Aperture Confusion

[jonrayner]

Something came into my head and I cannot work it out.

Now I may be jumping the gun and this will be dealt with later in the course (I am on lesson 3).

I can set my camera's aperture from F4.5 to F29. My lens goes from F3.5 to F5.6. How does the lens F stops relate/ match to the camera's F stops? The camera has a much larger range than the lens!

Thanks in advance

Jon

[admin]

Something came into my head and I cannot work it out.

Now I may be jumping the gun and this will be dealt with later in the course (I am on lesson 3).

I can set my camera's aperture from F4.5 to F29. My lens goes from F3.5 to F5.6. How does the lens F stops relate/ match to the camera's F stops? The camera has a much larger range than the lens!

Thanks in advance

Jon


Jon, the aperture shown on your lens is a maximum aperture for your lens at wide end (no zoom) and a high end (max zoom). It's not the available aperture range. Both numbers refer to maximums only. Meaning, you can open aperture to f/3.5 at wide angle, but at max. focal length it wouldn't open any more than f/5.6. You can still close it down to f/29 at any focal length no problems.

Prime lenses have just one f-number in their specs. For example f/1.8. It doesn't mean you cannot set the aperture to f/22 or whatever. But it wouldn't open any more than f/1.8.

[jonrayner]

Jon, the aperture shown on your lens is a maximum aperture for your lens at wide end (no zoom) and a high end (max zoom). It's not the available aperture range. Both numbers refer to maximums only. Meaning, you can open aperture to f/3.5 at wide angle, but at max. focal length it wouldn't open any more than f/5.6. You can still close it down to f/29 at any focal length no problems.

Prime lenses have just one f-number in their specs. For example f/1.8. It doesn't mean you cannot set the aperture to f/22 or whatever. But it wouldn't open any more than f/1.8.

Many thanks for the response Admin, so to clarify (so I have it correct in my head), I have a 18-55mm lens:

- focal length 18mm - lens aperture range of f/3.5-f/5.6 - valid camera apertures will be f/3.5-f/5.6. So anything above f/5.6 will be ignored, thus using a camera aperture of f/29 would be the same as using f/5.6.
- focal length 19mm-54mm - aperture range will be that of the camera (F/4.5- F/29)
- focal length 55mm - aperture range of f/3.5-f/5.6 - valid camera apertures will be f/3.5-f/5.6. So anything above f/5.6 will be ignored, thus using a camera aperture of f/29 would be the same as using f/5.6.

Also because my camera does not go down to f/3.5, does that mean that the lens will never use this setting. In my case it will only ever go down to f/4.5?

Apologies if I am being dim, I just can't seem to get this into my head.

Jon

[johnc24]

Hi Jon

I'll try and give my view on it for you.

Ok so the lens you say is 18-55mm.

So when the lens is set to 18mm the maximum opening possible is f3.5
Now if you push the lens to 55mm the maximum opening is only f5.6 at that focal length due to the increase in the distance of the focal length.

It sounds confusing because we are talking maximums and they are smaller numbers.

Basically the info on your lens is telling you :

18-55mm 1:3.5-5.6 which means as above at the minimum focal length of 18mm the lens will manage to open the aperture at 3.5 and thats the widest it will go for that focal length.

but once you increase the focal length eg. 55mm then the lens is can open only to aperture of 5.6 because of the increased focal distance.

No matter what though you should always be able to get to you minimum aperture opening of 29.

Hope that clarifies some things for you.
My explanations aren't great but I hope you get some understanding from it.

Regards
John

[daltoned]

Hi Jon, looking with great interest at your question, I've just stepped up from a fixed lens camera(fuji s9600) and I'm still trying to get to grips with the same question you raised. I keep looking at the properties of shots I've taken to try understand what happening, indeed I was going to post a question as I noticed the data from the fuji macro shots seemed to have a number of different aperture/f stops whereas only one seems to list on the Pentax data. I'm hoping as I get further on in the course things will become clearer and by then I'll be getting more familiar with my camera, the std lens and the Sigma Telelens I've bought. Hope I cope with all thing learning, one thing is certain, it's keeping this retired brain active and that's not at all a bad thing.

[daltoned]

Hi John, your post gives some great info on aperture but I still can't understand your last line
"No matter what though you should always be able to get to you minimum aperture opening of 29."
Would welcome any more detail on this.
EddieD

[jonrayner]

Many Thanks for trying to explain, I am not sure if I am more confused or not, so here is my second attempt at explaining it:

At 18mm max opening of lens = f/3.5
At 55mm max opening of lens = f/5.6
At all focal lengths (18-55mm) I can get an aperture of F/5.6 to F/29. If I am using 18mm I can get a further range by going down to f/3.5 (or f/4.5 because of the camera limitation)

18mm - effective aperture will be f/4.5 as that is the limit of my camera (lens will go to f/3.5, but camera will only go to f/4.5).
55mm - effective aperture will be f/5.6, as that is the limit of my lens (lens will only go to f/5.6, but camera will go to f/4.5)

If that is so, does that mean regardless of any lens I put on my camera I will only ever be able to use the range on my camera. I will never be able to use an aperture bigger than f/4.5?

Also with the max opening being 18mm = f/3.5 & 55mm = f/5.6, does that mean that it is a steady scale between focal length and max aperture, so for example, half way through the focal range at 37mm(ish) is the max aperture f/4.5(ish)?

Many Thanks for your help

Jon

[ladyups]

Many Thanks for trying to explain, I am not sure if I am more confused or not, so here is my second attempt at explaining it:

At 18mm max opening of lens = f/3.5
At 55mm max opening of lens = f/5.6
At all focal lengths (18-55mm) I can get an aperture of F/5.6 to F/29. If I am using 18mm I can get a further range by going down to f/3.5 (or f/4.5 because of the camera limitation)

18mm - effective aperture will be f/4.5 as that is the limit of my camera (lens will go to f/3.5, but camera will only go to f/4.5).
55mm - effective aperture will be f/5.6, as that is the limit of my lens (lens will only go to f/5.6, but camera will go to f/4.5)

If that is so, does that mean regardless of any lens I put on my camera I will only ever be able to use the range on my camera. I will never be able to use an aperture bigger than f/4.5?

Also with the max opening being 18mm = f/3.5 & 55mm = f/5.6, does that mean that it is a steady scale between focal length and max aperture, so for example, half way through the focal range at 37mm(ish) is the max aperture f/4.5(ish)?

Many Thanks for your help

Jon

I hope you don't think I'm butting in, Jon, but I'm confused as to why you think you camera will only open to 4.5? I thought the lens did it all. What kind of camera do you have?
If I'm trying to shoot wide open at 3.5 and I'm doing it in shutter priority, I have to have my shutter speed set to allow the 3.5 aperture...if its too fast, it won't let me use 3.5...the same with shooting at the telephoto end of the lens...55mm. I have to select a shutter speed that will allow my aperture to stop down to 5.6. Maybe I'm confused too..:D To test this, use aperture priority and set the aperture to 3.5, then see what shutter speed it recommends...you can also change the ISO if its too dark for the 3.5.

Mary

[LensBaby]

Hey Jon I found this for you.....this is from this site. I hope this helps.

The actual range of f-stops varies between lenses but the sequence is always the same:



here is where you will find it at -
http://www.great-landscape-photography.com/aperture.html

[johnc24]

18mm - effective aperture will be f/4.5 as that is the limit of my camera (lens will go to f/3.5, but camera will only go to f/4.5).
55mm - effective aperture will be f/5.6, as that is the limit of my lens (lens will only go to f/5.6, but camera will go to f/4.5)

If that is so, does that mean regardless of any lens I put on my camera I will only ever be able to use the range on my camera. I will never be able to use an aperture bigger than f/4.5

Jon


Hi Jon

No you should be able to close the aperture to 3.5 using the 18-55mm lens.(try setting aperture mode and stop down to 3.5 and change focal lengths and if you notice the aperture setting changing after focusing, then this is the minimum the lens can go to at that focal length.after experimenting just whack it up to its maximum aperture setting and see of you notice any difference in shots.)


"If that is so, does that mean regardless of any lens I put on my camera I will only ever be able to use the range on my camera. I will never be able to use an aperture bigger than f/4.5"

To answer the above question if you were to put the 50mm f1.8 prime lens on then you would be able to stop down to 1.8.

The restrictions are on the lens not the camera.

hope all this makes sense.

regards
John

[johnc24]

Hi John, your post gives some great info on aperture but I still can't understand your last line
"No matter what though you should always be able to get to you minimum aperture opening of 29."
Would welcome any more detail on this.
EddieD

Well I mean that the smaller f stops are generally the restriction dependent on the focal length.You should always be able to go to F29 for example or higher depending on the lens.

Its the smaller f numbers that change when focal lengths are increased. (I mean the larger f numbers can change also but its not that important.)

hope this makes sense.

Regards
John

[jerryph]

Let me see if I can explain a little.

Your lens is an 18-55 and an aperture of 3.5 to 5.6, so lets look at this FIRST.

It means that at a wide angle of 18mm, your MINIMUM aperture will be 3.5 and that as you zoom up to 55mm, your MINIMUM aperture will be 5.6... so though you can touch F/3.5 at 18mm, you cannot at 55mm.

However, you *CAN* go smaller (numerically bigger) apertures than the minimums... up to our MAXIMUM of F/29 (I believe you said).

Your aperture controls your depth of field... or in simpler terms, how deep you can see into your picture and still remained focused.

Let me use examples from my assignment submissions to demonstrate:


My camera/lens combination has different capabilities than yours, but you should be able to recreate the basic effects/results:

Look at the first picture below... note that both "characters" are in focus. My DOF or depth of field is deep at a setting of F/11 (you may not need to go all the way up to F/29... but you COULD if you wanted to):

http://farm3.static.flickr.com/2379/2230616818_813c6220fc.jpg

Look at the second picture. Note that now, only ONE of the characters are in focus. My depth of field is very narrow at a setting of F/1.4 (for your lens, the smallest you could go is F/3.5 if you were at 18mm on your lens or F/5.6 if you had it zoomer to 55mm):

http://farm3.static.flickr.com/2089/2229823445_bb83fde52f.jpg

The smaller the F-stop numerical value, the shallower the depth of field.

This effect of blurring the background has a name, its called BOKEH. The amount of bokeh is controlled by 3 factors:

- The distance from your camera to the front subject
- The distance from the subject to areas behind it
- Your F-stop setting. The numerically higher the aperture, the LESS blurred things in the background become.

To blur the background, the aperture has to have a lower numerical value AND the distance from your camera to your front subject has to be LESS than the distance from your FRONT subject to your REAR subject. The further the rear subject is, without changing ANY setting on your camera or lens... the more bokeh (blurry), you get.

I hope that helps.

[johnc24]

sweet reply jerry

you put a lot into that one...well done!

regards
John

[ladyups]

Excellent explanation! Thank you, Jerry..

Mary

[dkippen]

Yeah - I think I get it now too.

[Snappers]

I need to read this again when I get home and my connection is not playing up as the pictures are not showing for me.

[jonrayner]

Many Thanks for the explanations everyone. I believe I now FULLY understand it. It has not helped because I was not looking at the camera correctly; although I understood that the max aperture was different at each end of the zoom, I did not think that the camera settings changed when the focal length changed, i.e I looked at the aperture settings on the camera at only one focal length which at the time the available aperture settings were f/4.5 - f/29. So here it goes!!!

At focal length 18mm I can amend the aperture from f/3.5 to f/22
At focal length 55mm I can amend the aperture from f/5.6 to f/36

then at a couple of random focal lengths in between the min and max ranges:

At focal length 35mm I can amend the aperture from f/4.5 to f/29
At focal length 25mm I can amend the aperture from f/4.0 to f/29

It seems so simple now, feel I little bit dumb, but hey don't mind too much as I now understand it (unless someone contradicts what I have just said, please don't, not sure I'll cope!)

Jerryph - Thanks for the information about DOF, although I think I understood it, this definitley confirms it. Great example pictures, thank you for the effort you went to.

[johnc24]

"It seems so simple now, feel I little bit dumb, but hey don't mind too much as I now understand it (unless someone contradicts what I have just said, please don't, not sure I'll cope!"


NO jon you have it all wrong, all wrong I tell you!! LOL

only kidding im sure you would have coped anyway

glad you have it now.

regards
John

[dkippen]

Jon and John

(Hey, I hope this isn't like Dumb and Dumber?? Nah - we're all smarter than that)

Anyway, this helps me a lot as well since I have the same camera as Jon. I think I'll print out some of these posts for reference.

[daltoned]

After reading Jerry's detailed explanation of the aperture stops, I had another look at my camera and as John said " feel a little dumb". Thanks guys for this thread and the responses.It's made me look beyond Auto settings where the camera does the work and I can now look forward to the course lessons on aperture.

[sanzia]

I can fully relate to this confusion. In the lesson 4, I could NOT get my A Priority F Stop to go below 5.6, but it did go way up to F.32, and this was with the lens [200mm Nikon] zoomed out all the way, yet there are times this lens goes down to 4.5. I am wondering if available light had anything to do with it, as we have had so many gloomy days. Now I have taken my pics, the sun comes out.

I now understand A Mode, and will probably end up adopting it as my favorite, but I think there is a lot more to this Aperture than we realize.

Sanzi

[jerryph]

Ok, let's simplify...

You have a lens that is called an 18-55. The apertures are 3.5 to 5.6

Do you understand that the small numbers are BIG aperture openings and big numbers are SMALL aperture openings?

The numbers just mean that at the 18mm end of your lens, the biggest aperture you can get is 3.5 and that when you zoom to 55mm, the biggest aperture you can get is 5.6.

An easy way to see this happening is to put your camera in aperture priority mode and set it to the biggest (numerically smallest) number possible. Now zoom slowly in and out and watch the aperture settings on your camera change.

Now, if you set your aperture manually to F/8 and zoom in and out, nothing changes, but if your aperture at 18mm is F/3.5, as you zoom up from 18mm to 55mm, it rises from F/3.5 to F/5.6 and this is becuase the maximum openings of your lens gets smaller as you zoom forward. It can do all apertures from F/5.6 to F/29 between 18-55 but underneath that, your lens has restrictions, thats all that means.


This is not what happens on a more expensive lens that has a fixed aperture of (let's say) F/2.8.

[LensBaby]

Jerry...Do you know it only took me several years to figure this out? I was so confused by those numbers on there, and not one book I have read yet, as explained it as well as you did. Many thanks!

[LensBaby]

Wow I have been playing around with my camera all day, and this aperture thing has really came in handy. Thanks again Jerry!

[jerryph]

Don't you love it when the lightbulb flicks on? I remember how happy I was when I tripped across it myself. :D

[jerryph]

I now understand A Mode, and will probably end up adopting it as my favorite, but I think there is a lot more to this Aperture than we realize.


Actually, there really isn't that much more at all. A-mode is a tool, and I personally still have no issues using the best tool for the job, but for me, nothing gives me better more complete control than manual (and no I am not talking about mexican names... lol)

[LensBaby]

LOL too funny! Yeah for some reason I love manual. I need to learn it better, but hey everybody has to start somewhere. Over the summer I will have more free time, because the kids will be on vacation.