Understanding F stops

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Ben
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#1
This might sound like a silly question but I’m deciding between two lenses, one is an f1.4 and one an f2, both 35mm. My question is f1.4 a full stop faster than f1.8 which is the fastest lens I’ve used so far. Just want to get an idea of how much extra light a 1.4 would let In.
 
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Soeren
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#4
When it comes to the opening, not necessarily when it comes to how much more light hits the sensor
 
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Gary
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#5
This might sound like a silly question but I’m deciding between two lenses, one is an f1.4 and one an f2, both 35mm. My question is f1.4 a full stop faster than f1.8 which is the fastest lens I’ve used so far. Just want to get an idea of how much extra light a 1.4 would let In.
f1.4 is only 2/3 stop faster than f1.8. f2 is the next full stop after f1.4.

I guess it depends on what you’re using it for. My use would be for Astro where the extra light would mean I could reduce the exposure time would be an advantage. Others may want it for its very shallow depth of field.
 
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Ben johns
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Ben
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#6
f1.4 is only 2/3 stop faster than f1.8. f2 is the next full stop after f1.4.

I guess it depends on what you’re using it for. My use would be for Astro where the extra light would mean I could reduce the exposure time would be an advantage. Others may want it for its very shallow depth of field.
Right ok. Well I just got a Leica m2 and on a budget for a first lens. So it’s either the 7artisans 35mm f2 or save a little and get the voigtlander 35mm f1.4.
I’d be using the lens a lot inside so that extra stop might be helpful
 
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Simon
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#7
Right ok. Well I just got a Leica m2 and on a budget for a first lens. So it’s either the 7artisans 35mm f2 or save a little and get the voigtlander 35mm f1.4.
I’d be using the lens a lot inside so that extra stop might be helpful
If you're new to rangefinders then I'd suggest holding off the expensive one. Focusing at f1.4 will be a challenge, especially at close distances where parallax is an issue.

disclaimer: I am utterly incompetent with a rangefinder.
 
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Ben johns
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Ben
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#8
If you're new to rangefinders then I'd suggest holding off the expensive one. Focusing at f1.4 will be a challenge, especially at close distances where parallax is an issue.

disclaimer: I am utterly incompetent with a rangefinder.
I’m new ish, I’ve used a Ricoh 500g, I’m new to a good rangefinder, the patch on the 500g is a bit crap, on mine at least.
I was thinking of holding off, the voigtlander is double the price
 
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Richard
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#11
The one thing that always puzzled me was, the smaller the f number=the bigger the hole/opening :confused:
The f number is a fraction of the focal length. So f1.8 on a 50mm lens = 27.77mm opening. f2 = 25mm opening, f4 = 12.5mm opening and so on

Divide focal length by your f number and that's the size of the opening
 
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Alan
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#16
I have one too, use it now and again on my Sony A7. It feels like it could withstand a direct hit from an Exocet.
 
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Alex
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#17
Just want to get an idea of how much extra light a 1.4 would let In.
F stop does not give you that information. T stop does, but lens manufacturers often don't publish it (unless they are cinema lenses), so you will have to look at independent tests.
Lens can often be F1.4 but T1.8 or even worse.

for example Sony's 50/1.4 is actually T1.6 https://www.dxomark.com/sony-carl-zeiss-planar-t-fe-50mm-f-1-4-za-lens-review/

Sigma's 50/1.4 ART is T1.8 https://www.dxomark.com/Lenses/Sigma/Sigma-50mm-F14-DG-HSM-A-Canon-mounted-on-Canon-EOS-5DS-R__1009

on the other hand Sony's 55/1.8 is also T1.8 https://www.dxomark.com/Lenses/Sony...-T-STAR-55mm-F18-mounted-on-Sony-A7R-II__1035
 
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Tony
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#18
Years ago I was wrongly told that it was the area of the the blades not the area of the hole. So a f1.8 is covering less area than f8.

Learn something new every day!!
 

arclight

Oooh that burglar's a cutie
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Doug
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#20
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