If I detest Bill for saying all of us here are in denial (that not being a river in Egypt) is that like a cricket match in the West Indies?

Mike

Bjorn,

> Why? Because exposure meters are for measuring exposure,

Actually light meters are for measuring light and calculating exposure.

> The f/stop is of interest for DOF and related calculations.

t/stops are just as important for DOF as f/stops. It's the same. The only difference is that a lens calibrated in t/stops has been marked to show exactly how much light will make it through the lens at a given aperture setting, while a lens marked with f/stops has been marked according to a calculation based on lens design that should accurately represent the amount of light making it through then lens at a given aperture.

When setting the aperture on a lens marked with t/stops, one uses the f/stop calculation on a light meter for accuracy. No additional f/stop to t/stop calculation is necessary.

Serena,

> Yes, the angle subtended by the image is the thing
> that determines the necessary CC

In my experience, there's never been a "necessary CC". A DP will set a lens stop based on the composition, lens choice, light, camera sensitivity, and how easy he wants to make if for his focus puller. Nobody ever whips out their "circle of confusion" calculator and a measuring tape and sets a stop based on that. The 1st AC will use (for example) the ASC manual to determine how large his DOF field is so he knows how critical focus must be for a shot.

But in the end, one tries to keep the important stuff in focus and the not so important stuff soft because it looks good and helps sell whatever the measage is because the in focusses the audience's attention on the sharp part of the image.

For those who think that the DOF isn't a current interest, take a look at "Ratatouille" where Disney/Pixar spent a lot of money to add that effect. A lot of people -- myself included -- like the asthetic effect that also helps my brain focus on what's intended to be the focus of the scene.

BUT, I also was enamored with the Philip Bloom et al clips online, so I purchased one of the adaptors that Philip reviewed on his website. What a huge endeavor!! I worked with it for a week straight, and the workflow just was way beyond me. Likely due to the fact that I'm the camera/sound/lighting/producer/editor/etc/etc., I just couldn't work out the ability to deal with the lighting changes necessary, the lack of spontaneity due to removing the autofocus option, and quite a number of workflow modifications. If your sole job is cameraperson, perhaps. Other than that, I'm waiting for a camera that can give a shallow DOF on its own.

One thing that I do use is to take a second camera, back it up as far as possible from the subject, and then zoom in. It can actually give a pretty useful DOF in the right environment.

So does that mean you got a Letus adapter for sale for cheap? =)

- Ray
www.undergroundplanet.com

The Letus35 is a fine adapter and quite cheap even new. It gives wonderful images but all dof adapters need a full crew to carry and setup the equipment - dof adapters are not for the "one man band in the wilderness" like me or for ENG or weddings where you have to move with the action - hence my interest in the bigger sensor of the EX1, but it seems consensus is that .5" is still nowhere big enough. Pity because nothing stops even the best video from looking amature than a deep dof.

QUESTION for those of you who are using the EX1. How good is the LCD for monitoring dof? Is the LCD inage representative of the final image as it looks on a big screen?

Ray,
ha ha.... I would have (actually not a Letus), but I cried like a baby to the manufacturer and they had pity on me and accepted a return.

>>>Nobody ever whips out their "circle of confusion" calculator and a measuring tape and sets a stop based on that. The 1st AC will use (for example) the ASC manual to determine how large his DOF field is so he knows how critical focus must be for a shot.<<<

Well of course not! But when you look up your DOF in the ASC they are calculated on the standard CC. Understanding of that seems to be lacking. But change the viewing situation (eg Nokia) and the tables will not be appropriate.

Pixar: how you use DOF is an artistic decision.

> "Pity because nothing stops even the best video from looking amature than a deep dof."

This is pure opinion, not fact. Shallow depth of field is simply an artificial way of drawing attention to part of the frame whilst blurring the rest. It is an effect, which in my opinion can wear itself out quickly if overused, like many other effects.

Notwithstanding this, I am looking forward to having an increased ability to occasionally use shallow dof when my EX1 arrives next week.

Amen,
but I found the comment kind of flattering. I've always considered myself a wank amateur but if I can believe that comment then I've now joined the ranks of other great amateurs such as Orson Wells and Kubrick.

As a side note, there are other ways to separate subject from background, it's called lighting! Unfortunately it takes a lot of skill that only amateurs have :)

Bob.

This topic is wandering somewhat, but I'll put in my oar for composition as the major tool to lead the eye to the matter of significance. Lighting is the companion of composition. Too often one sees poorly composed shots that lead your eye elsewhere than the bit in focus. Shallow DOF succeeds as claimed only when the other elements are in place and there are many instances where DOPs have had to overcome problems imposed by the shallow DOF typical of 35mm. Bob mentioned a couple, and many texts illustrate the problem with phone in BCU and the person waiting for the call small in the distance. Split-field diopters, small aperture (lots of light), wide angle lenses. Short focal length lenses (such as used for consumer video cameras) inherently have deep DOF, but that doesn't say "amateur video". It's the production that says that.

Some day to day practical observations.

In the springtime I like to get out and shoot a lot of wildflower stills. These are generally closeups. To my eye, lots of sharp detail in the background makes it hard (as a viewer, not as a photographer) to focus on the subject of the shot, so since I'm out in broad daylight without the means or inclination to control the light, I opt to control the depth of field, letting the background go at least a little soft.

It's a preference. Some people seem to have more tolerance for busy backgrounds. As an alternative, I could hunt down shots with better lighting, a dark or blown out background might also reduce all that extraneous detail.

In the course of work, I shoot a lot of stills of motherboards, graphics cards, things like that. In these cases I often want more DOF than I actually have. I make it work with long exposures and by composing shots in ways that work with what the lens can do.

There's just no one rule about depth of field, except maybe that the grass is always greener with the other lens (or camera if the lens is glued to it).

Rob Mack

As much as adversity is abhorent to my nature I will defend myself against the attacks on my dof statement by two such eminent and respected memebers here as B & S. My statement was made expecting my collegues here who have long know my working method to have given me credit to have "all the other things right" and I have made it quite clear I am a lone guy in the wilderness / outback working with only natural light and I can assure you that as rmack350 so rightly remarked that when trying to draw attention to a botanical detail in high desert sun shalow dof is the tool of choice.

Further the desire for great deep dof in some earlier time was often an over-reaction to then not having it and when available it in no way gave any major advancement to our art. DOF is still used as a means to focus a viewers attention in nearly every scene of all good film and it is the reason nearly all the majot indie filmmakers who's budgets dictate video use dof adapters.

Wounded and still angry no one has the courage squash out a .5" sensor to 35mm (no need for more sensors - just spread them more) in a cheap video camera.

Although some of your remarks are quite wrong, very serious movies have been made by very serious people who expended huge somes of money to get the greatest possible DOF and that's quite recently. in your specific case it's actually quite irrelevant, you have zero control over whatever is in front of the camera so the argument is just meaningless. You could just as easily be asking for a greater DOF and face as many difficulties, or faster lenses. I'd hazard a guess for what you're shooting you'd love faster lenses, and ones with gyro stabilisation.

Expect to see the answer to your prayers from an unexpected quarter, possibly someone like Nikon. I doubt it'll be entirely cheap, a 35mm sized sensor is always going to be expensive reagrdless of the resolution. A large part of the cost of chips comes from the very die size itself.

As I mentioned before, possibly the Z7 will be a better choice for you than the EX1, with that camera a simple relay lens into the GG would give you a more compact camera and I'd imagine deliver a better image as well and eliminate the issue of keeping the camera focused on the GG.

Do not expect solutions to your problem that'll stand upto the hard knocks of shooting in the wilds to come cheaply. There's probably no better example of how difficult it is to achieve than the fate of the first 100 RedOne cameras. They're being replaced as the lens mount was not upto the task.

If it's any help to you in your adventures there's some quite cheap 2nd hand optics coming out of Russia these days in PL mount, keep an eye on eBay. The guy selling these lenses sounds as dodgy as all heck but I've been reliably told he does deliver. He recently had a fast zoom that went out to 300mm for under $2K. It did look pretty dang heavy though.

Bob.

Mike, searching through this thread I can't identify which of your statements have been attacked, by anyone. Your simple and sound question lead into the general matter of DOF. Your question was almost immediately answered as 1/2 inch is better than 1/3 which is better than 1/4, but you'll still need your Letus to get the shallow DOF you want. The discussion of what is important in determining DOF had nothing to do with your approach to shooting in the desert. It had a lot to do with many shooters in other discussion groups mistakingly identifying particular fashions as indications of "professionalism". In shooting flowers, small critters, etc in the desert a shallow DOF is a powerful tool for isolating the subject. But how you do it, how you put it together is where the professional label attaches.
If you can shoot with longer focal lengths, the EX1 has quite shallow DOF. But you will have to look at that yourself.

Serena: When you say "with longer focal lengths, the EX1 has quite shallow DOF" are you saying more shallow than the FX1's we both have? I shoot the FX1 as long as possible in these situations but its seldom enough.

What is bob hinting at from Nikon? This has aroused some curiosity?

Mike

I haven't done a side by side comparison, but if you give me some parameters I'll run a test. Size of object, what DOF you need. In playing around I've noticed that it's easy, at longer focal lengths, to throw the background well out of focus.

[b]"What is bob hinting at from Nikon? This has aroused some curiosity?"[b]

I attended a 2 day conference on tapeless acquisition, during a panel discussion it was agreed that we could see new players from the left of field such as Nikon. DSCs are getting faster at shooting bursts of frames. Nikon have much of the work already done to build a digital cinema camera with a full 35mm sensor.

Two things to keep in mind:

1) Don't expect to see it this decade.
2) Start saving now.

There's big engineering challenges going from a few fps to 24 fps and beyond. Power consumption and heat are the big one. Red continue to have issues, even JJ admits it's way harder than he thought it would ever be. Silicon Imaging had a working camera last Xmas, sort of, it worked wonderfully but was a 'frankenstein' camera. We might finally get one by this Xmas and they've got P+S doing a lot of the work so these guys aren't wet behind the ears.

It'd really, really help if we knew what you're trying to do. Clearly you're not shooting set pieces in a studio however shooting "nature" is a very broad brush. Are we talking elephants at 10 feet or dung beetles at 100 feet here???

I've never shot anything like this but I understand a few of the issues, at long focal lengths there are many problems, one being depth compression (probably the wrong term but it'll do for now), the image looks flattened and the eye cannot judge depth.

Also to state the obvious animals stay alive by not standing out in their habitat, this I learned the hard way years ago trying to hunt, don't worry the wildlife won.

So for what you're trying to do you face a number of challenges and I gather you don't have megadollars to spend either. So tell us your typical shooting scenario and if and when it stops raining down here I'll go bang some stakes in the ground and shoot a few frames with the EX1 for you and you can judge for yourself if it'll do what you want. In the end theres a whole heap of variables between what you want to achieve and what you'll endup with and just DOF calcs or charts are only part of the puzzle.

One issue I have noticed with long lenses has nothing to do with optics at all. The air acts like a mist filter, the colors wash out, resolution drops, you get image shifts due to diffraction from heat etc. So in the end maybe, just maybe there is no solution to your problem. I know some of the best wildlife shots can take years to get and it's not just problems with the talent. They can do their thing, you can be there, the camera does it's thing but the atmosphere on the day ruins the shot. So you come back next year, and the year after..

So tell us the details, one of us will do our best to help you out.
What I'd like to know is:

Distance to subject, distance from subject to background, size of subject. One other issue is that animals tend to stand close to a background if there is one. If your subject is 100M away and only 2M from the background I doubt you'll get any selective focus at all even with a 35mm camera. The EX1 lens goes from 31.4 mm to 429mm at 35mm equivalent and the maximum relative aperture is 1:1.9 Take note though, you do not get F1.9 at 429mm! I don't know just how much you loose but 2 stops would not be a bad guess. Cine zooms (the good ones) don't 'ramp' as you zoom, that's one of the reasons why they cost way more than a stills lens.

Anyway give is some clues to work with, who knows what one of us might come up with.

Bob.

Bob; your are a scholar and a gentleman! I'm in London now and flying back to LA in the morning so I'll folow up your kind offer when I get home.
Cherrs,
Mike

> Why? Because exposure meters are for measuring exposure,

I guess I stand corrected.

Exposure meters don't measure exposure, because exposure can only be assessed in a lab by measuring the length of time the shutter is open and the amount of light transmitted by the lens at a given f/stop.

They measure light and indicate the amount of light by suggesting an "f/stop" to use for a certain frame rate and shutter angle in the case of film, or shutter speed in the case of video-based formats.

The "f/stop" indicated by the exposure meter is really the T-stop. Only the T-stop directly correlates to exposure, while...

> The f/stop is of interest for DOF and related calculations.

t/stops are just as important for DOF as f/stops. It's the same.

No, they're not.

The T-stop has no direct correlation with DOF. You can have one lens at T/2.2 have exactly the same DOF as another lens at T2.0.

The f/stop has a mathematical direct correlation with DOF.

You cannot derive DOF directly from the T-stop, you have to first calculate the f/stop and plug that into the DOF formula.

The only difference is that a lens calibrated in t/stops has been marked to show exactly how much light will make it through the lens at a given aperture setting, while a lens marked with f/stops has been marked according to a calculation based on lens design that should accurately represent the amount of light making it through then lens at a given aperture.

As I have stated before:

T-stops indicate Transmission of light, i.e. what is left to provide the exposure.

F/stops indicate the relative size of the iris (a lazy definition would be "the focal length of the lens divided by the diameter of the iris").

When setting the aperture on a lens marked with t/stops, one uses the f/stop calculation on a light meter for accuracy. No additional f/stop to t/stop calculation is necessary.

That is correct for amateurs and lower level professional productions, except they don't use f/stops "for accuracy" but "for convenience at the expense of accuracy."

In higher level professional productions, lenses are marked with T-stops for exposure settings, because even 1/3 stop or 1/2 stop can make a big difference, of course especially so when matching different lenses.

Useful article here:
http://en.wikipedia.org/wiki/F-number

I've know the difference between F and T stops for a very long time, had that drummed into me a by photog way, way back.
Where I loose it is working out what is "1 Stop". The article above does clear that up, I suspect many of us throw around things like "1 stop" more but what is one stop more, f1.4 to f 2.0 is one stop and so is f 2.8 to f4.0.
However f1.2 to f1.4 is 1/2 stop even though a lens might have "stops" with those numbers on them.

At least the audio guys got their act together with dB!

Bob.

Edit: Changed f1.2 to f1.4, bad mistake.

f1.2 to f 2.0 is one stop

Umm, f/1.4 to f/2 is one stop.

..and I'll stop at that. :O)