What does F stop have to do with lense speed

This 2 lenses are my Canon EF 50mm lens.
The one on the left is f/1.4 version and the one on the right is the f/1.8 mk1 version
Both lens were set at f/4 and their aperture size is about the same (of course, different shape since the f/1.8 version has less blades)
Since aperture is the ratio of focal length to effective aperture diameter and both lens are 50mm (focal length) with aperture set at f/4, therefore the physical aperture size should be the same. And it has nothing to do with filter size.




4753893396_a6a6a94a55_b.jpg

How did you set them both at f/4 with them off the camera?

This is probably a stupid question....but I must ask it lol in the pursuit of knowledge. :mrgreen:


im not too sure about canon. but i know on the nikon 50mm 1.8 and 1.4 they have an aperture ring so you could adjust the aperture on the lens itself.
 
This 2 lenses are my Canon EF 50mm lens.
The one on the left is f/1.4 version and the one on the right is the f/1.8 mk1 version
Both lens were set at f/4 and their aperture size is about the same (of course, different shape since the f/1.8 version has less blades)
Since aperture is the ratio of focal length to effective aperture diameter and both lens are 50mm (focal length) with aperture set at f/4, therefore the physical aperture size should be the same. And it has nothing to do with filter size.




4753893396_a6a6a94a55_b.jpg

How did you set them both at f/4 with them off the camera?

This is probably a stupid question....but I must ask it lol in the pursuit of knowledge. :mrgreen:


im not too sure about canon. but i know on the nikon 50mm 1.8 and 1.4 they have an aperture ring so you could adjust the aperture on the lens itself.

Ahh ok.

None of my 8 lenses have this.
 
Neil, I learned that from the net in the past since Canon AF lens do not have the aperture ring.

- Mount the lens
- Set the aperture from the dial on the camera
- Press and hold the "Depth of field preview" button (like you said in your post)
- Gently remove the lens from the camera while holding both Depth of field and Lens release buttons.

That's it! Hope this help. :)

Of course .... Do this at your own risk LOL I am not responsible for any damage that may cause ... although it works for me and no harm to my cameras and lenses.
 
The reason I questioned all this is because I have been buying lenses and have been playing with aperature and depth of field for some time. What I was hoping to do was increase depth of field and increase shutter speed I thought I could do this with a wider filter size. Sounds like I need to learn more about the inside of the lense. When I go to someone who sells lenses and ask about them they don't seem to be able to tell me much they just want to tell me what i have to buy. For me to be better educated about what I am getting will help choose my lenses in the long run. So far from since I have purchased my lenses I have noticed the lenses shorter and closer to the camera catch things much better than longer zoom lenses. With the short I get sharp fast images at fast shutter speeds, With longer lenses I get motion blurr alot since I don't have VR. My main goal is to get lenses with increased depth of field and get plenty of light to have a faster shutter speed. Right now I have a D40 and hope to be ready when I get my D90. I do everything manual and have been since I first got the camera.
 
The reason I questioned all this is because I have been buying lenses and have been playing with aperature and depth of field for some time. What I was hoping to do was increase depth of field and increase shutter speed I thought I could do this with a wider filter size.
Filter size is a different discussion.

With longer lenses I get motion blurr alot since I don't have VR.
Not to be funny, but it's likely down to improper/inadequate shooting technique.... i.e. operator error. I would look in the mirror (literally) to see what your method is and how to stabilize your gear better.
 
If you get motion blur its not from not having VR - VR only counters motions made by your hands/body and the support of the camera it has no effect on blur caused by a moving subject - that is the domain of the shutter speed alone.

Typically the slowest most people can hand hold is 1/focal length of the lens - so for a 50mm lens 1/50sec for a 300mm lens 1/300sec in order to counter shake from your hands holding the setup. If you use a tripod, monopod or other support you can remove this effect (and for many lenses its advisable to turn off IS/VR when mounting to a tripod otherwise the antishake makes its own shake when there is none to counter).

If you want faster shutter speeds you really have three options:

1) Use a higher ISO - of course the penalty for this is increased noise levels in your shots. Good exposures and editing as well as a good camera body can of course greatly extend the range of ISOs that you are able to use - also the amount you can use before photos are "too bad" is based upon you're own output of the photos as well as your own standards

2) Increase the aperture (use a smaller f number) -taking the penalty of a smaller depth of field of course as a result. Also many lenses might not be their sharpest when shot wide open (at the largest aperture/smallest f number).

3) Increase the light upon the subject - either waiting for more lighting to appear (eg a different time of day/weather) or adding your own in the form of reflectors, flashes and strobes (constant light sources). Of course this is again not always possible to use as it might have its own restrictions.


A wider filter size does not always mean that you have larger front glass, the filter is a measure of the thread size and some lenses can have a deep ring around the lens before the filter is mounted. Also as said above the front element/glass size is not the only thing that determins the amount of light you have to work with because of the inner workings of the lens and the aperture setup.



As for what you are after - more depth of field with more light - as far as I know there is no lens that will give you that effect. If you want more depth you have to close down the aperture and thus that means less light for you to work with - meaning that you have to draw upon the other key areas of the setup outlined above. Don't let this discourage you from wide aperture lenses though as many of these are of a higher grade of lens - meaning that features (AF, VR, build quality) are improved and that the overall optical performance is generally superior to lesser lenses in the same range.
 
I keep hearing about lenses being fast because of being an f 1.2 or 1.4. I have purchased a 2.8 and a 1.8 and to me 1.2 and 1.4 make no sense to me.
When I see pictures taken at those numbers the part at the lense is clear then the rest goes out of focus without. To me you should have some transition. Example: A picture of a cat I saw taken at 1.8 had a clear face and the cat was sitting pretty. The body and the background are just as blurry as can be. I would rather see a transition or at least the face and body in focus and the background out of focus. I have to crank down to f3 for starters and f11 on the other end and rarely 1.8 unless I am at infinity. I keep being told I should have went with the 1.4 that is way more expensive so I would be pay way more for a lense I would crank down anyway. 1.4 is only faster if you use 1.4. I almost never would.

What I have figured is that if you have to crank down the f stop anyway then would a wider filter size be a faster lense since the wider lense lets in more light and allowing you to make shutter speeds faster. If you can crank the shutter speed faster with a lower f stop and wider lense then why does f stop have anything to do with speed? The wider the f stop the less is in focus. Wider lense makes more sense to me as far a speed goes. Am I not understandin somthing about this? Because at this point lower f stops than f 2 seem like money in the garbage to me. Help me out on this one.

F-stops are fractions, therefore the smaller the number, the larger the value is. 1/2 is more than 1/16. When writing, use this notation: f/16. That makes it clearer that it is a fraction. The 'f' in 'f/16' represents the focal length of the lens (28mm, 50mm, 300mm etc.) Thus the absolute aperture of the setting 'f/4' on a 30mm lens is 300/4 or 75mm. When you have a 300mm f/4 lens wide open, the opening in 75mm across. At f/8, it's 300/8 or 37.5mm. On the other hand, a 100mm lens set to f/4 will have a clear opening of the diaphragm of 25mm (100/4). This is why we use f-stops, so that all lenses can be easily controlled using the same numbers. The 300mm lens at f/4 and the 100mm lens at f/4 transmit the same amount of light, even though the 300mm lens has an opening of 75mm and the 100 has an opening of 25mm. (Though in some cases the actual amount of light the two lenses transmit may vary slightly due to absorption by large numbers of elements; this can generally be ignored.) That's why the true term is 'relative aperture'.

The 'speed' of a lens refers to its maximum aperture (lowest f-number). An f/2 lens is 'faster' than an f/4 lens, because 1/2 is more than 1/4. A half dollar is worth more than a quarter dollar.

WalkingLibertyHalfDollar1944-SNG-5.jpg




1923_s_standing_liberty_quarter_obverse.jpg
 
If you get motion blur its not from not having VR...

Based on semantics, maybe you are right (depending on definition of motion blur), but shooting @ 300mm w/o VR will definitely be less sharp...which really just means it is slightly blurred.

I completely agree that VR will do nothing to stop a moving subject.
 
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If you get motion blur its not from not having VR...

I guess if you want to argue semantics, maybe you are right (depending on definition of motion blur), but shooting @ 300mm w/o VR will definitely be less sharp...which really just means it is slightly blurred.

I completely agree that VR will do nothing to stop a moving subject.

I use long lenses lacking image stabilization (180mm, 350mm, 560mm) all the time. Good technique is all that it takes. I rarely have camera shake, but having a heavy camera and lens combo helps: the mass resists movement.
 
What I meant when I said motion blurr was my wiggly hands. I would love to be able to take out a camera in the field and get better shots. It is hard lugging tripods and lights out in the field. Big thing I need is to take lenses out in the field and have as much versatility and speed as possible. One other thing that is hurting me now is not having auto focus. I did not realize that when buying a D40 I would not have it. I have no doubt that my wiggly hands are not helping.
 
@ 300mm w/o VR will definitely be less sharp...which really just means it is slightly blurred.

300mm f/4 mounted on a D300, handheld.


BeesinRedbud-2.jpg



It might have some slight blur issues, but I can live with them.​
 
What I meant when I said motion blurr was my wiggly hands. I would love to be able to take out a camera in the field and get better shots. It is hard lugging tripods and lights out in the field. Big thing I need is to take lenses out in the field and have as much versatility and speed as possible. One other thing that is hurting me now is not having auto focus. I did not realize that when buying a D40 I would not have it. I have no doubt that my wiggly hands are not helping.

You don't need autofocus. You don't need VR either. Both cause some limitations on lens quality. I use Leica stuff, the best line of lenses overall on the planet, and I assure you that you want to develop good technique.

I hate tripods and use one only as a last resort.
 
Monopods can be a good stablity aid for longer, heavier lenses without adding much weight or bulk to a setup.
 
If you get motion blur its not from not having VR - VR only counters motions made by your hands/body and the support of the camera it has no effect on blur caused by a moving subject - that is the domain of the shutter speed alone.

Typically the slowest most people can hand hold is 1/focal length of the lens - so for a 50mm lens 1/50sec for a 300mm lens 1/300sec in order to counter shake from your hands holding the setup. If you use a tripod, monopod or other support you can remove this effect (and for many lenses its advisable to turn off IS/VR when mounting to a tripod otherwise the antishake makes its own shake when there is none to counter).

If you want faster shutter speeds you really have three options:

1) Use a higher ISO - of course the penalty for this is increased noise levels in your shots. Good exposures and editing as well as a good camera body can of course greatly extend the range of ISOs that you are able to use - also the amount you can use before photos are "too bad" is based upon you're own output of the photos as well as your own standards

2) Increase the aperture (use a smaller f number) -taking the penalty of a smaller depth of field of course as a result. Also many lenses might not be their sharpest when shot wide open (at the largest aperture/smallest f number).

3) Increase the light upon the subject - either waiting for more lighting to appear (eg a different time of day/weather) or adding your own in the form of reflectors, flashes and strobes (constant light sources). Of course this is again not always possible to use as it might have its own restrictions.


A wider filter size does not always mean that you have larger front glass, the filter is a measure of the thread size and some lenses can have a deep ring around the lens before the filter is mounted. Also as said above the front element/glass size is not the only thing that determins the amount of light you have to work with because of the inner workings of the lens and the aperture setup.



As for what you are after - more depth of field with more light - as far as I know there is no lens that will give you that effect. If you want more depth you have to close down the aperture and thus that means less light for you to work with - meaning that you have to draw upon the other key areas of the setup outlined above. Don't let this discourage you from wide aperture lenses though as many of these are of a higher grade of lens - meaning that features (AF, VR, build quality) are improved and that the overall optical performance is generally superior to lesser lenses in the same range.

Much of what you said were points that I was trying to stay away from. Like raising ISO and increasing depth of field. No doubt using a bigger lense is challenging to me and I probably do need to work better on techniques with that. Small lenses are easy for me normaly.

For me this post is a reality shock. My assumptions and guesses have been proven wrong and this now changes the direction of my understanding. Refining technique after this post seems more like the problem I am having and not getting better lenses. I have been working with reptiles and flowers with macro for somtime now and that is easy. Catching things at a distance and doing more with people is somthing I would like to do next and there have been some challenges there. It sounds like many times if I don't create the perfect shot I just won't get it and I need to learn to work with what I have. Taking the information given to me in this post and making notes tells me where I need to start learning and practicing and I feel there will be some challenges here but hope I get over them and start getting some awsome shots. This post has been overwhelming with information but truly educational for me.
 

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