[CSoars]

Now in the quest for achieving out of focus back(and fore)grounds, we know a few things affect this; namely close working distance, focal length, and fast apertures.

Now there's a kind of shot I'm itching to try that is essentially a full body portrait where only the subject is in a narrow sliver focus. It appears that this is achieved by using a 200-300mm lens, but to fit the person in the frame.


from Neil van Niekerk's photoblog.


This was with Canon's 200mm f/2 L IS.
I presume the longer the focal length, the slower the aperture can be because of the compressing effect. Would a 300mm f/2.8 (100mm longer, 1 stop slower) provide a similar effect if framed the same way? Or would increasing the working distance also increase the DOF surrounding the subject? How would a 200mm f/2.8 or 300mm f/4 compare?

This could be a really interesting effect for portraits and location shooting for bands etc, especially if you have enough room to place them in front of an interesting background, then use the telephoto to 'pull' it in close but still OOF. Adding strobes to light the subject, background or both could be interesting too.

[Photomaximum]

It all depends on the subject to lens distance, how much of the subject fills the frame, the depth of field wanted, the bokeh character, the price you are willing to pay for the lens, and how well a fast lens performs near wide open. In short there are a ton of variables here.

I have tried a lot of options in this arena. My most recent favorite is the rare Minolta Rokkor 58/1.2 lens adapted to a FF camera shot at f/2 which yields simply incredible results...

[BBear]

Would a 300mm f/2.8 (100mm longer, 1 stop slower) provide a similar effect if framed the same way? Or would increasing the working distance also increase the DOF surrounding the subject? How would a 200mm f/2.8 or 300mm f/4 compare?

It's a bit too late for me to check the tables, but you have a good question here... comparing for instance a 200mm f/2 X 300 f/2.8.

Plugging that in on a DOF table will give you the values. I'd inclined to say the 300 f/2.8 will have a thinner DOF.


Regarding the working distance, the 300mm will required even more distance, so depending on the background relationship, i guess it'd... huh.... i need the tables before i claim something wrong here, so i'll be quiet!

[Venturi]

It's late, but this is actually something I'm in the process of digesting (just finished reading "The Camera" and started on "The Negative")...

Assuming we're framing the same print:

- The Canon had either a 1.43, 1.73 or 2.26 ft DOF, depending on the model, with the 200 @ f/2.0. Given that lens goes for $5500 I'll guess he's got the 1Ds MkIII so 2.26 ft. (I assumed 50ft to subject for shot)

Here's how our long primes stack up with the K10/K20:

DA*200mm, F/2.8 @ 50ft == 2.13ft DOF
FA*300mm, F/2.8 @ 75ft == 2.13ft DOF
DA*300mm, F/4.0 @ 75ft == 3.01ft DOF
DA*300mm, F/4.0 @ 63.25ft == 2.13ft DOF

source: Online Depth of Field Calculator

[CSoars]

It's late, but this is actually something I'm in the process of digesting (just finished reading "The Camera" and started on "The Negative")...

Assuming we're framing the same print:

- The Canon had either a 1.43, 1.73 or 2.26 ft DOF, depending on the model, with the 200 @ f/2.0. Given that lens goes for $5500 I'll guess he's got the 1Ds MkIII so 2.26 ft. (I assumed 50ft to subject for shot)

Here's how our long primes stack up with the K10/K20:

DA*200mm, F/2.8 @ 50ft == 2.13ft DOF
FA*300mm, F/2.8 @ 75ft == 2.13ft DOF
DA*300mm, F/4.0 @ 75ft == 3.01ft DOF
DA*300mm, F/4.0 @ 63.25ft == 2.13ft DOF

source: Online Depth of Field Calculator

Haha very informative, I've not used anything above 100mm for any real period so I've little notion of what working distances are needed to frame what.

So are you implying that the Mk III DS is 2.25 feet @ 50 ft and f/2, while the DA* 200 @ 50 ft. and f/2.8 has a narrower DOF, despite the same distance and smaller aperture? I'd have thought the larger sensor would narrow it down due to the reduced working distance to maintain a similar field of view; the K10D with the DA* 200 would have less OOF due to the extra stop and increased distance.... hrmm.

[Venturi]

I'm implying nothing, that's just what their handy dandy javascript told me. LOL

[roentarre]

I could recall a thread by Joe Mama from DPR on top of my head that 300mm f2.8 renders more throw of background blurr comparing to 50 f1.2 given the subject to camera distance is the same (???? How is this a controlled variable?). He also made a claim that 135mm f2 has a thinner depth of field comparing to 85mm f1.2 as well etc. I remember that there is some sort of optical forumula that quite a few people were obsessed about, debating for ages that did not make any sense to me.

Nevertheless, it is not about how thin the depth of field can be for most of photographers who care about bokeh. This is to do with bokeh "quality" and "highlight performance"

That canon 200mm f2 IS L bokeh is terrible (typical of of canon L lenses) but it takes on flare and highlight not too badly. I had been checking around for most of wide open shots of 200mm f2 most being quite dissapointing according to my personal taste. One can see that the bokeh are harsh with sharpened edges.

[CSoars]

I'm pretty intrigued/enamoured of that A* 300mm f/2.8 you managed to find, then purchase, then use, James. Ever use it outside the scope of critters & bugs?

[Miserere]

Pardon me if I seem curt and conceited, but I'm getting tired of posting this time and again on different posts all over the forum whenever this theme comes up:

Given a fixed subject size within the frame, the Depth of Field (DoF) depends exclusively on the aperture being used.

So, taking the picture of the girl on the tracks as an example: Whatever lens you use to take that picture, 28mm, 50mm, 200mm or 300mm, as long as the girl is the same size in each photo, the DoF will be exactly the same as long as each picture is shot at f/2. What will change is the amount of background included in the frame; the wider the focal length, the more surroundings you will capture. Longer focal lengths can appear to have a smaller DoF simply because they include less background in the frame; this is due to changing perspective, and is one of the reasons we have lenses of varying focal lengths. All this is true for a given sensor size, so don't compare between full-frame, APS-C and 4/3.

If you don't believe me, plug the numbers into a DoF calculator. Use a constant aperture (say f/2.8), and the following pairs of focal lengths (in mm) and distances-to-subject (in meters) that will ensure your subject appears the same size in every frame:

25mm + 5m
50mm + 10m
100mm + 20m
200mm + 40m
300mm + 60m

Please, pass this message along. I'm getting tired of having to write it out again and again.

[CSoars]

Pardon me if I seem curt and conceited, but I'm getting tired of posting this time and again on different posts all over the forum whenever this theme comes up:

Given a fixed subject size within the frame, the Depth of Field (DoF) depends exclusively on the aperture being used.


Please, pass this message along. I'm getting tired of having to write it out again and again.

Guess I was fishing for examples, or trying to figure out how pronounced the effect would be between apertures, because narrower FOV's require more working distance, and in most cases, the longer the lens, the slower the working aperture. Therefore absolute DOF was secondary to how a 'more compressed' FOV due to a longer lens works with deeper depth of field due to a slower aperture.

Primary interest was the appearance of the back and foreground, and their relationship to the subject to keep them as OOF as possible, because bokeh has a 'zone of transition' so to speak.

I understand it's frustrating and should have worded the original post a bit better.

[Miserere]

CSoars, my reply wasn't aimed at you, but at the forum community at large. My frustration also I apologise if you felt singled out, that wasn't my intent.

As you say, sometimes a narrower FoV can compensate for a deeper DoF, so you want to know whether 300mm at f/5.6 will suit your needs better (or equally) than 200mm f/2.8, even thought your DoF is 2 stops deeper. Seeing as the price difference between the two lenses will be large ($900?), this is certainly a worth-while question.

[FHPhotographer]

Ah, memories of Creedance and "...barefoot girls dancin' in the moonlight."
Brian (FHPhotog)

[Venturi]

While the subject matter isn't necessarily rocket surgery it is a bit challenging at first to wrap your brain around. For most, the subject of bending light isn't terribly intuitive and when you introduce compound lenses and varying film/sensor sizes it gets very muddy in short order.

After months of wrestling with the subject(s) via various sources I finally (I think) got my brain wrapped around most of it after finishing up with Ansel Adams' Book 1 "The Camera"...

For any given photographic subject from a fixed viewing position and constant aperture:

+ The perspective remains constant regardless of focal length and film/sensor size. Perspective being defined as the relative size and position of each object in proportion to each other within the frame of the shot. Perspective only changes by changing your viewing position with respect to the subject - be it nearer, farther, higher, lower, to the left or to the right.

+ The field of view (how many degrees from zero, or straight ahead) captured will vary with changes in focal length and film/sensor size. If the film/sensor size remains constant, the field of view will decrease as the focal length increases. If the focal length remains constant, the field of view will increase as the film/sensor size increases.

+ The depth of field will vary with changes in focal length and film/sensor size. With constant film/sensor size the depth of field will decrease as the focal length increases. With constant focal length the depth of field will increase as the film/sensor size increases.

Where's the teacher, and do I get a gold star or a dunce cap?

[BBear]

and distances-to-subject (in meters) that will ensure your subject appears the same size in every frame:

25mm + 5m
50mm + 10m
100mm + 20m
200mm + 40m
300mm + 60m

Right on Miserere,


Could you just clarify how you figure out the additional camera-to-subject distance?

Are you just doing a linear ratio here? Hmm... it seems like it... so this is a really stupid question but i'll post it anyways.. just to confirm.


Thanks

BB

[Miserere]

+ With constant focal length the depth of field will increase as the film/sensor size increases.

This is the only one that's incorrect. The DoF becomes narrower (decreases) as the sensor size increases. This is why digital P&S cameras have such huge DoF, because they use tiny CCDs. It's also why Ansel routinely shot landscapes at f/64 on his 8x10 camera.

Other than that, the rest is all good and I will recommend that the teacher give you a gold star