Bokeh doubt (50mm vs 24mm)

[Meredoth]

Hello all!

Let's say I have both 50mm and 24mm, the STM ones from Canon. If I record a video (same settings, light, etc.) with those lenses, both at f/4, will the bokeh be different?

I know the bokeh of 50mm is better but is it better only at 1.8, since the 24mm is just 2.8?

I also read here and there that the 1.8 of the STM lens is not that good. What are your guys opinion? I already have the 24mm, wondering if I should get the 50mm. My main goal is video, and though it's indoors, I have the space for the 50mm.

Thanks!

 

[480sparky]

Every lens renders bokeh differently.

 

[photo1x1.com]

A lens with a longer focal length will always have shallower depth of field. So at f4 - both will definitely have a very different amount of blur (the 50mm having much more). You sure have a zoom lens (maybe a kit lens that came with your camera body). Try that at the same f-stop at 24mm and 50mm, and see for yourself.
The much more apparent difference will be the distortion and angle of view though. A 24mm lens renders images very differently than a 50mm lens does.

Regarding bokeh: if you take several different 50mm lenses, they all will roughly render the same amount of background blur at the same f-stop. But the "quality" of the blur will be different. Some are smoother, but others will show the shape of the aperture opening (if it is not completely round).

 

[Meredoth]

A lens with a longer focal length will always have shallower depth of field. So at f4 - both will definitely have a very different amount of blur (the 50mm having much more). You sure have a zoom lens (maybe a kit lens that came with your camera body). Try that at the same f-stop at 24mm and 50mm, and see for yourself.
The much more apparent difference will be the distortion and angle of view though. A 24mm lens renders images very differently than a 50mm lens does.

Regarding bokeh: if you take several different 50mm lenses, they all will roughly render the same amount of background blur at the same f-stop. But the "quality" of the blur will be different. Some are smoother, but others will show the shape of the aperture opening (if it is not completely round).

I see. That's some good news, and I guess it makes the purchase of the 50mm STM worth it, even though I already have the 24mm.

And I actually do not have the kit lens, I got the camera body only and used the money to get my 24mm.

 

[photo1x1.com]

A lens with a longer focal length will always have shallower depth of field. So at f4 - both will definitely have a very different amount of blur (the 50mm having much more). You sure have a zoom lens (maybe a kit lens that came with your camera body). Try that at the same f-stop at 24mm and 50mm, and see for yourself.
The much more apparent difference will be the distortion and angle of view though. A 24mm lens renders images very differently than a 50mm lens does.

Regarding bokeh: if you take several different 50mm lenses, they all will roughly render the same amount of background blur at the same f-stop. But the "quality" of the blur will be different. Some are smoother, but others will show the shape of the aperture opening (if it is not completely round).

I see. That's some good news, and I guess it makes the purchase of the 50mm STM worth it, even though I already have the 24mm.

And I actually do not have the kit lens, I got the camera body only and used the money to get my 24mm.

Which type of camera do you have full format, or crop? I can make a testimage for you if you like.

 

[Meredoth]

A lens with a longer focal length will always have shallower depth of field. So at f4 - both will definitely have a very different amount of blur (the 50mm having much more). You sure have a zoom lens (maybe a kit lens that came with your camera body). Try that at the same f-stop at 24mm and 50mm, and see for yourself.
The much more apparent difference will be the distortion and angle of view though. A 24mm lens renders images very differently than a 50mm lens does.

Regarding bokeh: if you take several different 50mm lenses, they all will roughly render the same amount of background blur at the same f-stop. But the "quality" of the blur will be different. Some are smoother, but others will show the shape of the aperture opening (if it is not completely round).

I see. That's some good news, and I guess it makes the purchase of the 50mm STM worth it, even though I already have the 24mm.

And I actually do not have the kit lens, I got the camera body only and used the money to get my 24mm.

Which type of camera do you have full format, or crop? I can make a testimage for you if you like.

Oh, that would be nice! I have a SL2, cropped.

 

[photo1x1.com]

A lens with a longer focal length will always have shallower depth of field. So at f4 - both will definitely have a very different amount of blur (the 50mm having much more). You sure have a zoom lens (maybe a kit lens that came with your camera body). Try that at the same f-stop at 24mm and 50mm, and see for yourself.
The much more apparent difference will be the distortion and angle of view though. A 24mm lens renders images very differently than a 50mm lens does.

Regarding bokeh: if you take several different 50mm lenses, they all will roughly render the same amount of background blur at the same f-stop. But the "quality" of the blur will be different. Some are smoother, but others will show the shape of the aperture opening (if it is not completely round).

I see. That's some good news, and I guess it makes the purchase of the 50mm STM worth it, even though I already have the 24mm.

And I actually do not have the kit lens, I got the camera body only and used the money to get my 24mm.

Which type of camera do you have full format or crop? I can make a test image for you if you like.

Oh, that would be nice! I have a SL2, cropped.

OK, here we go. There is nothing fancy going on here at the moment, so the images are not spectacular .
To explain: my old 400D battery was dead, so I had to use a full frame body and cropped the middle - that would render exactly the same image than shooting from a crop format sensor. The lenses I used were Sigma 50mm F1,4 EX DG HSM (at f1.8!!!) and Canon 24mm f1.4 LII (at f2.8!!!) to give you the depth of field of the lenses you are considering or owning. As said above - the bokeh is something different, we are only talking about depth of field and background blur.

Image Nr. 1: 50mm @f1.8 (click to enlarge)

Image Nr. 2: 24mm @f2.8

Both of the above images were shot from a tripod, same position - only the lens was changed.
To give you an even better idea, I also took a shot with the 24mm and moved closer to the subject so that the crop of the main subject is roughly the same.
Image Nr. 3: 24mm @f2.8 from a closer distance


I hope that helps you with you with your decision. Keep in mind that things change when you move your subject or the background:

• the closer your subject is to the camera the more blurred your background
• the further away your background from your subject, the more blurred the background

And here are the other factors that blur the background:

• a wider aperture (lower number): more blur
  
• a larger sensor (because you move closer to frame the subject): more blur
  
• a longer focal length: more blur

 

[Meredoth]

A lens with a longer focal length will always have shallower depth of field. So at f4 - both will definitely have a very different amount of blur (the 50mm having much more). You sure have a zoom lens (maybe a kit lens that came with your camera body). Try that at the same f-stop at 24mm and 50mm, and see for yourself.
The much more apparent difference will be the distortion and angle of view though. A 24mm lens renders images very differently than a 50mm lens does.

Regarding bokeh: if you take several different 50mm lenses, they all will roughly render the same amount of background blur at the same f-stop. But the "quality" of the blur will be different. Some are smoother, but others will show the shape of the aperture opening (if it is not completely round).

I see. That's some good news, and I guess it makes the purchase of the 50mm STM worth it, even though I already have the 24mm.

And I actually do not have the kit lens, I got the camera body only and used the money to get my 24mm.

Which type of camera do you have full format or crop? I can make a test image for you if you like.

Oh, that would be nice! I have a SL2, cropped.

OK, here we go. There is nothing fancy going on here at the moment, so the images are not spectacular .
To explain: my old 400D battery was dead, so I had to use a full frame body and cropped the middle - that would render exactly the same image than shooting from a crop format sensor. The lenses I used were Sigma 50mm F1,4 EX DG HSM (at f1.8!!!) and Canon 24mm f1.4 LII (at f2.8!!!) to give you the depth of field of the lenses you are considering or owning. As said above - the bokeh is something different, we are only talking about depth of field and background blur.

Image Nr. 1: 50mm @f1.8 (click to enlarge)
View attachment 150015
Image Nr. 2: 24mm @f2.8
View attachment 150016
Both of the above images were shot from a tripod, same position - only the lens was changed.
To give you an even better idea, I also took a shot with the 24mm and moved closer to the subject so that the crop of the main subject is roughly the same.
Image Nr. 3: 24mm @f2.8 from a closer distance
View attachment 150017

I hope that helps you with you with your decision. Keep in mind that things change when you move your subject or the background:

• the closer your subject is to the camera the more blurred your background
• the further away your background from your subject, the more blurred the background

And here are the other factors that blur the background:

• a wider aperture (lower number): more blur
  
• a larger sensor (because you move closer to frame the subject): more blur
  
• a longer focal length: more blur

Hey, many thanks for the post!!! Really helpful! And the shots are really cool!

One thing that I'm doubt is that comparing pictures 1 and 3, even though the subject is "framed" (not sure if it's the right term) the same way, the background is different. On the first picture it's possible to see only the top of door and windows, while in picture 3 it's possible to see much more like the balcony.

Was my understanding that getting close to the subject (with a different lens) would eventually give the same... content on the picture. Guess I was wrong? hehe

 

[JonA_CT]

The autofocus on the Canon 50mm f1.8 is stupid loud, if that helps your decision at all. I'd call it almost unusable if you are using the on-board microphone.

 

[photo1x1.com]

A lens with a longer focal length will always have shallower depth of field. So at f4 - both will definitely have a very different amount of blur (the 50mm having much more). You sure have a zoom lens (maybe a kit lens that came with your camera body). Try that at the same f-stop at 24mm and 50mm, and see for yourself.
The much more apparent difference will be the distortion and angle of view though. A 24mm lens renders images very differently than a 50mm lens does.

Regarding bokeh: if you take several different 50mm lenses, they all will roughly render the same amount of background blur at the same f-stop. But the "quality" of the blur will be different. Some are smoother, but others will show the shape of the aperture opening (if it is not completely round).

I see. That's some good news, and I guess it makes the purchase of the 50mm STM worth it, even though I already have the 24mm.

And I actually do not have the kit lens, I got the camera body only and used the money to get my 24mm.

Which type of camera do you have full format or crop? I can make a test image for you if you like.

Oh, that would be nice! I have a SL2, cropped.

OK, here we go. There is nothing fancy going on here at the moment, so the images are not spectacular .
To explain: my old 400D battery was dead, so I had to use a full frame body and cropped the middle - that would render exactly the same image than shooting from a crop format sensor. The lenses I used were Sigma 50mm F1,4 EX DG HSM (at f1.8!!!) and Canon 24mm f1.4 LII (at f2.8!!!) to give you the depth of field of the lenses you are considering or owning. As said above - the bokeh is something different, we are only talking about depth of field and background blur.

Image Nr. 1: 50mm @f1.8 (click to enlarge)
View attachment 150015
Image Nr. 2: 24mm @f2.8
View attachment 150016
Both of the above images were shot from a tripod, same position - only the lens was changed.
To give you an even better idea, I also took a shot with the 24mm and moved closer to the subject so that the crop of the main subject is roughly the same.
Image Nr. 3: 24mm @f2.8 from a closer distance
View attachment 150017

I hope that helps you with you with your decision. Keep in mind that things change when you move your subject or the background:

• the closer your subject is to the camera the more blurred your background
• the further away your background from your subject, the more blurred the background

And here are the other factors that blur the background:

• a wider aperture (lower number): more blur
  
• a larger sensor (because you move closer to frame the subject): more blur
  
• a longer focal length: more blur

Hey, many thanks for the post!!! Really helpful! And the shots are really cool!

One thing that I'm doubt is that comparing pictures 1 and 3, even though the subject is "framed" (not sure if it's the right term) the same way, the background is different. On the first picture it's possible to see only the top of door and windows, while in picture 3 it's possible to see much more like the balcony.

Was my understanding that getting close to the subject (with a different lens) would eventually give the same... content on the picture. Guess I was wrong? hehe

Hahaha, If there is one thing that I doubt then it is, that the shots are cool .
Every focal length has a different field of view. So getting closer to framing the foreground in image 3 didn´t have much influence on the background.
To understand that, get outdoors, and look through an empty roll of toilet paper to narrow your field of view.
Now walk towards a car that is rather near. You will see that you will soon only see parts of the car.
But you will also see that while the small walking distance had such a big influence on the close object, it only has minimal influence on things that are far away.
If you walked 5m towards the car, you might now only see the keyhole. But if you had a wide open field and walked the same 5m, you would still have almost the same view through your toilet paper roll.

Stupid example, but does that make sense for you?

 

[Braineack]

One thing that I'm doubt is that comparing pictures 1 and 3, even though the subject is "framed" (not sure if it's the right term) the same way, the background is different. On the first picture it's possible to see only the top of door and windows, while in picture 3 it's possible to see much more like the balcony.

Was my understanding that getting close to the subject (with a different lens) would eventually give the same... content on the picture. Guess I was wrong? hehe

this is exactly what I'd expect to see when shooting 50mm vs. 24mm...

 

[KmH]

Don't make the very common mistake thinking that bokeh and depth-of-field are the same thing, because they aren't.
Bokeh cannot be adjusted and is an inherent property of each make/model of lens.
Depth-of-field is adjustable and is controlled mainly by point of focus distance though lens aperture, image sensor size, and lens focal length factor in.

 

[TCampbell]

As Keith points out... Bokeh refers the the quality (not quantity) of out-of-focus blur. I can pick on the Canon EF 50mm lenses as an example...

Previously Canon’s “nifty fifty” was a 50mm f/1.8 lens that only had 5 aperture blades. A de-focused point of light will blur to the shape of the aperture blade. So if the aperture is 5 blades that aren’t well-rounded, you get pentagonal shapes. With this particular lens, everything blurred to that shape and the over-lapping texture gave it a quality that wasn’t very smooth (sometimes described as “jittery” bokeh or even “nervous” bokeh).

Canon’s current “nifty fifty” was redesigned, now uses the STM focusing motor, and uses 7 aperture blades and is a bit more well-rounded. Out of focus blur is closer to a circle than a pentagon and the quality of the out-of-focus blur is substantially improved over the previous generation.

More aperture blades and having well-rounded aperture blades is a factor that influences bokeh... but qualities of the optics themselves also control this. If you imagine the curved front surface of your lens with the very center as representing the “North Pole” with lines of longitude moving away from center, and lines of latitude circling around the center. But in photography the lines that radiate away from the center (like bicycle spokes) are called “sagital” lines and the lines that go around the center (like concentric rings) are called “meridonal” lines. It turns out some lenses blur more strongly in one direction than in the other.

Lomography makes a lens they call the “Petzval” which is meant to be something of a reproduction of an old lens (it’s got a brass barrel, completely manual, and instead of aperture blades that constrict and retract it comes with a set of metal plates that slide into the side of the lens — each having a different size hole. These are called “Waterhouse stops” and it’s how they control the aperture size). But the stops are perfectly round drilled holes. But it turns out the bokeh quality of this particular lens creates a swirl effect because the lens blurs more strongly in the meridonal direction than in the sagital direction. This is just one example of how the optics themselves ... and not the shape of the aperture ... control the quality of the blur.

So again... “bokeh” refers to the quality of the blur... not how strongly it blurs.

Depth of field controls the strength of the out-of-focus blur (regardless of whether or not you like the quality of the blur.)

Factors that influence the strength of the out of focus blur are:

1) close subject - distant background (so the focus distance to those elements of your shot are not similar).
2) long focal length lens - very long focal lengths naturally produce a shallower focal ratio. Very short lenses (ultra-wide lenses) have very very broad depth of field and you wont get strong out-of-focus blur.
3) low focal-ratio - using a low f-stop (large aperture opening) causes light to use more of the “glass”. Narrow focal ratios cause light to go only through the center of the lens. It turns out you’ll get stronger out-of-focus blur (significantly stronger) with a low focal ratio (provided it’s also not a short focal length).

A 24mm lens will have a low amount of out-of-focus blur and it’s probably not what you want.

A 50mm lens will have more out-of-focus blur (provided you shoot at a low focal ratio such as f/2 or f/1.8).

If you want STRONG out of focus blur, consider moving to a longer lens... such as an 85mm f/1.8 ... or a 135mm f/2 ... the 70-200mm f/2.8 generates strong bokeh at the 200mm end. I have a 300mm f/2.8 lens which generates so much sweet creaminess in the image that it’ll give you diabetes. ;-)

 

[Meredoth]

A lens with a longer focal length will always have shallower depth of field. So at f4 - both will definitely have a very different amount of blur (the 50mm having much more). You sure have a zoom lens (maybe a kit lens that came with your camera body). Try that at the same f-stop at 24mm and 50mm, and see for yourself.
The much more apparent difference will be the distortion and angle of view though. A 24mm lens renders images very differently than a 50mm lens does.

Regarding bokeh: if you take several different 50mm lenses, they all will roughly render the same amount of background blur at the same f-stop. But the "quality" of the blur will be different. Some are smoother, but others will show the shape of the aperture opening (if it is not completely round).

I see. That's some good news, and I guess it makes the purchase of the 50mm STM worth it, even though I already have the 24mm.

And I actually do not have the kit lens, I got the camera body only and used the money to get my 24mm.

Which type of camera do you have full format or crop? I can make a test image for you if you like.

Oh, that would be nice! I have a SL2, cropped.

OK, here we go. There is nothing fancy going on here at the moment, so the images are not spectacular .
To explain: my old 400D battery was dead, so I had to use a full frame body and cropped the middle - that would render exactly the same image than shooting from a crop format sensor. The lenses I used were Sigma 50mm F1,4 EX DG HSM (at f1.8!!!) and Canon 24mm f1.4 LII (at f2.8!!!) to give you the depth of field of the lenses you are considering or owning. As said above - the bokeh is something different, we are only talking about depth of field and background blur.

Image Nr. 1: 50mm @f1.8 (click to enlarge)
View attachment 150015
Image Nr. 2: 24mm @f2.8
View attachment 150016
Both of the above images were shot from a tripod, same position - only the lens was changed.
To give you an even better idea, I also took a shot with the 24mm and moved closer to the subject so that the crop of the main subject is roughly the same.
Image Nr. 3: 24mm @f2.8 from a closer distance
View attachment 150017

I hope that helps you with you with your decision. Keep in mind that things change when you move your subject or the background:

• the closer your subject is to the camera the more blurred your background
• the further away your background from your subject, the more blurred the background

And here are the other factors that blur the background:

• a wider aperture (lower number): more blur
  
• a larger sensor (because you move closer to frame the subject): more blur
  
• a longer focal length: more blur

Hey, many thanks for the post!!! Really helpful! And the shots are really cool!

One thing that I'm doubt is that comparing pictures 1 and 3, even though the subject is "framed" (not sure if it's the right term) the same way, the background is different. On the first picture it's possible to see only the top of door and windows, while in picture 3 it's possible to see much more like the balcony.

Was my understanding that getting close to the subject (with a different lens) would eventually give the same... content on the picture. Guess I was wrong? hehe

Hahaha, If there is one thing that I doubt then it is, that the shots are cool .
Every focal length has a different field of view. So getting closer to framing the foreground in image 3 didn´t have much influence on the background.
To understand that, get outdoors, and look through an empty roll of toilet paper to narrow your field of view.
Now walk towards a car that is rather near. You will see that you will soon only see parts of the car.
But you will also see that while the small walking distance had such a big influence on the close object, it only has minimal influence on things that are far away.
If you walked 5m towards the car, you might now only see the keyhole. But if you had a wide open field and walked the same 5m, you would still have almost the same view through your toilet paper roll.

Stupid example, but does that make sense for you?

It's like magic!!! But I did not run outside with an empty roll of paper. Though I used my own hand at home to see it. hehehe

As Keith points out... Bokeh refers the the quality (not quantity) of out-of-focus blur. I can pick on the Canon EF 50mm lenses as an example...

Previously Canon’s “nifty fifty” was a 50mm f/1.8 lens that only had 5 aperture blades. A de-focused point of light will blur to the shape of the aperture blade. So if the aperture is 5 blades that aren’t well-rounded, you get pentagonal shapes. With this particular lens, everything blurred to that shape and the over-lapping texture gave it a quality that wasn’t very smooth (sometimes described as “jittery” bokeh or even “nervous” bokeh).

Canon’s current “nifty fifty” was redesigned, now uses the STM focusing motor, and uses 7 aperture blades and is a bit more well-rounded. Out of focus blur is closer to a circle than a pentagon and the quality of the out-of-focus blur is substantially improved over the previous generation.

More aperture blades and having well-rounded aperture blades is a factor that influences bokeh... but qualities of the optics themselves also control this. If you imagine the curved front surface of your lens with the very center as representing the “North Pole” with lines of longitude moving away from center, and lines of latitude circling around the center. But in photography the lines that radiate away from the center (like bicycle spokes) are called “sagital” lines and the lines that go around the center (like concentric rings) are called “meridonal” lines. It turns out some lenses blur more strongly in one direction than in the other.

Lomography makes a lens they call the “Petzval” which is meant to be something of a reproduction of an old lens (it’s got a brass barrel, completely manual, and instead of aperture blades that constrict and retract it comes with a set of metal plates that slide into the side of the lens — each having a different size hole. These are called “Waterhouse stops” and it’s how they control the aperture size). But the stops are perfectly round drilled holes. But it turns out the bokeh quality of this particular lens creates a swirl effect because the lens blurs more strongly in the meridonal direction than in the sagital direction. This is just one example of how the optics themselves ... and not the shape of the aperture ... control the quality of the blur.

So again... “bokeh” refers to the quality of the blur... not how strongly it blurs.

Depth of field controls the strength of the out-of-focus blur (regardless of whether or not you like the quality of the blur.)

Factors that influence the strength of the out of focus blur are:

1) close subject - distant background (so the focus distance to those elements of your shot are not similar).
2) long focal length lens - very long focal lengths naturally produce a shallower focal ratio. Very short lenses (ultra-wide lenses) have very very broad depth of field and you wont get strong out-of-focus blur.
3) low focal-ratio - using a low f-stop (large aperture opening) causes light to use more of the “glass”. Narrow focal ratios cause light to go only through the center of the lens. It turns out you’ll get stronger out-of-focus blur (significantly stronger) with a low focal ratio (provided it’s also not a short focal length).

A 24mm lens will have a low amount of out-of-focus blur and it’s probably not what you want.

A 50mm lens will have more out-of-focus blur (provided you shoot at a low focal ratio such as f/2 or f/1.8).

If you want STRONG out of focus blur, consider moving to a longer lens... such as an 85mm f/1.8 ... or a 135mm f/2 ... the 70-200mm f/2.8 generates strong bokeh at the 200mm end. I have a 300mm f/2.8 lens which generates so much sweet creaminess in the image that it’ll give you diabetes. ;-)

Thanks for the in-depth explanation! Already ordered the 50mm STM, hope to get it till Friday. It will give me, with the 24mm, nice flexibility for what I need, I suppose. After that, maybe saving some money for a Sigma lens. *.*