DOF On Four Thirds

[OlyFlyer]

4/3 can do very shallow DOF on small objects. No doubt about it. But when it comes to half body and full body portraits, it's going to be very expensive. Also, the lens will be very bulky.

Not true. DOF is also dependent on distance. Of course, if you want to take a half body, you can not stand a half meter from the model, but similarily, the background must be further back as well. There is no camera in the world which can take half body images from a half meter and yet have narrow DOF. I remember your kind of arguments from dpr about small objects, and they just don't hold. Just calculate the DOF for different lenses and you will see. If you want narrow DOF for half body, and you think the 50/f2 is not good enough, get the 50-200. It is still the case that the 50mm is actually a little too short for portraits in my opinion. Of course, if you want a really narrow DOF, and you have the money, the 35-100/f2 or the 150/f2 is even better.

 

[OlyFlyer]

In Olyflyer's case, bringing the foreground closer to the lens and in Schon's case, placing background further away from the lens.

In fact, in my case, both foreground and background is blurred. Only the middle marble is in focus.

 

[Clockunder]

Yes, I am aware of this, but again, the variation is really in the object distance.

But you were earlier unable to see retrovox's main point that subject size will affect the focal length or shooting distance used and thus is related to the DOF indirectly.

I think you have missed the salient point.

If the subject is bigger, you have no choice but to stand further or use a shorter focal length and this affects DOF.

It's better to illustrate with an e.g.

Shooting a small round ball which is 2cm in radius or 4cm in diameter.

If you use a 4/3 camera with 50mm lens and you want the whole of this small ball to be within the frame.

For simplicity, 4/3 sensor size is assumed to be 18mm x 13.5mm (although I know it's 17.3mm x 13mm).

So you can stand at about (lens to subject distance):

40mm/13.5mm x 50mm = 148mm or 14.8cm away. (At this distance, the 40mm diameter ball's image on the sensor will be 13.5mm in diameter and can fit into the 18mm x 13.5mm 4/3 system sensor).

At F/2, DOF = 0.03cm or 0.3mm ====> very shallow.

Alternatively, you use 100mm instead of 50mm but now need to stand at :

40mm/13.5mm x 100mm = 296mm or 29.6cm away. (At this new distance, the 40mm diameter ball's image will again be 13.5mm on the image sensor but this time with a 100mm lens instead of 50mm).

DOF of F/2, 100mm from 29.6cm away = 0.03cm or 0.3mm again. (i.e. same as earlier with 50mm lens).

In fact, you will end up with the same DOF regardless of focal lengths or shooting distance if you want to maintain the same subject size on the image sensor. This is because the DOF effect resulting from the variation of focal lengths will be exactly offset by the DOF effect from a necessary change in shooting distance. So practically, the key is to DOF is only the aperture.


Now if the subject is now a 1m tall half body and you want to have it in portrait framing with your 50mm, you would need to stand about :

1000mm/18mm x 50mm = 2.78m or 2780mm away

At F/2, DOF = 18.2cm or 182mm (vs earlier 0.03cm or 0.3mm DOF).

(Again if you were to use 100mm instead of 50mm, you would need to stand at 5.6m (i.e. double the original distance) and the DOF will still be 18.2cm.

===
Now, the implication of the above is that it is actually the composition which determines the DOF and composition is very closely related to subject size.

With a bigger subject, you have to either a) if you use the same focal length, stand further or b) if you stand at the same distance, use a shorter focal length.

In any case, for bigger subject, you won't be able to achieve the kind of shallow DOF achievable with small subjects as the combination of focal length and shooting distance necessary for bigger subject will mean a greater DOF.

So the salient point is : The bigger the subject is, the more DOF because of the above.

(if you shoot a 70-storey building which is about 210m tall and you use 50mm, you would need to stand : 210,000mm/18mm x 50mm = 583m away. Even if you use F/1, your DOF is still infinite. Compare this to the shallow DOF shooting a small 4cm diameter ball and you will see why subject size very much determines the DOF.).

====
Compare the DOF on the full frame for the 1m half body subject and a 50mm lens. You would need to stand at about :

1000mm/36mm x 50mm = 1.39m or 139cm

At F/2, DOF (full frame) = 8.95cm or 89.5mm (vs 18.2cm on 4/3).

To achieve this kind of shallow DOF with a 50mm lens on the 4/3 system, you would need a F/1 lens. In fact, the DOF of 50mm at F/2 50mm on 4/3 system is equal to the DOF of 50mm at F/4 on the full frame.

Basically, the smaller the image sensor, the bigger the aperture is required for shallower DOF. Bigger aperture means more costly.

 

[onedollar]

If you want great DOF out of the min. money you want to spend, maybe you can consider a Sigma 30mm f1.4.

Will try some more on 105mm f2.8 when it arrives.

 

[retrovox]

Maybe it's better to illustrate with examples. Please take a look at some of the photos shot by Jessica Claire via this link: http://www.jessicaclaire.net/index.cfm?m=12&y=2007&StartRow=11

Under the post: DREW AND CHUCK ARE EXPECTING!, one can clearly see the shallow DOF rendered in her full body portrait photos. And so, I'm thinking if Zuiko 50 200 f2.8-3.5 can allow me to do this effect. I'm sure the Zuiko 35 100 f2 and 150 f2 could do this, but they are way too expensive and bulky.

So, one might argue saying, what for you want such shallow DOF...focusing will be very difficult etc. I understand the above issues and that different people have different DOF preference. It's just a matter of personal taste. But my frustration is on the lack of fast primes from Zuiko that robs me the opportunity to unleash such creativity when the situation calls for it. Whether the DOF is shallow enough or not, and whether focusing is an issue or not, it's another story altogether.

Consider the fast primes from Pentax's 85mm f1.4, 77mm f1.8 limited. They are excellent lenses for doing full body portraits. Moreover, they are not too bulky nor unaffordable. I think what Zuiko can offer to compensate for the additional DOF due to smaller sensor size, is to make faster lens i.e. f1.2, f1.4, f1.8 etc more affordable than the competition. It will be even better if they can make them more compact and lighter as what 4/3 always claims they are capable of doing.

 

[microcosm]

Just want to add that her pages has images that are heavily PS-ed. Bokeh can be created if one is good in Photoshop... so please, shooting is only 50% of the work... Let me demonstrate this to you guys at the next kopi session about creating bokeh in Photoshop...

Thanks for linking Jessica Claire's page.

 

[retrovox]

Just want to add that her pages has images that are heavily PS-ed. Bokeh can be created if one is good in Photoshop... so please, shooting is only 50% of the work... Let me demonstrate this to you guys at the next kopi session about creating bokeh in Photoshop...

Thanks for linking Jessica Claire's page.

Yup. Her photos are heavily processed. I read that she uses Canon 85mm f1.2. I think that really helps her to make the subject more stand out. I don't rule out the possibility of using image editing software to create fake DOF in her photos though.

 

[onedollar]

As i shown in the picture above, i am sitting at the back of the taxi. you can imagine the distance the camera from the front seat pillow and from the pillow to the front window.

 

[halcy0n]

I do not disagree with you but to attribute DOF to the object size is an inaccurate statement. My salient point is that the size of an object does not affect DOF. The greater DOF is a resultant effect because you choose to vary the object distance. Such a statement is akin to saying the DOF depends on what the weather is like for the day.

But you were earlier unable to see retrovox's main point that subject size will affect the focal length or shooting distance used and thus is related to the DOF indirectly.

I think you have missed the salient point.

If the subject is bigger, you have no choice but to stand further or use a shorter focal length and this affects DOF.

It's better to illustrate with an e.g.

Shooting a small round ball which is 2cm in radius or 4cm in diameter.

If you use a 4/3 camera with 50mm lens and you want the whole of this small ball to be within the frame.

For simplicity, 4/3 sensor size is assumed to be 18mm x 13.5mm (although I know it's 17.3mm x 13mm).

So you can stand at about (lens to subject distance):

40mm/13.5mm x 50mm = 148mm or 14.8cm away. (At this distance, the 40mm diameter ball's image on the sensor will be 13.5mm in diameter and can fit into the 18mm x 13.5mm 4/3 system sensor).

At F/2, DOF = 0.03cm or 0.3mm ====> very shallow.

Alternatively, you use 100mm instead of 50mm but now need to stand at :

40mm/13.5mm x 100mm = 296mm or 29.6cm away. (At this new distance, the 40mm diameter ball's image will again be 13.5mm on the image sensor but this time with a 100mm lens instead of 50mm).

DOF of F/2, 100mm from 29.6cm away = 0.03cm or 0.3mm again. (i.e. same as earlier with 50mm lens).

In fact, you will end up with the same DOF regardless of focal lengths or shooting distance if you want to maintain the same subject size on the image sensor. This is because the DOF effect resulting from the variation of focal lengths will be exactly offset by the DOF effect from a necessary change in shooting distance. So practically, the key is to DOF is only the aperture.


Now if the subject is now a 1m tall half body and you want to have it in portrait framing with your 50mm, you would need to stand about :

1000mm/18mm x 50mm = 2.78m or 2780mm away

At F/2, DOF = 18.2cm or 182mm (vs earlier 0.03cm or 0.3mm DOF).

(Again if you were to use 100mm instead of 50mm, you would need to stand at 5.6m (i.e. double the original distance) and the DOF will still be 18.2cm.

===
Now, the implication of the above is that it is actually the composition which determines the DOF and composition is very closely related to subject size.

With a bigger subject, you have to either a) if you use the same focal length, stand further or b) if you stand at the same distance, use a shorter focal length.

In any case, for bigger subject, you won't be able to achieve the kind of shallow DOF achievable with small subjects as the combination of focal length and shooting distance necessary for bigger subject will mean a greater DOF.

So the salient point is : The bigger the subject is, the more DOF because of the above.

(if you shoot a 70-storey building which is about 210m tall and you use 50mm, you would need to stand : 210,000mm/18mm x 50mm = 583m away. Even if you use F/1, your DOF is still infinite. Compare this to the shallow DOF shooting a small 4cm diameter ball and you will see why subject size very much determines the DOF.).

====
Compare the DOF on the full frame for the 1m half body subject and a 50mm lens. You would need to stand at about :

1000mm/36mm x 50mm = 1.39m or 139cm

At F/2, DOF (full frame) = 8.95cm or 89.5mm (vs 18.2cm on 4/3).

To achieve this kind of shallow DOF with a 50mm lens on the 4/3 system, you would need a F/1 lens. In fact, the DOF of 50mm at F/2 50mm on 4/3 system is equal to the DOF of 50mm at F/4 on the full frame.

Basically, the smaller the image sensor, the bigger the aperture is required for shallower DOF. Bigger aperture means more costly.

 

[wind30]

it all makes me wonder why olympus made a 50mm f2 macro lens instead of a 50mm f1.4 lens. We all know that 50mm f1.4 lens is simple to make and not expensive. I personally think that there are more people who take portraits (ie wants less DOF) than people who takes macro.

Or why olympus did not have a 50mm 1.4 lens.... but the 50mm f2 is not too bad... but for people like me who never takes macro, I am paying more for a function which I never use and furthermore it doesn't come with a focus limiter so it makes the AF super slow if it decides to hunt.

 

[Clockunder]

I do not disagree with you but to attribute DOF to the object size is an inaccurate statement. My salient point is that the size of an object does not affect DOF. The greater DOF is a resultant effect because you choose to vary the object distance. Such a statement is akin to saying the DOF depends on what the weather is like for the day.

You may not want to agree but facts are facts. The numbers shown are not what I make out subjectively but based on facts.

Can you tell me how you're going to get shallow DOF for a building that is 210m tall and you want to have the whole building vertically up in your picture? I'm sure you can't. To include a building this tall, you definitely have to shoot further than the hyperfocal distance regardless of your focal length and aperture.

I can easily show you how to get a shallow DOF for any very small objects. Even a compact camera can do it.

For a 1m half body shot and you use 50mm, you have no choice but to stand at about 2.8m away. If you use 100mm, you have no choice but to stand 5.6m away. If you use 25mm, you have no choice but to stand 1.4m away. If you use 200mm, you have no choice but to stand 11.2m away. You may vary the distance and focal length but the DOFs are all the same if the same F number is used for aperture.

But if it's a 10cm half body shot for a small figurine instead, you can achieve a shallow DOF. Again, those afore-mentioned principles which apply for a 1m half body shot in shooting distances and focal length also apply here. This means that there are fixed combinations of focal lengths and distances which you have no choice but to use to achieve the "half body" and their DOFs are all the same if the same F number is used. Compared to the 1m half body, the DOF is much shallower here even though the composition is the same for 1m and 10cm half body.

From the above, it is clear that it is the subject size which indirectly determines the DOF simply because subject size determines the focal length - distance combination you require for the composition. Furthermore, if you want a certain perspective, your distance will be fixed and hence, you have no choice on focal length already. This is photography 101.

Mathematically, DOF is based on distance and focal length but practically, it's actually based on subject size other than aperture. Practically, since one cannot chose the subject size (if a building is 210m tall, you can't change it and if a person is 1.8m tall, you can't change it too. You can't tell the 1.8m person to become 18cm just because you can shoot nearer and have a shallow DOF for his/her half body shots, can you? Hahahaha. Even if you vary your focal length, this is only 1 distance for your half body shot for each focal length you choose and the DOF will be the same.), one can only try to vary the DOF through aperture in practice.

Facts are facts even if you don't agree. :bsmilie:

 

[Clockunder]

it all makes me wonder why olympus made a 50mm f2 macro lens instead of a 50mm f1.4 lens. We all know that 50mm f1.4 lens is simple to make and not expensive. I personally think that there are more people who take portraits (ie wants less DOF) than people who takes macro.

Or why olympus did not have a 50mm 1.4 lens.... but the 50mm f2 is not too bad... but for people like me who never takes macro, I am paying more for a function which I never use and furthermore it doesn't come with a focus limiter so it makes the AF super slow if it decides to hunt.

As you definitely already know, one of the touted advantages of the 4/3 system is "Brighter lenses by approximately two f-stops with same depth of field as 35mm lenses". (This is sometimes erroneously interpreted by some as the ability to have 2 stops more exposure for the same F number when compared to the 35mm full frame system when it only actually means 2-stop more DOF for the same F number.).

If it's F/1.4, it would have the same DOF as F/2.8 on 35mm full frame.

Are people in 4/3 system willing to pay $400-$600 (price range of Canon and Nikon 50mm F/1.4) to get shallower DOF only similar to F/2.8 on full frame and when it can't be used on a full frame 35mm DSLR later? (ok, you may think Olympus is capable of producing such a lens and sell at lower than competition ....may be $300-$400 since it's smaller glass with the 4/3 system)

So it could be marketing reason.

Every system has its advantages and one of 4/3 system's advantages is not worry as much about not getting enough DOF and is therefore more suitable than other system for certain type of photographers/photography.

 

[drakon09]

Or why olympus did not have a 50mm 1.4 lens.... but the 50mm f2 is not too bad... but for people like me who never takes macro, I am paying more for a function which I never use and furthermore it doesn't come with a focus limiter so it makes the AF super slow if it decides to hunt.

Ah, and for every one of you, there's me - shoots insects, not people. :bsmilie:

 

[microcosm]

Ah, and for every one of you, there's me - shoots insects, not people. :bsmilie:

Oh yes... you...

 

[schon]

Or why olympus did not have a 50mm 1.4 lens.... but the 50mm f2 is not too bad... but for people like me who never takes macro, I am paying more for a function which I never use and furthermore it doesn't come with a focus limiter so it makes the AF super slow if it decides to hunt.

ah... it'll be brilliant if olympus comes up with a focus limiter for the 50 f2, since it can be implemented by firmware. perhaps once the lens is mounted, an extra option under the AF menu allows u to choose to focus from .2m ~ 1m or 1m ~ infinity. or to make things better, make them user adjustable.

shouldn't this be what an all-digital system should be like?

 

[drakon09]

Oh yes... you...

And not forgetting NatureTTL...

 

[microcosm]

And not forgetting NatureTTL...

No no... NatureTTL is "nature fashion photographer"... he pose them for the shots... ha ha ha... I still wondering how on earth he does that...

 

[halcy0n]

By the way, my position is that I do not disagree on the practical effect of an object size. As we have both pointed out, and we are in agreement, the size of the object and your choice of composition will indirectly affect the DOF. However, as you have pointed out, mathematically, the size of object does not feature on the calculation of DOF.

Once we introduce variables such as composition, as Olyflyer and Schon have demonstrated, the limitations in DOF on a 4/3 system can always be overcome.

I could say that DOF is dependent on who the photographer is and by your reasoning, it would be an accurate statement. :dunno:

You may not want to agree but facts are facts. The numbers shown are not what I make out subjectively but based on facts.

Can you tell me how you're going to get shallow DOF for a building that is 210m tall and you want to have the whole building vertically up in your picture? I'm sure you can't. To include a building this tall, you definitely have to shoot further than the hyperfocal distance regardless of your focal length and aperture.

I can easily show you how to get a shallow DOF for any very small objects. Even a compact camera can do it.

For a 1m half body shot and you use 50mm, you have no choice but to stand at about 2.8m away. If you use 100mm, you have no choice but to stand 5.6m away. If you use 25mm, you have no choice but to stand 1.4m away. If you use 200mm, you have no choice but to stand 11.2m away. You may vary the distance and focal length but the DOFs are all the same if the same F number is used for aperture.

But if it's a 10cm half body shot for a small figurine instead, you can achieve a shallow DOF. Again, those afore-mentioned principles which apply for a 1m half body shot in shooting distances and focal length also apply here. This means that there are fixed combinations of focal lengths and distances which you have no choice but to use to achieve the "half body" and their DOFs are all the same if the same F number is used. Compared to the 1m half body, the DOF is much shallower here even though the composition is the same for 1m and 10cm half body.

From the above, it is clear that it is the subject size which indirectly determines the DOF simply because subject size determines the focal length - distance combination you require for the composition. Furthermore, if you want a certain perspective, your distance will be fixed and hence, you have no choice on focal length already. This is photography 101.

Mathematically, DOF is based on distance and focal length but practically, it's actually based on subject size other than aperture. Practically, since one cannot chose the subject size (if a building is 210m tall, you can't change it and if a person is 1.8m tall, you can't change it too. You can't tell the 1.8m person to become 18cm just because you can shoot nearer and have a shallow DOF for his/her half body shots, can you? Hahahaha. Even if you vary your focal length, this is only 1 distance for your half body shot for each focal length you choose and the DOF will be the same.), one can only try to vary the DOF through aperture in practice.

Facts are facts even if you don't agree. :bsmilie:

 

[purpledino]

hey people,

i'm a newbie with an E-system kit, was just wondering, will an om 50mm f/1.8 lens mounted on a 4/3 system with an adaptor give a shallower DOF compared to a zuiko 50mm f/2?

appreciate any opinions, thanks!

 

[Blu-By-U]

How about this cheapo..Sigma 105 f2.8?