is not 2 stops as it would be on a DLSR or film camera.... it's more along the lines of 1/2 a stop. the difference between f/1.4 and f/2 is about 1/10th of a stop...

optically most lenses are fine - it's the mechanics you've got to watch out for! slow wide lenses tend to vignette on adapters.

if you go with nikon lenses my budget kit recommendations would be;

28mm f/2 AI
35mm f/2 AI
50mm f/1.4 AI
85mm f/2 AI
135mm f/2.8 AI
52mm rotating polarizing filter (fits all the lenses)
extension tube set


i recommend buying a nikon 50mm f/1.4 AI. test it out then decide what else you want after mucking around with different focal lengths in a photography shop.
 
Shooter said:
Just curious. How did you work this out?
Click to expand...

the difference varies from adapter to adapter depending on the diffusion of the GG. that was just a guesstimate of what my old letus used to be. i have properly measured my sgpro with a wavelength monitor in a similar way to dennis wood did in his tests.
 
Shooter said:
Just curious. How did you work this out?
Click to expand...

I believe it's been demonstrated that due to the different diffusion level on each adapter's GG, light loss is no longer linear. So stopping down one stop doesn't necessarily mean losing twice the amount of light. This is different for each adapter brand.
 
So you both are saying that the f-stops on a lens (mounted to an Adapter) are no longer working as "physics" would tell us they should.

Fascinating... I will do a test later this week to satisfy my incredulity.

(I wll use a waveform monitor, light meter and a grey scale card under lit conditions)
 
I once read about about this non-linear relationship. Interesting phenomenon - I must admit I can hardly believe it - will have to test myself ;)
If the difference between 1.4 and 2.0 is, in fact, 1/10th of a stop, why it's not the case when you compare, say, 4.0 and 5.6? How can the gg be aware of the absolute value of the aperture hole?
 
I dont think the non linear relationship with the adapter is quite the same as saying there is a difference in the factors between the f-stops of a lens when a given lens is mounted on a DOF Adapter.

Tests will tell all maybe.

A comment on "ok so all the advice points towards getting the fastest lenses as possible"

I suspect this has come from the "Indie" world where a lighting kit /rig is less likely to be on hand due to the nature of the genre. Shooting without lighting probably means that getting any bit of free light available is important (with its down sides as well as its upsides.).

A VERY fast lens is not an actual pre requisite of using an adapter though and other "slower" lenses should not be disregarded for that reason alone.
 
i did lots of tests last year. a good one is to set up your adapter (without a camera) facing a grey card/evenly lit wall. then point a spot meter through it and see what it says :)
 
jenningsp said:
i did lots of tests last year. a good one is to set up your adapter (without a camera) facing a grey card/evenly lit wall. then point a spot meter through it and see what it says :)
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Clever. What did you conclude from the test?

Would then be interesting to do the same test pointing a spotmeter thru the eye piece of a SLR camera with same lens at the same subject.
 
Shooter said:
A comment on "ok so all the advice points towards getting the fastest lenses as possible"

I suspect this has come from the "Indie" world where a lighting kit /rig is less likely to be on hand due to the nature of the genre. Shooting without lighting probably means that getting any bit of free light available is important (with its down sides as well as its upsides.).
Click to expand...

It's moslty about vignetting like jennings said earlier. Slower lenses tend to vignette more when used with adapters, especially slower wide angle lenses.
And when I say slow, i should really be saying, "not fast enough" because f/2.0 is even too slow for some wides. I don't know why, some people specualte it has somehting to do with the size of the rear glass element. The faster the lense the larger the rear element. The larger the rear element, the less vignetting.
 
jenningsp said:
that i wasted money on f/1.4 lenses... :) f/2 lenses are perfectly fine in terms of speed. it just reconfirmed what i saw on the wavelength monitor.
Click to expand...
Although I don't doubt the results of the test you did, you may want to let us know the light levels you conducted the test.

4Ex: if the light was "plenty" for any aperture (to run the test), then I agree it did not make any difference and 2 was fine (no need for a 1.4 because you can close down the iris of the camcorder).

But if the light was "just enough" for a 1.4 lens...... than a "2" (max aperture) could not simply provide enough light. In many cases, "that" is the difference between a "got it" a "dam' it, we need some lights" scene (in ambient light, dark alleys at night, natural interior lights, moody atmosphere, etc).

Why would primes be so expensive if not that valuable?

I got (just like everybody else) an 18-55 (and 50-200) with 4/5.6 aperture on my digital. I would trade both zooms for two primes (35/1.4 & 85/1.4). Today.
(I wouldn't have to shoot at 800 ISO to get some pictures).
But then again, that may be just me 2c.
 
dan, if your in a lot of circumstances where 1/10th of a stop is the difference between getting the shot and not, then i would recommend getting f1.4 lenses.

here are a couple of reference shots. they were shot with a standard gamma and a slightly crushed master ped. so the differences in exposure would be less obvious with a cine gamma.

and keep in mind the sgpro uses a more diffused GG than the letus elite (which is what we're talking about in the thread right?) so the difference between f1.4 and f2 would be even less with the letus!!!

dvxf2_8_sgprof1_4.jpg

dvxf2_8_sgprof2.jpg



if you flick between those two you can see the difference. but if you look at one and then the other you'd be hard pressed.

this is what stopping down one stop is supposed to look like -
dvxf4_sgprof1_4.jpg
 
jenningsp said:
dan, if your in a lot of circumstances where 1/10th of a stop is the difference between getting the shot and not, then i would recommend getting f1.4 lenses.
Click to expand...

Thanks for your recommendation Patrick, I did so some five years ago. Nikon 35/1.4, 55/1.2 and many others...
(the primes I wished for was for my SD10, btw)

I got (back then) when using those primes (with an adapter) the same results as you posted today, so.. I guess we just endorsed somehow each other's findings.:beer:
 
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