3120mm effective 1080p? 1dc

[Shield3]

So at the end of July I went out to my wife's parents house and climbed a steep hill and got some shots.

Please look at the 2nd picture first - note the outlined area I circled in red with MSPAINT (super high tech I know).  That's how far away I was.

This started at 24mm then went to 600mm, then cropped at 1080p.  I throw on the Sigma 150-600 full tele.

So my math (and correct me if I'm wrong) - this should be 3120mm focal length right?

600 x 1.3 (in 4x) cropped to 1080p = 780mm, then a 4x crop to 1080 = 3120mm.  Is that right?  I was pretty impressed with the range. 

 

Note - I'm not trying to make the next Cannes film festival.  This is just for fun; not looking for "you blew the highlights" critique.  I'm sure I made plenty of mistakes.  It was hot and I was tired. 

 

Here's the video:

 

 

 

[Guest Ebrahim Saadawi]

Impressive. If you'd increase contrast a bit aggressively in post on the long shots the haze/heat/waves would not be apparent and get normal looking footage.

I think the math is 600*1.3 = 780mm,

Cropping 4k to 1080p is a 2.2x not 4x crop,

So 780*2.2x = 1700mm-ish HD video (photographic 35mm equivalent)

[Shield3]

Where did you get this 2.2x number?  Just curious.  Is this for true 4k (4096x2160) or UHD (3840x2160)?

I will go test this myself.  16mm x 2.2 = 35.2mm (both will have the 1.3x on top of that, but should be close). 

[Shield3]

It's really close to 2.2.  Probably 2.3, but of course the 16-35 F/4 might not exactly be 16mm @ the wide end, nor 35mm @ the "long" end.

Seems the 16mm shot cropped to 1080p was slightly tighter than the non-cropped 4k 35mm.

In Edius I had to set the x/y to about 95%.

So based on this non-scientific test it's probably 2.3x for full 4k.

[Inazuma]

 

Cropping 4k to 1080p is a 2.2x not 4x crop,

So 780*2.2x = 1700mm-ish HD video (photographic 35mm equivalent)

4096 x 2160 = 8847360

1920 x 1080 = 2073600

8847360 / 2073600 = 4.3 

So the effective focal length is actually 3354mm.  Not bad!

Or maybe I'm missing another step in my calculation?

[MattH]

4096 x 2160 = 8847360

1920 x 1080 = 2073600

8847360 / 2073600 = 4.3 

So the effective focal length is actually 3354mm.  Not bad!

Or maybe I'm missing another step in my calculation?

I will assume irony.

[Cinegain]

How exactly would that be ironic?

The crop cuts from two sides at once, not just one. To consider both axis, use pythagoras to get the diagonal pixelcount. Which is roughly 4631 for C4K and 2203 in FHD. This results in a factor difference of 2.1x, actually.

Or maybe I'm missing another step in my calculation?

'Illuminati confirmed', as the interw3bz would say.

[The Chris]

The math makes my head hurt, but this is cool. Easy to see how paparazzi get topless shots of celebrities from a couple miles away. Someone is always watching....

[MattH]

How exactly would that be ironic?

The crop cuts from two sides at once, not just one. To consider both axis, use pythagoras to get the diagonal pixelcount. Which is roughly 4631 for C4K and 2203 in FHD. This results in a factor difference of 2.1x, actually.

Or maybe I'm missing another step in my calculation?

'Illuminati confirmed', as the interw3bz would say.

I think you answered your own qestion. : )  Its 2.1, nowhere near 4.3.  As you identified, crop factor is a ratio of length not of area, which is why I asumed Inazuma was joking.

In fact, if the sensor ratios are the same, the ratio for the width or height is exaclty the same as the ratio of the diagonal.

[Inazuma]

I think you answered your own qestion. : )  Its 2.1, nowhere near 4.3.  As you identified, crop factor is a ratio of length not of area, which is why I asumed Inazuma was joking.

In fact, if the sensor ratios are the same, the ratio for the width or height is exaclty the same as the ratio of the diagonal.

Regardless of the 'crop' in photographic terms, he is taking about a quarter crop of the 4k image. So the resulting focal length would be 4x that of the lens (with consideration to the sensor crop). 

It's like if you shoot with a 25mm lens, took a picture and then put on a 50mm lens and took a picture. If you scaled the second image down to 50%, everything in view would line up with the central 50% of that first 25mm image. 

[TheRenaissanceMan]

Wouldn't it be half though? Because when you reduce the image to one quarter, you're only halving the diagonal field of view. 

[MattH]

Regardless of the 'crop' in photographic terms, he is taking about a quarter crop of the 4k image. So the resulting focal length would be 4x that of the lens (with consideration to the sensor crop). 

It's like if you shoot with a 25mm lens, took a picture and then put on a 50mm lens and took a picture. If you scaled the second image down to 50%, everything in view would line up with the central 50% of that first 25mm image. 

Sorry sir, you are mistaken.  Using your own example.   In fact your own example isn't even true.  So you are doubly mistaken unfortunately.

Firstly, Angle of view doesn't scale that perfectly with respect to focal length.  A 25mm lens on full frame will give you a horizontal angle of view of 71.5 degrees.  If you were correct a 50mm would give half that which is 35.75 degrees. But it doesn't. A 50mm gives you 39.6 degrees.  The higher you get in focal length the less difference it makes.

However if you had said a 25mm lens and a 56mm lens you would have been correct.  The picture area of the 25mm would be four times greater than the picture area of the 56mm.   But lets take a simpler example.  A full frame sensor is 36mm wide and a four thirds sensor is 18mm wide. Half as wide.  Because we are talking about video we can assume a 16:9 ratio in each case, so we know that the full frame sensor is 4 times greater in area than the four thirds sensor.   But as we know, crop factor for four thirds is 2.  A 25mm on four thirds will give you the equivalent of 50mm on full frame, not the equivalent of 100mm on full frame.  As far as crop factor and equivalents are concerned it's the lengths that matter, not the area.

[MattH]

This has made me wonder which cameras will give you the greatest reach.
I’ve worked out the active sensor width at native QHD on various cameras.

GH4 is 14.41mm which is 2.497* crop.
NX500 is 13.92mm which is 2.58* crop.
Micro Studio Camera is 13.056mm which is 2.75* crop.

So 600mm with these cameras will give:

GH4: 1498mm
NX500: 1548mm
Micro Studio: 1650mm

If you crop to 1080, the result will obviously be double which is:

GH4: 2996mm
NX500: 3096mm
Micro Studio: 3300mm

By the way the active sensor width when you crop to 1080 native on a 1DC is 13.33mm which gives 2.7 crop.

So your 600mm is giving you 1620mm equivalent.

[Inazuma]

Sorry sir, you are mistaken.  Using your own example.   In fact your own example isn't even true.  So you are doubly mistaken unfortunately.

Firstly, Angle of view doesn't scale that perfectly with respect to focal length.  A 25mm lens on full frame will give you a horizontal angle of view of 71.5 degrees.  If you were correct a 50mm would give half that which is 35.75 degrees. But it doesn't. A 50mm gives you 39.6 degrees.  The higher you get in focal length the less difference it makes.

I figured you might say something like this, so I took a very quick picture earlier. The attached picture was taken with my Tamron 17-50mm. The centre image was taken at 50mm and scaled down 50%. The rest of the image was taken at 25mm. See how closely they match up? Actually, Wikipedia and B&H both show that 50mm lens gives about half the angle of view of a 24mm lens. 

So with that logic in mind (that the central 50% of a photo is the same angle of view as what you would get with a lens that has double the focal length), its safe to safe the inverse is true. Therefore 600 * 1.3 = 780. Then * 4 = 3120.

Also I think there's no way the OP's video there is equiv to 'just' 1700mm. It's gotta be closer to 3000mm+

[Guest Ebrahim Saadawi]

An HD window from UHD/4K = 2.2x-ish crop. 

OP video is 1700mm-ish photographic 35mm equivalent, in other words, pretty £$^&ing long.

[MattH]

I figured you might say something like this, so I took a very quick picture earlier. The attached picture was taken with my Tamron 17-50mm. The centre image was taken at 50mm and scaled down 50%. The rest of the image was taken at 25mm. See how closely they match up? Actually, Wikipedia and B&H both show that 50mm lens gives about half the angle of view of a 24mm lens. 

So with that logic in mind (that the central 50% of a photo is the same angle of view as what you would get with a lens that has double the focal length), its safe to safe the inverse is true. Therefore 600 * 1.3 = 780. Then * 4 = 3120.

Also I think there's no way the OP's video there is equiv to 'just' 1700mm. It's gotta be closer to 3000mm+

Im not trying to be contrary at all here, but everything I have said is objective fact.

On APS-C a 50mm will give you a 2 times zoom over 23.7mm so yeah you are getting very close with 24mm, but the fact is that it doesn't scale linearly.

As for the *4 vs *2 thing, I don't know how I can put it better than the four thirds example.

[Guest Ebrahim Saadawi]

This has made me wonder which cameras will give you the greatest reach.
 

Think simpler.

Just the one with highest pixel density,

and because the number is of pixels is constant,

the answer to your question is the camera with smallest 4K sensor. 

Speaking about interchangeable-lens cameras,

the Samsung NX500 is the smallest (having an enormous UHD resolution in a dense 2.75x crop area yet with gorgeous quality)

 

(The only other smaller 4K sensor camera I can think of is the s16 Studio Camera from BM, which has maximum 200ISO, never-seen-before aliasing, 7 stops of television rec709 DR, and doesn't record video. It's only really for its specific purpose don't buy it as a 4K version of the pocket/micro camera, huge mistake)

 

You can find smaller 4K sensors, for example if you remove the Note 3/4 casing (the lens) and build a physical adapter that but your lenses at the correct distance, you'll get 6x crop factor for your lenses. A 600mm is a 8000mm HD, Great image too just under daylight

 

[MattH]

Think simpler.

Just the one with highest pixel density,

and because the number is of pixels is constant,

the answer to your question is the camera with smallest 4K sensor. 

Speaking about interchangeable-lens cameras,

the Samsung NX500 is the smallest (having an enormous UHD resolution in a dense 2.75x crop area yet with gorgeous quality)

 

(The only other smaller 4K sensor camera I can think of is the s16 Studio Camera from BM, which has maximum 200ISO, never-seen-before aliasing, 7 stops of television rec709 DR, and doesn't record video. It's only really for its specific purpose don't buy it as a 4K version of the pocket/micro camera, huge mistake)

 

You can find smaller 4K sensors, for example if you remove the Note 3/4 casing (the lens) and build a physical adapter that but your lenses at the correct distance, you'll get 6x crop factor for your lenses. A 600mm is a 8000mm HD, Great image too just under daylight

 

The pixel density is exactly what I worked out.  

The camera with the smallest 4k sensor is the first question I asked.  Everything after that was answering that question.

The Samsung NX500 does not have a crop factor of 2.75. It has a crop factor 2.58 as I worked out above using the sensor width and horizontal resolution to find the actual active width at 3840.  (2.75 sounds like a nice tidy marketing figure).

The studio 4k and micro studio look like they have the same sensor and do have a crop of 2.75, but as you say you need a recorder and there doesn't seem to be much footage from it out there. 

Overall there isn't that much between them when you have a 600mm lens at hand, so I agree the nx500 and gh4 would probably be better choices.

As for the smaller sensors, I would certainly like to see someone rig one up with a 600mm lens.  I suppose the problem is that the smaller part of the lens you use the less sharp it gets.  1500mm equiv' in 4k sounds pretty damn good.

[Shield3]

I'm going to, in my mind, call it 2.2x 1080p crop from the 1dc 4096x2160 and call it a day.  I would ask what the 1dc 3840x2160 is, but it doesn't shoot that resolution so who cares.

My head hurts.  I will say it seemed like more than 1700mm to me as well, but what the hell do I know.  I will say I was on top of that hill and I'd say that boat was at least 3/4 of a mile away as I used to jog that distance and come back all the time.

Next time I go up - I will add the 1.4x teleconverter.

So - 1.3 x 600mm = 780mm.  780mm x 1.4 = 1092.  x 2.2 = 2400.4mm.  Dare I stack the 2x tele?    I would but I don't own one.

 

At any rate, thanks.

[Guest Ebrahim Saadawi]

The Samsung NX500 does not have a crop factor of 2.75. It has a crop factor 2.58 as I worked out above using the sensor width and horizontal resolution to find the actual active width at 3840.  (2.75 sounds like a nice tidy marketing figure).

I agree with every word.

I wonder why noone is making a camera with a lens mount for all those great 1" 4K sensors (2.7x). An XC10 with an EOS-M mount, or a RX10 with an E-mount.

However about the nx500, the official Samsung number is actually that the sensor is 30.3mp total count, and 28mp are used, so it's a 1.55x crop over FF, then in UHD it's an additional 1.77x crop to that, so their official number is 2.74x in UHD.

That's what the company says anyway if we trust them. They didn't give a number for DCI mode but of course you get a few pixels wider on each side horizontally. Anyhow it's here nipticking, let's just say they're about 1" size image aesthetic in 4K as the RX10, XC10, 

I really see the potential for a high quality small sensor camera with an interchangeable lens mount with 4K resolution, something smaller than 1" sensors, It would be the only telephoto/sports/wildlife video option for the consumer market.

1" size is specifically ideal as it can be used for normal cinema applications with s16 cine glass and for sports/wildlife applications we're talking about here,  

Small sensors are great now (in good light), the 4K image out of the Note 4 I have with that TINY 6x crop chip is absolutely mindblowing, as a wide landscape shooter it's better than ''most'' DSLRs/mirrorless cameras we're using in that wide bright aspect, never imagined such an image could be created on such a tiny chip. Sony make great small sensors obviously and are open to selling them. 

They still do have their place and there's a market open for a small sensor solution. Even Panasonic's highest-end 60K cinema camera offers a 2/3" sensor head with a lens mount for sports/wildlife so it's clearly needed and people pay cinema-camera prices for them. 

Having a FF lens is such a pain to get long shots, look at the Canon good old 1200mm or the sigma 200-500mm, I mean that's ridiculous  

 I will say it seemed like more than 1700mm to me as well, but what the hell do I know.  

Your OP video is pretty £¢€¥ing long. As long as they get, I have huge doubt anybody needs more than that for any application, perhaps moon shots or well, stalking god knows who