MF- More shallower depth of field.

gregory_king1 · January 19, 2011

All that arguing about semantics, and you still didn't get to the good stuff. Bummer. :-)

You find it silly to put a common standard on DOF. I don't. I get your point. I need no further explanation.

You'd apparently rather we say "Medium format systems provide a much narrower region of acceptable sharpness for similar shooting conditions , when printed under proper printing conditions, and viewed under proper viewing conditions, by the same viewer on the same day in the same mood.

I'd prefer to just say "Medium fomat systems provide narrower DOF".

Six of one, a quarter dozen multiplied by the cube root of 64 divided by the hypotenuse of a right triangle divided by a leg squared of the other.

I think it's much more useful to define it using a common set of standards, just like nearly everything else in human society. Stairs, railings and counters are built to standards. Heck, even the definition of 20/20 vision is empirically based. Does that make it less useful?

I suppose you'd rather we had no scales on camera lenses, or online DOF calculators, because that would be too...simplifying? There are just too many variables, so we might as well avoid the issue altogether?

I have to go now. I plan to speed home. If I get stopped by a cop, I'll just tell him that the speed ratings they put on the road don't apply to me, since obviously they weren't aware of the capabilities of my car and my incredible driving skill. ;)

And to drag us back kicking and screaming to the OP...Mario Andretti will still be a better driver than me, no matter what measurement you use.

jose_angel · January 19, 2011

I cannot understand how I came to that my latest post. (My knowledge of english is very limited, I actually sweat blood when I want to write comprehension concepts). My excuses.

Q.G. I`m pleased reading your contributions. Very interesting, as usual. Thanks a lot. If you decide to write about the "tiny format" issue, I`ll be here to read it.

gregory_king1 · January 19, 2011

Don't worry, Jose...your English is better than most native speakers. ;-)

And it's obvious you know your stuff. As does Q.G. We're like three overeducated nerds discussing minutiae, so much so that we scared the original poster off. ;-)

So I humbly suggest we suggest a truce and end the bickering over DOF, viewing distance and resolution, because I'm pretty sure we all think the same thing, regardless of how we express it.

Now, if we can put the tiny sensor issue to bed, we can go off fat, dumb and happy and take some photos. And maybe I'll send back the MFDB I just bought, since Q.G will show me how to take the same shallow-DOF photos with my P&S. ;-)

dave_redmann · January 20, 2011

[T]he standard definition of DOF is calculated irrespective of print size.

Whose standard is that? That's about like the apocryphal story of a bill being introduced in the Louisiana Legislature, by a math-challenged legislator, to officially establish the constant Pi to be exactly 3--no more of this 3.14159 stuff to remember. It just ain't so! There are shorthands that assume a certain print size, but that does not remotely make depth of field independent of print size.

Tonight I'm not about to wade through all the math in that Wikipedia entry. Suffice it to say that, as much as I generally value Wikipedia, refer to it all the time, and have both originated and edited articles, sometimes it contains stuff that is really out there, or just wrong. Or maybe you are misinterpreting what's there. If you care to be more specific in that huge entry, I'll take a look. But it does say, "For a given format size, at moderate subject distances, DOF is approximately determined by the subject magnification and the lens f-number." Now for a given format, magnifaction is print size!

By the way, Q.G., my depth of field calculator does account for print size (albeit the input is for magnification). It also lets you choose your own print circle of confusion, although it defaults to 0.180 mm and recommends a range of 0.125 - 0.250 mm (roughly 1/200-inch to 1/100-inch, values long ago blessed by St. Ansel). It's in an Excel spreadsheet. E-mail me if you want it.

dave_redmann · January 20, 2011

I stand by my statement the DOF has nothing to do with print size. Rather, print size has everything to do with your perception of the DOF.

John, in a word: no, no, no, no (VBG!). The whole concept of depth of field by its very nature and by definition is based on our perception. In the truth of physics and optics, only one infinitessimally-thin plane is truly in focus and therefore truly sharp. The rest is unsharp, some more so and some less. Depth of field is our expression, our opinion (well, for standard references, somebody's opinion, at least) about how much unsharpness is inconsequential enough that it still looks reasonably sharp. And that depends on your personal standards and taste, but there are some common ranges, and we can calculate the values for whatever standards you want to apply.

Jose may have hit on some of the confusion. Yes, the negative or transparency or digital file has whatever data it has. And as he says, in terms of resolution, it's fixed. But although resolution and sharpness are related, they are not the same thing.

gregory_king1 · January 20, 2011

Dave,

I'm not sure whose definition it is, but you better get on Google ASAP and get started correcting the ignorant masses. Of the entire first page of hits, I found only one that asked for print size. The rest shockingly left it out.

So it seems a lot of people have become comfortable with a "standard". Perhaps it's the same people who make the DOF scales for camera lenses...who knows? Must be...since one of the "sloppier" websites offered up this explanation:

It should be noted that an 8x10 inch print viewed at arm's length has long been considered the standard on which most lens manufacturers base their lens' depth of field guidemarks.

</blockquote>

By the way, since you're being so picky. you forgot "viewing distance". It's not just print size, remember? Gotta factor in viewing distance too...lest we confuse anyone. :-)

q.g._de_bakker · January 20, 2011

Gregory, Shrugging this off as about semantics is kind of silly. ;-) Semantics - to play a semantics game - is about what the words we use mean, what words we pick to express some thing. So even if it were about semantics, it should have made you think about the matter itself. About the things you are talking about using the words you have. Which you indeed should do (as i have pointed out a couple of times already). So yes. Dave, I believe (can't read it while on this page - can't leave this page while writing this) i acknowledged that some calculators do offer to set print sizes and such. Thing that remains is that, though it would appear very usefull, it is not. Not, simply because those viewing distances, print sizes, and what not, are never the same. It's nice theory, that only in very rare circumstances happens to coincide with practice too. But you do acknowledge the (at least) fuzzy nature of DoF, so i will not hold that against you. ;-)

david_smith35 · January 20, 2011

I'll bet Steve Johnson's got a headache after reading all this - I know I have.

ondebanks · January 20, 2011

maybe I'll send back the MFDB I just bought, since Q.G will show me how to take the same shallow-DOF photos with my P&S. ;-)

</blockquote>

Hey Gregory, so you just got a MFDB? Congrats! Which one? Is this replacing the tethered-only one you had before?

(Notice how I skilfully avoided even mentioning D**...you know, that word)

nee_sung · January 20, 2011

I suppose in the old days, when all photos are printed, print size is all important. Nowadays the confusion probably arises because the vast majority of photos seem to be viewed on screen, one type or another. The size of the screen then becomes important. But I don't think any DOF scale published has been based on an (assumed) screen size.

jose_angel · January 20, 2011

Gregory, I appreciate your kindness... I should not enter into the mood without a good pair of boots.

BTW, I checked DoF marks in a few 35mm and 6x6 lenses time ago. My conclusion was that they are different because they take format into account... MF lenses have a lower magnification demand, hence the CoC value can be higher. A given focal lenght will have larger DoF on the smaller format. This scales tallied in 8x10" (10x10") prints from both my 35mm and 6x6 cameras.

Dave, my point was in that direction... probably driven to nowhere place. A given print size has the resolution it has, no more no less. The right viewing distance has to be set accordingly. Well, you can set the viewing distance as a constant, and modify the print magnifcation to get a different resolution... sincerely I don`t know where this drives.

I actually don`t know how to thread the puzzle. Well, I`m struggling my head with the limiting factors... but I don`t want to mess up again.

desmond_kidman · January 20, 2011

I'd like to try to be more clear here by defining what exactly is being talked about.

1. The same "effective" focal length should be used on the smaller and larger format cameras. For example, if we use a 50mm (normal lens) on a 35mm camera then we should use a 80mm (normal len) on a 6 x 6.

2. Each camera must be at the same location.

3. Same f-stop on each lens.

4. Enlarge each to the exact same final size print.

If you do the above you will see that the smaller format image has less blur when you look at parts of the image that

are beyond and before the focal point. No arguements, please, just do it and you will see.

Now, with a digital camera you can simulate this and see immediately. Take a shot with a 50 mm lens and a 200

lens from the exact same spot. Bring them up on your computer and get them onto the screen at the same time

(called tiling in photoshop). Adjust the images sizes to make details on each the exact same size.

We are simulating the same "print size".We simply want details in each image to be

the exact same size. And here you will see it: details beyond and before the focus point with the 200mm lens will

be totally blurred while the exact same details on the 50mm image, exactly the same size on your screen, will be

easily discernable. I just did this 10 minutes ago, on a Canon 1Ds3, with a 50mm and 200mm lens, and

the difference in blur, at the exact same image size on the screen, looking at points closer

and further from the focal point is huge, as always.

Those of use who have shot 35mm, 2 1/4, 4 x 5, and 8 x 10, and enlarge to the SAME FINAL PRINT SIZE, have

been living with this for years.

Let me repeat myself: DO THE TEST.

desmond_kidman · January 20, 2011

To bring this back to the real world, yes, taken from the same distance a portrait on the "corresponding" length (i.e. comparing normal on a MF to normal on a 35mm) lens and at the same aperture will have more foreground and background blur when printed at the same final image size. And this is indeed the bane of small sensor digital cameras. You need a very large aperture to get the same blur you would on a larger sensor digital camera. An image at f2.8 on a small digital sensor has very little blur compared to the same image at the same distance with the same f-stop and final print size as a shot taken with a "full frame" (24 x 36) DSLR.

john_c16 · January 20, 2011

Dave - I see your point. After rereading my post, I'm not really sure what I intended to say because it didn't quite make sense. I'd use the excuse that it was late, but it was the middle of the day so I guess I'm out now. My brain hurts.

gregory_king1 · January 20, 2011

Hey Gregory, so you just got a MFDB? Congrats! Which one? Is this replacing the tethered-only one you had before?

(Notice how I skilfully avoided even mentioning D**...you know, that word)

</blockquote>

Ray,

Yep, I stumbled on a 22wi. We'll see if it'll still have to be tethered or not. Supposedly it can be self-powered and "self-tethered" to an Ipaq PDA. Whether or not this will work, or whether it'll shoot untethered and unviewed (stored directly to digital magazine without the Ipaq) remains to be seen.

Couldn't pass up that 36x48 sensor...and all the shallow DOF it provides. ;)

nee_sung · January 20, 2011

It is a well known fact that DoF is a function of the focal length. Therefore a normal lens for MF (let's say 80mm) has less DoF than the normal lens for a 135 format (50mm). That's the main reason why so many people want full frame digital: the DoF of smaller digital cameras are just too great to isolate the foreground.

Is that what all these posts are about?

gregory_king1 · January 20, 2011

Oh no...you didn't. Nee, please say you didn't say that. All hell will break loose. ;-)

AlanKlein · January 20, 2011

Wow. I shouldn't have come back. Now we're up to 10 commentators with 14 opinions!!

If I may pull this thing back on track. The OP stated that MF has a narrower DOF. Well, we've gone off the path to discuss what is DOF, what is COC, how it can be measured, the size of prints, looking distance to the print, etc. Isn't that all beside the point? Let us assume whatever the standard you wish to make is the true standard regarding those things. With all these things remaining equal, does MF have less DOF, more or equal DOF to let's say 35mm full format?????

Let's keep it simple.

q.g._de_bakker · January 21, 2011

Nah... To put this back on track, i'll repeat that DoF is a mythical thing. Everybody holds their own set of beliefs about what it is and how it behaves. Most, if not all, of them are false. People are seeing blind, believing what they want to belief about DoF even when they can see it's not so. But i'm sure you will not agree. So just consider this (has been said a couple of times before): DoF 'values' (i shudder when i write that - the inanity of the very idea!), in whatever understanding of DoF you might adhere to, are only 'valid' (ha!) in a very small set of circumstances. Circumstances that are never met in real life. So why do you bother?

jens_g.r._benthien · January 21, 2011

I guess you all have missed the point.

Assuming identical focal lengths, the OP is wrong, assuming identical angles of view / fields of view, the OP is correct:

A 90mm lens on a 35mm system and a 6x9 system physically feature the same shallow DOF. However, a 90mm on a 35mm system means you are compressing the visual appearance of the scene - it is a telephoto lens.

With 6x9 and a 90mm the field of view equals a 50mm on a 35mm system - but, because of the 90mm, features a shallower DOF than a 50mm.

So if we talk about identical viewing angles / field of view, the MF or LF lenses deliver a very 'thin' DOF.

In addition the MF film delivers a significantly higher resolution, that means transitions are smoother and edges are sharper. This adds to the effect of the thin DOF **if** you shoot with an open aperture.

Everything else is just hot air and gossip.

desmond_kidman · January 21, 2011

Why has nobody else written that they have gone and done the test as I have?

For those who use the word "opinion", this is not opinion, it is fact:

Even with the greater enlargement factor from 35mm when making the identical print size as a medium format, if the shooting position is the same and the field of view is the same (meaning using the longer lens on the mf camera) the out of focus areas of the 35mm print will be SHARPER than the same areas of the mf camera print.

Note the key words: I did not use c of c, or depth of field, or calculation, or any other parameter that is based on convention. Just do the test, print the prints at the same size, and you will see. If you are one of the guys, who seem to be in the majority, who hold the opposite view, you will be surprised and will have to change your view.

I think that none of those holding the opposite view have ever shot 8 x 10 as well as 35mm. If you had then you would have been slapped in the face by a 8 x 10 contact print shot at f4 that has serious blur as soon as you get away from the plane of focus.

Do the test!

jens_g.r._benthien · January 21, 2011

Desmond, you are right, but it appears to me that nobody else is willing to understand :-(

I tried to simplify the explanation, but I guess I failed

What most people don't understand is the FOV or field of view... hard to explain, so your recommendation to perform a test is really the best to experience this effect.

On the other hand: Don't try to teach a dog to sing, it annoys the dog and wastes your time :-))

gregory_king1 · January 21, 2011

Circumstances that are never met in real life.So why do you bother?

</blockquote>

Q.G...that is the most nihilistic explanation I've ever heard. Let me see if I can top it. ;-)

Reality is false, nothing is real. Don't bother taking photos in the first place... they are just bastardized representations of microseconds in time, incorrect in all aspects and fleetingly ephemeral. Two-dimensional surrogates which do no justice to an entire dimension of human existence.

Eschew photography and live in the moment.

I guess asking for the "tiny format DOF is the same as large format" is futile, eh? ;-)

desmond_kidman · January 21, 2011

Jens, it shocks me how folks ignore truth or fact because it is too much work for them to actually learn, or do an experiment. Plus, it might challenge their "guru status" (thinking of one of the "experts" on this forum who NEEDS to be the expert) to admit they might have made a mistake.

So, I have 2 shots from the identical spot, the first a 50mm, the second a higher quality 200mm, and it is so easy to see that the 50mm, despite being poorer quality and having to be enlarged much more (4x), still has much less blur in the out of focus areas. I am trying to post them here. They are of a map. Try to read the out of focus names on the map and it's immediately obvious that one lens renders much more readable names, despite the fact it is the lower quality lens and the image had to be enlarged 4x the amount of the image made with the 50mm lens.

Both shots are at the same aperture.

Again, notice I am not using terms like c of c, depth of field calculations, etc. Just compare the out of focus areas. The 50mm retains greater detail when you examine areas that are out of the image plane.

nee_sung · January 21, 2011

Desmond: you are of course correct. I don't need to do the test. I shoot 135, MF and LF and I experience it all the time.

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MF- More shallower depth of field.

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