GH1 DOF Vs HMC-150/HPX170

[studio1972]

Not sure if anybody has already done this, but I was interested in what the GH1 might give me in terms of DOF compared to my HMC151. These calculations were done with the stock GH1 lens which is designed with video in mind. Obviously the results would be different with prime lenses etc.

Distance to subject = 5m
35mm equivelant focal length = 100mm
Aperture fully open in both cases

HMC = 2.45m at f/2 13.8mm
GH1 = 1.83m at f/5.6 50mm

Distance to subject = 5m
35mm equivelant focal length = 200mm
Aperture fully open in both cases

HMC = 0.7m at f/2.4 27.6mm
GH1 = 0.44m at f/5.6 100mm

I used this online calculator:

http://www.cambridgeincolour.com/tutorials/DOF-calculator.htm

It seems like the GH1 is capable of shallower DOF, but not so much as you might expect given that the sensor is 4 times as wide. I haven't done the maths, but I would imagine that an EX1 might come out with similar figures to the GH1 as it has a better lens than the HMC and a slightly larger sensor.

 

[Martti Ekstrand]

The fall-off of focus outside the DOF is greater with a bigger sensor than these numbers indicate. Which shows in the image.

 

[studio1972]

The fall-off of focus outside the DOF is greater with a bigger sensor than these numbers indicate. Which shows in the image.

Ok. I've just done the same calcs for the EX1, and it comes out at 1.68m and 0.41m respectively. This means it has slightly shallower DOF than the GH1.

Regarding your point about the larger sensor, I believe that this is counteracted by the narrow aperture of the GH1 lens. Of course, you can get other lenses for the camera.

Regards

Stuart

 

[Tim Joy]

You can get razor thin DOF with the GH1 and the right lens, so the question is- How much do you want?
Compared to 1/3" cameras, you have much more control, and you can get shallow DOF in almost any shot with a reasonably fast lens above about 35mm, or shooting CU with wide lenses.

 

[studio1972]

I was talking about the stock lens. Obviously with another lens the situation would be different. What I am saying is that if you intend to use the stock lens (which has a reasonable zoom range etc.) then you are going to get DOF in the same ball park as an EX1 and not much better than a 1/3 camera. The GH1 is much cheaper than these, so I'm not trying to slate it, I was just a bit surprised when I worked it out, and thought people might be interested as it seems most people seem to expect shallower DOF on the 4/3 camera.

 

[Ben_B]

The nice thing about a camera like the GH1 is that you can get shallow DOF in almost any situation if you need it. The HPX170 can get very shallow DOF if you need it, but you have to be shooting wide open, get far back, etc.

Here's some HPX170 screen grabs from a friend of mine when we were shooting around with the HPX and the GH1 that show off potential DOF of the HPX.

 

[Tim Joy]

Ahh. I see your point. Yes, it is close to the 1/3" cameras but just that little bit of extra shallowness is really nice sometimes.

 

[Barry_Green]

At the same aperture, the GH1 will be astoundingly shallower than the EX1 or HPX170 or HMC150. If you're going to go comparing f/2 to f/5.6, then of course you're going to end up with the results you got. But when are you going to be shooting f/2 on one camera, and in the exact same circumstances shooting f/5.6 on another camera? That's not gonna happen.

Aperture to aperture, the GH1 is going to be extremely much shallower.

 

[Ben_B]

And in the end, that's why many of us bought it.

 

[studio1972]

But when are you going to be shooting f/2 on one camera, and in the exact same circumstances shooting f/5.6 on another camera? That's not gonna happen.

Both cameras are fully open in this situation, I often have my HMC lens fully open, and I would do the same with the GH1 if I had one, seems like a perfectly reasonable comparison to me. Why would you not use the HMC at f/2.0 in a similar situation?

Surely you are not seriously arguing that you would have the same aperture in the same situation with a 1/3 camera as you would with a 4/3 camera?

Aperture to aperture, the GH1 is going to be extremely much shallower.

That's undoubtably true, but also a straw man. The EX1 has a lens with a wide zoom range at f/1.9, if such a lens could even be produced for a 4/3 sensor camera it would be enormous and would cost a fortune. The stock lens on the GH1 can go no more open then f/5.6 at the zooms I calculated.

Yes, you could use a prime lens on the GH1, but then you would have much less flexibility. An aperture to aperture comparison is really meaningless given that you would be falsely restricting the EX1/HMC to carry out this comparison.

 

[Barry_Green]

Both cameras are fully open in this situation, I often have my HMC lens fully open, and I would do the same with the GH1 if I had one, seems like a perfectly reasonable comparison to me. Why would you not use the HMC at f/2.0 in a similar situation?

Because the HMC would be overexposing the shot by two stops!

Surely you are not seriously arguing that you would have the same aperture in the same situation with a 1/3 camera as you would with a 4/3 camera?

Of course you would. Why wouldn't you? Sensor size has nothing to do with the amount of light that you want to have entering the lens. In fact, in normal circumstances I'd want the GH1's lens *more* wide open than the HMC150's whenever possible. Why? Because I prefer the GH1's look at 100 ISO. So assuming equivalent shutter speed, the HMC150's native 500 ISO would dictate a certain f-stop, and setting the GH1 to 100 ISO would mean needing about two stops' more open iris for proper exposure.

That's undoubtably true, but also a straw man.

Why on earth do you say it's a "straw man"?

The EX1 has a lens with a wide zoom range at f/1.9

The EX1 does not have a lens with a wide zoom range at f/1.9. It is only f/1.9 at the most wide-angle end. It ramps (just like the GH1 and all other lenses of similar design), it's nowhere near f/1.9 when at full tele. It just lies to you by not TELLING you that it's ramping, but it is.

Yes, you could use a prime lens on the GH1, but then you would have much less flexibility. An aperture to aperture comparison is really meaningless given that you would be falsely restricting the EX1/HMC to carry out this comparison.

How? If you assume that the GH1 is going to be able to get accurate exposure at whatever zoom setting you're at, then you're going to have to set the EX1 or HMC to the same aperture, or deeper, because both cameras are inherently faster.

Even if you set them to the same ISO, you'll need the same aperture to get proper exposure. And the GH1 will slay in DOF in that circumstance.

So the only way your comparison holds valid is if you're either a) willing to accept grossly underexposed footage on the GH1, which seems like a false argument, or b) using ND filters on the EX1/HMC.

In any case, look -- I own a GH1, and an HMC150, and an HPX170, and I don't need to go resorting to calculators to try to prove a point which is obviously and easily disprovable in simple usage. Testing trumps theory every time. Actually grab the cameras and go out and shoot some footage and you'll find out real quick, very quickly, the GH1 has extremely shallower DOF than any 1/3" camera no matter which way you slice it.

 

[studio1972]

Because the HMC would be overexposing the shot by two stops!

You could use an ND filter on the HMC, also this would surely depend on the ISO.

Of course you would. Why wouldn't you?

Here's some very obvious reasons:

1. You might want shallow DOF, and would therefore want to have the iris fully open on the HMC

2. The light level might require you to open up the iris more than 5.6

3. The 2 sensors presumably don't have identical ISO

Sensor size has nothing to do with the amount of light that you want to have entering the lens.

Yes it does, If I want shallow DOF with a 1/3 sensor I will need a wider aperture for the same angle of view.

In fact, in normal circumstances I'd want the GH1's lens *more* wide open than the HMC150's whenever possible. Why? Because I prefer the GH1's look at 100 ISO. So assuming equivalent shutter speed, the HMC150's native 500 ISO would dictate a certain f-stop, and setting the GH1 to 100 ISO would mean needing about two stops' more open iris for proper exposure.

Why on earth do you say it's a "straw man"?

Because you could simply use the built in ND filters in the HMC to reduce the amount of light without having to close the iris. It is a straw man argument because you are deliberately ignoring factors such as this.

The EX1 does not have a lens with a wide zoom range at f/1.9. It is only f/1.9 at the most wide-angle end. It ramps (just like the GH1 and all other lenses of similar design), it's nowhere near f/1.9 when at full tele. It just lies to you by not TELLING you that it's ramping, but it is.

It's still a lot wider than f/5.6 though I would imagine. Let's say it's f/2.4, that still puts the DOF only slightly wider than the GH1 stock lens.

How? If you assume that the GH1 is going to be able to get accurate exposure at whatever zoom setting you're at, then you're going to have to set the EX1 or HMC to the same aperture, or deeper, because both cameras are inherently faster.

Even if you set them to the same ISO, you'll need the same aperture to get proper exposure. And the GH1 will slay in DOF in that circumstance.

ND Filters

So the only way your comparison holds valid is if you're either a) willing to accept grossly underexposed footage on the GH1, which seems like a false argument, or b) using ND filters on the EX1/HMC.

b it is then :thumbup:

In any case, look -- I own a GH1, and an HMC150, and an HPX170, and I don't need to go resorting to calculators to try to prove a point which is obviously and easily disprovable in simple usage. Testing trumps theory every time. Actually grab the cameras and go out and shoot some footage and you'll find out real quick, very quickly, the GH1 has extremely shallower DOF than any 1/3" camera no matter which way you slice it.

Are you talking about the stock lens? If so I don't know why the laws of physics suddenly break down just because you assert it? I have just tried comparing my HMC fully open to my 450d at f/5.6 with a similar viewing angle (160mm 35mm equivalent) and the DOF looks similar to me, which stacks up with my calculations.

 

[Barry_Green]

I'm not sure why real-world experience has to take a back seat to calculators, but let me try this a different way:

The GH1 delivers shallower DOF than the 1/3" cameras.

I'm *extremely* well versed in what one can do to get the maximum performance out of a 1/3" camera in terms of shallow DOF. They do not compare.

If your mileage varies, it is only because you want it to, to prove an esoteric point.

In any practical shooting situation, you will get shallower DOF out of the GH1. And if you want to push things, putting a 50mm f/1.4 lens on a GH1 costs maybe fifty bucks and gives you phenomenally shallower DOF, and takes about 10 seconds to accomplish.

The 150 is a better video camera in all ways (except ultimate sharpness, when the GH1 is behaving at its best) but to assert that they're comparable in DOF terms simply denies the reality of actually using the products.

 

[studio1972]

I'm not sure why real-world experience has to take a back seat to calculators, but let me try this a different way:

The GH1 delivers shallower DOF than the 1/3" cameras.

I'm *extremely* well versed in what one can do to get the maximum performance out of a 1/3" camera in terms of shallow DOF. They do not compare.

If your mileage varies, it is only because you want it to, to prove an esoteric point.

In any practical shooting situation, you will get shallower DOF out of the GH1. And if you want to push things, putting a 50mm f/1.4 lens on a GH1 costs maybe fifty bucks and gives you phenomenally shallower DOF, and takes about 10 seconds to accomplish.

The 150 is a better video camera in all ways (except ultimate sharpness, when the GH1 is behaving at its best) but to assert that they're comparable in DOF terms simply denies the reality of actually using the products.

I said in my original post that I was only comparing the stock lens to the HMC. The GH1 does have shallower DOF in this scenario as per the calculations, but not by much!

Putting a f/1.4 prime lens on it changes everything, I never denied this. This is another straw man!

So are you saying that my calculations are wrong? If so, maybe you can explain why, or provide some proof in terms of images? As I said I have just compared the HMC to my 450d and the DOF is similar, with the 450d at f/5.6 as the GH1 would be. Are you saying that I'm making it up? Do I need to back this up with images for you to believe that what I have said, based on standard calculations, is true?

 

[John Caballero]

Do I need to back this up with images for you to believe that what I have said, based on standard calculations, is true?

You have to actually go get a GH1 and put it next to the HMC and shoot along. You have to prove your point in the real world, out in the field with proper samples. Then if you are right you would have proven your point with actual images from the cameras you are debating about.

 

[Barry_Green]

"only comparing the stock lens" is in itself a straw man. The first thing many of us do is pull the stock lens off! To ignore that is to tie one man's hands behind his back and then say "see, I can beat this guy up". What's the point in that?

What I'm saying is: calculations don't mean jack squat, when what you do in the real world under real shooting scenarios delivers different results.

What your calculator tells you, and what the real images show, are going to differ for a number of reasons -- not the least of which is that when something's in focus on the GH1, it's way sharper than it is on the HMC150. Therefore, the perceived depth of field is going to be notably shorter on the GH1. The transition from in-focus to out-of-focus is more noticeable on the GH1. Yet that isn't accounted for in an online DOF calculator.

I can force a 35mm movie camera to deliver deeper depth of field than an HMC150. Does that mean I should go around thinking that the HMC150 has shallower DOF than a 35mm movie camera? Of course not, the notion is silly on the face of it.

Yet, seeing as the GH1 has nearly the same sensor size as a 35mm movie camera, that's the premise you're asking us to accept. And, as a logical individual and an experienced shooter, I reject that notion.

If I can squeeze some time in, maybe I'll do some sample shots. It's too bad I don't live in an area where I can find some straw, I'd love to use a "straw man" as my subject.

 

[Barry_Green]

You have to actually go get a GH1 and put it next to the HMC and shoot along. You have to prove your point in the real world, out in the field with proper samples. Then if you are right you would have proven your point with actual images from the cameras you are debating about.

But only if you want to hamper the GH1 by always forcing it to be several stops slower than the 150.

 

[Barry_Green]

Okay, the great "straw man shootout 2009" is now complete.

I constructed a "straw man". Put it on my porch railing, and set the cameras as far away as I could get them (about 6'). The background is intensely detailed trees, about 40' behind the "straw man".

Both cameras opened up to their maximum iris. In the case of the HMC150, that's about f/2.0, in the case of the GH1 that was f/5.8. (I say "about f/2.0" because it was set to read "open"; if I stopped it down one tick it read out as "f/2.4", so it was more open than f/2.4, putting it at "about" f/2.0). The HMC150 had ND1 employed to keep the iris as open as possible. The GH1 was set to ISO 100 to keep the iris as open as possible.

GH1 was 1/50th shutter. I actually cheated a little to help the HMC150; I used 1/100, trying to get the proper exposure in the background. That's unfair, I should have stopped down the iris, but hey, I'm trying to put the HMC150 in its best possible light for purposes of the comparison.

HMC150 and GH1 were both zoomed in to the point where they could see the straw man top to bottom in the frame. On the GH1 that was about 120mm, on the HMC150 it was 33.3mm.

Here are the results. HMC150 on the left, GH1 on the right. If the DOF looks exactly the same to you, so be it. I happen to see a substantial difference, as expected. (note, this image has been resized down to fit on most people's screens; the originals are available after the pic).

For those who want to examine the original 1080p frames, here they are:
http://dvxuser.com/barry/GH1-Straw-Man.jpg
http://dvxuser.com/barry/HMC150-Straw-2.jpg

 

[studio1972]

You have to actually go get a GH1 and put it next to the HMC and shoot along. You have to prove your point in the real world, out in the field with proper samples. Then if you are right you would have proven your point with actual images from the cameras you are debating about.

Well, that's kind of difficult for me to without having a GH1, but I've taken an image with the HMC and with a 450d with aperture f/5.6. The images are attached. The DOF from the HMC is slightly less shallow, as I said, but not that much. I think that proves my point pretty well, given that I thought my original point was only a simple calculation based on the specs of the HMC and GH1.

 

[Ben_B]

Thanks Barry. GH1 wins for sure, and the HMC shot is STILL OVEREXPOSED. Also the expression on the straw man's face is exactly what I imagined your face to look like arguing this point. f/5.6 beating the crap out of f/2...wow.

To address some things mentioned earlier. You can use ND filters on the GH1 if you want.

Claiming that using Prime Lenses on the GH1 gives you less flexibility is totally preposterous: you can't use prime lenses on the HMC-150, you're stuck with the stock lens! I can use just about any lens every made on the GH1 and I can carry them around in a little bag and swap whenever I want, all I need to do is buy a few $100 adapters. People are using everything from C-Mount security camera lenses to PL cinema lenses on the thing and everything in between. If you want to throw a Nikon lens on the HMC-150 that'll set you back about $2,000 for the adapter and the rail system. And with the GH1 you're saving about $4000 ($4900 if you speak Japanese and bought body-only) cash vs HMC + Adapter which you have to spend on all the glass you want to get all the flexibility in the world. On top of that if you don't think I can find a zoom that performs as well as the HMC's stock lens for that amount of coin then I propose you send me the $2000 difference between the two camera's stock configurations (although more fair would be the $2900 between GH1 body only and the HMC) and I'll send you some pictures. Tell me which camera has less flexibility!