question about f-stops

[Ika]

Originally posted by: AMDUALY

Originally posted by: Aflac
if you don't get it before I get home, I'll take out my S3 and try a few things. The S3 isn't the best camera to make example pics, but it should work...

SLRs are the only ones that can create this affect to a degree where it is very noticeable.

Possibly, but the S3 is a rather capable camera. It won't be as effective as an SLR, but it still should be able to show the effect.

 

[fuzzybabybunny]

Originally posted by: pontifex

Originally posted by: Quasmo
Also, try moving your self back, and zooming in all the way. A lower f-stop means more light comes in, so you want alot of light to get a a higher f-stop, and then close the iris.

maybe i should use a differnt lens? like a 70-300 or a 28-80?

the thing is, when i zoom in, the fstop changes to a higher number too.

The f-stop changes because there are different maximum apertures at different focal lengths. Your Nikkor 18 - 55mm is f/3.5 - 5.6, meaning at 18mm f/3.5 is the max aperture, and at 55mm f/5.6 is the max aperture. If you've got the lens set at f/4 at 18mm and zoom to 55mm, the aperture will automatically change to f/5.6 because it can no longer physically maintain an aperture of f/4.

 

[40Hands]

Originally posted by: Aflac

Originally posted by: Quasmo

Originally posted by: pontifex

Originally posted by: Quasmo
Also, try moving your self back, and zooming in all the way. A lower f-stop means more light comes in, so you want alot of light to get a a higher f-stop, and then close the iris.

maybe i should use a differnt lens? like a 70-300 or a 28-80?

the thing is, when i zoom in, the fstop changes to a higher number too.

that shouldn't happen.

Sure about that? My camera changes from a maximum aperture of f-2.7 at the widest setting, but it changes to f-3.5 at the maximum zoom setting (432mm, 35mm equivalent).

It should change. With a lens that does not have a constant aperture, it has to change when you zoom in or out.

edit: beat by the photo bunny.

 

[DeviousTrap]

Originally posted by: Quasmo

Originally posted by: pontifex

Originally posted by: Quasmo
Also, try moving your self back, and zooming in all the way. A lower f-stop means more light comes in, so you want alot of light to get a a higher f-stop, and then close the iris.

maybe i should use a differnt lens? like a 70-300 or a 28-80?

the thing is, when i zoom in, the fstop changes to a higher number too.

that shouldn't happen.

Yes it should. Unless you have an expensive lens with a fixed aperture throughout the zoom range, the min. f-stop will increase as the zoom level increases.

 

[Quasmo]

Originally posted by: fuzzybabybunny

Originally posted by: pontifex

Originally posted by: Quasmo
Also, try moving your self back, and zooming in all the way. A lower f-stop means more light comes in, so you want alot of light to get a a higher f-stop, and then close the iris.

maybe i should use a differnt lens? like a 70-300 or a 28-80?

the thing is, when i zoom in, the fstop changes to a higher number too.

The f-stop changes because there are different maximum apertures at different focal lengths. Your Nikkor 18 - 55mm is f/3.5 - 5.6, meaning at 18mm f/3.5 is the max aperture, and at 55mm f/5.6 is the max aperture. If you've got the lens set at f/4 at 18mm and zoom to 55mm, the aperture will automatically change to f/5.6 because it can no longer physically maintain an aperture of f/4.

I'm a videographer applying my techniques to photography, haven't run into that with the lenses I use...

Damn, I got pounded for not know about cheap lenses

 

[fuzzybabybunny]

Originally posted by: Quasmo

Originally posted by: fuzzybabybunny

Originally posted by: pontifex

Originally posted by: Quasmo
Also, try moving your self back, and zooming in all the way. A lower f-stop means more light comes in, so you want alot of light to get a a higher f-stop, and then close the iris.

maybe i should use a differnt lens? like a 70-300 or a 28-80?

the thing is, when i zoom in, the fstop changes to a higher number too.

The f-stop changes because there are different maximum apertures at different focal lengths. Your Nikkor 18 - 55mm is f/3.5 - 5.6, meaning at 18mm f/3.5 is the max aperture, and at 55mm f/5.6 is the max aperture. If you've got the lens set at f/4 at 18mm and zoom to 55mm, the aperture will automatically change to f/5.6 because it can no longer physically maintain an aperture of f/4.

I'm a videographer applying my techniques to photography, haven't run into that with the lenses I use...

Video lenses confuse me.

 

[Zenmervolt]

Originally posted by: pontifex
i think this lens only goes to f4 or maybe f3.5

Too slow for the shallow depth of field you're looking for. You'll want a maximum of F2.8. Honestly, for learning about it, find an inexpensive 50mm prime that will open up to F1.4 and then you can play with it and see what sort of F-stop you need for the effect you want. It's all trial and error because only you know the effect you want.

ZV

 

[tfinch2]

There are two factors that affect DoF. Aperture and subject distance. For example, both of these images were shot at f/8

http://i.pbase.com/o4/08/648408/1/58826835.dinner.jpg
http://i.pbase.com/o4/08/648408/1/63791428.HGgFO8h5.nina.jpg

Use you camera in A mode to control the aperture and experiment.

Also, DoF on a kit lens is going to be less noticeable unless you are close to the subject, or the subject and objects around it are very far apart depth-wise.

 

[Zenmervolt]

Originally posted by: AMDUALY

Originally posted by: Aflac
if you don't get it before I get home, I'll take out my S3 and try a few things. The S3 isn't the best camera to make example pics, but it should work...

SLRs are the only ones that can create this affect to a degree where it is very noticeable.

Wrong. I can set my Olympus C-8080 at F2.4 and it'll create a nice bokeh behind the subject.

As long as you have manual control over the aperture offered, you can get the effect.

ZV

 

[Zenmervolt]

Originally posted by: Quasmo

Originally posted by: pontifex

Originally posted by: Quasmo
Also, try moving your self back, and zooming in all the way. A lower f-stop means more light comes in, so you want alot of light to get a a higher f-stop, and then close the iris.

maybe i should use a differnt lens? like a 70-300 or a 28-80?

the thing is, when i zoom in, the fstop changes to a higher number too.

that shouldn't happen.

Yes, yes it should. Unless he spent a couple thousand dollars on the lens. Almost any zoom that is affordable for a consumer has a variable F-Stop (remember that F-stop is a ratio involving focal length) and the maximum aperture is only attained at the widest setting. Most consumer zooms are in the F3.5-5.6 range, meaning that at wide angle they are F3.5 fully open and at full zoom they are F5.6 fully open.

ZV

 

[Feldenak]

Originally posted by: BroeBo
Here is one of mine at 75mm f/4

http://www.pbase.com/broe/image/59584761/




Ah I see the D50 does not have the DOF preview button like the XT and D70

That's one thing I wish the D50 did have.

 

[tfinch2]

Originally posted by: Zenmervolt

Originally posted by: AMDUALY

Originally posted by: Aflac
if you don't get it before I get home, I'll take out my S3 and try a few things. The S3 isn't the best camera to make example pics, but it should work...

SLRs are the only ones that can create this affect to a degree where it is very noticeable.

Wrong. I can set my Olympus C-8080 at F2.4 and it'll create a nice bokeh behind the subject.

As long as you have manual control over the aperture offered, you can get the effect.

ZV

Sensor-size plays a big part in visible DoF in digital images.

 

[Quasmo]

Originally posted by: tfinch2

Originally posted by: Zenmervolt

Originally posted by: AMDUALY

Originally posted by: Aflac
if you don't get it before I get home, I'll take out my S3 and try a few things. The S3 isn't the best camera to make example pics, but it should work...

SLRs are the only ones that can create this affect to a degree where it is very noticeable.

Wrong. I can set my Olympus C-8080 at F2.4 and it'll create a nice bokeh behind the subject.

As long as you have manual control over the aperture offered, you can get the effect.

ZV

Sensor-size plays a big part in visible DoF in digital images.

A HUGE Part, that's why you pay a premium for a 3/4th inch chip instead of the 1/3rd inch P&S cameras. damn I want an SLR camera.

 

[NaOH]

Originally posted by: tfinch2

Originally posted by: Zenmervolt

Originally posted by: AMDUALY

Originally posted by: Aflac
if you don't get it before I get home, I'll take out my S3 and try a few things. The S3 isn't the best camera to make example pics, but it should work...

SLRs are the only ones that can create this affect to a degree where it is very noticeable.

Wrong. I can set my Olympus C-8080 at F2.4 and it'll create a nice bokeh behind the subject.

As long as you have manual control over the aperture offered, you can get the effect.

ZV

Sensor-size plays a big part in visible DoF in digital images.

No, manual control over aperature will not automatically produce that effect.

I have full manual control over my G5, including easy focusing with the function wheel. There is no way I would be able to get the same effect with my camera. I am not saying it isn't totally there (It definitely blurs when I'm up close to the object of course). There will still be a degree of "blur", but it is nothing compared to an slr.

 

[DBL]

Originally posted by: fuzzybabybunny
Just FYI, when you really want to get that background out of focus effect, you need a pretty large apertures like f/1.8, f/2.2, and f/2.5.

That's not completely true. Distance to subject is just as important. You can take a picture at 5.6 which had a more out of focus background than one taken at 1.8 just because there is greater separation between the subject and the background.

F/4 on a DSLR is good enough for experimenting with DOF. Just make sure that you create enough distance between the subject and the background.

 

[DBL]

Originally posted by: Feldenak

Originally posted by: BroeBo
Here is one of mine at 75mm f/4

http://www.pbase.com/broe/image/59584761/




Ah I see the D50 does not have the DOF preview button like the XT and D70

That's one thing I wish the D50 did have.

IMO, it's pretty much worthless anyway. You really can't get a feel for the final DOF, especially with the tiny viewfinders in cropped DSLR cameras.

 

[fuzzybabybunny]

Originally posted by: DBL

Originally posted by: fuzzybabybunny
Just FYI, when you really want to get that background out of focus effect, you need a pretty large apertures like f/1.8, f/2.2, and f/2.5.

That's not completely true. Distance to subject is just as important. You can take a picture at 5.6 which had a more out of focus background than one taken at 1.8 just because there is greater separation between the subject and the background.

F/4 on a DSLR is good enough for experimenting with DOF. Just make sure that you create enough distance between the subject and the background.

Right.... for experimenting. For practical purposes like portraiture, anything smaller than f/2.8 is kinda worthless, unless you actively seek backgrounds that are far away from the subject.

 

[NaOH]

I wish I could afford having an DSLR (buying one is nothing, buying the damn lenses is another story). Guess I'll have to make do with the G5 for a while longer.

 

[fuzzybabybunny]

Originally posted by: DBL

Originally posted by: Feldenak

Originally posted by: BroeBo
Here is one of mine at 75mm f/4

http://www.pbase.com/broe/image/59584761/




Ah I see the D50 does not have the DOF preview button like the XT and D70

That's one thing I wish the D50 did have.

IMO, it's pretty much worthless anyway. You really can't get a feel for the final DOF, especially with the tiny viewfinders in cropped DSLR cameras.

I can't live without my DOF preview button. For lenses nowadays that can't stop down manually via an aperture ring, the DOF preview button lets me stop down a lens for reverse mounting and macro shooting. But this is very specialized and kinda out there... I don't actually use the DOF preview button for its intended purposed, previewing the DOF...

 

[fuzzybabybunny]

Originally posted by: AMDUALY
I wish I could afford having an DSLR (buying one is nothing, buying the damn lenses is another story). Guess I'll have to make do with the G5 for a while longer.

What about that Pentax *ist deal in Hot Deals? Get yourself some old, cheap, but still optically excellent Pentax lenses, and you're good to go.

 

[Zenmervolt]

Originally posted by: AMDUALY

Originally posted by: tfinch2
Sensor-size plays a big part in visible DoF in digital images.

No, manual control over aperature will not automatically produce that effect.

I have full manual control over my G5, including easy focusing with the function wheel. There is no way I would be able to get the same effect with my camera. I am not saying it isn't totally there (It definitely blurs when I'm up close to the object of course). There will still be a degree of "blur", but it is nothing compared to an slr.

Point on the sensor size enhancing/diminishing the effect. Also, I tend to only work with that effect in close-up shots so I see more bokeh than I would if I were shooting objects at a greater distance.

I wonder though if it's really sensor size or if lens design plays a role as well. The crop factor on my little Olympus is almost 3.95x (lens is 7.1mm-35.6mm, equivalent to 28-140). I know for a fact that at a given F-stop my 24mm lens on my film camera has a larger DOF than my 300mm. A 7.1mm lens should have more DOF than the 24mm.

I'm still waiting for Nikon to release a full-frame camera. Zeiss is making F-Mount lenses now and I'm excited. Tempted to buy an old FM2N and start looking at the Zeiss F-Mounts...

ZV

 

[Feldenak]

Originally posted by: Zenmervolt

Originally posted by: AMDUALY

Originally posted by: tfinch2
Sensor-size plays a big part in visible DoF in digital images.

No, manual control over aperature will not automatically produce that effect.

I have full manual control over my G5, including easy focusing with the function wheel. There is no way I would be able to get the same effect with my camera. I am not saying it isn't totally there (It definitely blurs when I'm up close to the object of course). There will still be a degree of "blur", but it is nothing compared to an slr.

Point on the sensor size enhancing/diminishing the effect. Also, I tend to only work with that effect in close-up shots so I see more bokeh than I would if I were shooting objects at a greater distance.

I wonder though if it's really sensor size or if lens design plays a role as well. The crop factor on my little Olympus is almost 3.95x (lens is 7.1mm-35.6mm, equivalent to 28-140). I know for a fact that at a given F-stop my 24mm lens on my film camera has a larger DOF than my 300mm. A 7.1mm lens should have more DOF than the 24mm.

I'm still waiting for Nikon to release a full-frame camera. Zeiss is making F-Mount lenses now and I'm excited. Tempted to buy an old FM2N and start looking at the Zeiss F-Mounts...

ZV

Don't hold your breath.

 

[NaOH]

Originally posted by: fuzzybabybunny

Originally posted by: AMDUALY
I wish I could afford having an DSLR (buying one is nothing, buying the damn lenses is another story). Guess I'll have to make do with the G5 for a while longer.

What about that Pentax *ist deal in Hot Deals? Get yourself some old, cheap, but still optically excellent Pentax lenses, and you're good to go.

Price went up again =(

 

[pontifex]

Originally posted by: AMDUALY

Originally posted by: pontifex

Originally posted by: fuzzybabybunny

Originally posted by: pontifex

Originally posted by: Aflac
IIRC, if you want a more specific part of a picture in focus, you want a lower depth of field, but you have to make sure the subject is the part in focus. Try taking a pic with manual focus, it's easier to control for taking a stationary pic. However, it depends on how much space there is between the subject and the background.

one of the examples the author used was this middle eastern man as a close up portrait shot but in the background (about 8-10 ft away i would guess) is another man in front of a wall. main subject was in focus but the wall and other man were out of focus.

Just FYI, when you really want to get that background out of focus effect, you need a pretty large apertures like f/1.8, f/2.2, and f/2.5.

well, the author said he was using f4 for the example pic i was referring to, unless that was a typo.

I thought you needed a smaller aperature, hence an f-stop of 4 and up.

i tried higher f-stops also and got the same result

 

[pontifex]

Originally posted by: DBL

Originally posted by: fuzzybabybunny
Just FYI, when you really want to get that background out of focus effect, you need a pretty large apertures like f/1.8, f/2.2, and f/2.5.

That's not completely true. Distance to subject is just as important. You can take a picture at 5.6 which had a more out of focus background than one taken at 1.8 just because there is greater separation between the subject and the background.

F/4 on a DSLR is good enough for experimenting with DOF. Just make sure that you create enough distance between the subject and the background.

that may be my problem, because i don't think there was that much distance.