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02-06-2014, 04:23 PM   #151
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QuoteOriginally posted by tuco Quote
That's nothing. Sports and wildlife photographers haul around lenses that weigh more. It's MFD not a APS-C mirrorless.
But this isn't about wildlife but wide angle. A super wide angle zoom lens for the FF 645 system weights 500g. The 25mm on a cropped sensor weights more than twice as much. In addition you have a 1.5kg camera not to mention if you want to use telephotos as well where theres no way around size and weight. The cropped sensor make the angle of view of some lenses into something awkward like the 75mm that has the angle of view of a 60mm lens on 35mm FF. I've never wanted a 60mm lens.
The 645's have also been markted as field cameras. Wide angles that weights more than wide angles for even the 67 is not compatible with this. This is a camera ideal for landscapes. The 645 film system could compete with high-end 35mm system in terms of weight. The digital 645 could as well if it was FF. If you want a wide angle a 645 FF may have been no more expensive in total and you might have saved 1kg in weight. 1kg is a lot when it is the last kilo, the one you could have been without.

02-06-2014, 04:30 PM - 1 Like   #152
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I have never been overly concerned with size and weight of my camera gear and though the 645 isn't a walk-around cam, I would most certainly have it with me on vacation trips. There was nothing more frustrating when I found myself in Tuscany with nothing more than a pocket-cam for documentary style shots while my DSLR was sitting back in the hotel room. I missed some phenomenal opportunities and I vowed never to do that again.
02-06-2014, 05:05 PM   #153
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QuoteOriginally posted by Pål Jensen Quote
But this isn't about wildlife but wide angle. A super wide angle zoom lens for the FF 645 system weights 500g. The 25mm on a cropped sensor weights more than twice as much. In addition you have a 1.5kg camera not to mention if you want to use telephotos as well where theres no way around size and weight. The cropped sensor make the angle of view of some lenses into something awkward like the 75mm that has the angle of view of a 60mm lens on 35mm FF. I've never wanted a 60mm lens.
The 645's have also been markted as field cameras. Wide angles that weights more than wide angles for even the 67 is not compatible with this. This is a camera ideal for landscapes. The 645 film system could compete with high-end 35mm system in terms of weight. The digital 645 could as well if it was FF. If you want a wide angle a 645 FF may have been no more expensive in total and you might have saved 1kg in weight. 1kg is a lot when it is the last kilo, the one you could have been without.
That's fine. I understand. But here we go already trying to make a MFD small mirrorless size system and complaining that it's not. This new CMOS sensor is new. They happen to make it a crop sensor. Give it time and one day perhaps a FF CMOS 6x4.5 format sensor will come out. You can get that in CCD already.

BTW, in the modern SI metric system, weight = mass x gravity

Units of gravity = meters per second^2
Units of mass = kilograms

Multiply mass x gravity and the units equal:

(kilogram) (meters)/ seconds^2

That is the fundamental units of weight and a far cry from just kilograms. Perhaps someone can explain why metric countries don't use the modern SI metric system when it comes to weight but use the modern system for all the other units.
02-06-2014, 05:59 PM   #154
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Pentax 645D with wide angle too heavy for field work ?

I carry around my Pentax K-5 with battery grip attached and extra battery in the grip. Attached to the K-5 is a Sigma 150-500. Heavy stuff. I regard it as a field camera/lens.

I often go for treks down winter forest trails with this equipment. I'm old and on the large side. I generally carry the combo using the Sigma's lens handle. I will swap the combo from hand to hand.

I'm sure the time will come when it's too heavy...but until then.

Back in the film days....when I was younger... I used to carry a medium format Mamiya TLR with a Mamiya-Sekor 180mm super telephoto, attached to my heavy aluminum Leitz Tiltall tripod.

My point is....if you want to use particular equipment...whether it is heavy or not...usually you can find a way.

Heavy to one person maybe different to another. All we can do is the best we can individually handle.

02-06-2014, 06:42 PM - 1 Like   #155
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QuoteOriginally posted by tuco Quote
That is the fundamental units of weight and a far cry from just kilograms. Perhaps someone can explain why metric countries don't use the modern SI metric system when it comes to weight but use the modern system for all the other units.
Because for all intents and purposes, for all objects of a negligible fraction of the Earth's mass (~6,000,000,000,000,000,000,000,000 kg), weight is directly proportional to mass, in that a 2kg object will have double the weight of a 1kg object. The distinction between newtons and kilograms is insignificant for non-engineering applications near the surface of the Earth. For everyday people, it adds a completely unnecessary step to calculations with units for which there is otherwise a straightforward equivalence.

Or do you also wonder about why people measure some things like sugar or salt in terms of volume, instead of mass, when its involvement in a recipe has nothing to do with volume (e.g. adding a cup of sugar to a pot of water has nothing to do with adding a cup of volume to it)?

As a side note, the mass of an object is impossible to empircally measure directly (unless you can count individual atoms). It can only be determined indirectly through the application of an external force, such as gravity.

Last edited by Cannikin; 02-06-2014 at 06:53 PM.
02-06-2014, 07:02 PM   #156
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QuoteOriginally posted by Cannikin Quote
Because for all intents and purposes...
Great, tell that to your engineering professor when he marks your answer wrong when you're asked to calculate a reaction force with am answer in kilograms.
02-06-2014, 07:04 PM   #157
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QuoteOriginally posted by tuco Quote
Great, tell that to your engineering professor when marks your answer wrong when you're asked to calculate a reaction force with am answer in kilograms.
Did you even read the first sentence?

Maybe your engineering professor introduced you to this formula: http://en.wikipedia.org/wiki/Newton%27s_law_of_universal_gravitation, you know the one that explicitly defines a directly proportional relationship of mass to gravitational force, a.k.a. weight?

Last edited by Cannikin; 02-06-2014 at 07:15 PM.
02-06-2014, 07:06 PM   #158
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A D800 with a Tokina 16-28mm f2.8 ATX Pro is 2 kilos. That's also a pretty solid landscape kit. I bet the 645 kit is heavier, but still the FF option isn't exactly light weight.

02-06-2014, 07:23 PM   #159
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QuoteOriginally posted by Cannikin Quote
Did you even read the first sentence?
Yep. And what fudge factor do you use to make the units of kilogram pop out of this equation when you calculate a force with a 1 kilogram mass?

F = (mass) x (9.81 m/s^2)
02-06-2014, 07:29 PM   #160
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QuoteOriginally posted by Wired Quote
A D800 with a Tokina 16-28mm f2.8 ATX Pro is 2 kilos. That's also a pretty solid landscape kit. I bet the 645 kit is heavier, but still the FF option isn't exactly light weight.
That is very true but a Pentax 645D with the 33-55 weigths about the same. That is partly what makes it a compelling alternative....
And the 75/2.8 weights only 215g!
02-06-2014, 07:54 PM   #161
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QuoteOriginally posted by tuco Quote
Yep. And what fudge factor do you use to make the units of kilogram pop out of this equation when you calculate a force with a 1 kilogram mass?

F = (mass) x (9.81 m/s^2)
Are you hoping to impress someone with your knowledge of elementary physics? Or do you realize that your own reasoning of giving weight as "F = m(9.81m/s^2)" is itself a mathematical shortcut born out of an observation of a real world relationship, and not a proper definition, just like the relationship between mass and weight?

How about this: An object at rest on the Earth's surface has no acceleration relative to it (ignoring the Earth's rotation). F = ma = m(0) = 0? Whoops.

Your "9.81m/s^2" figure comes from an observation that objects of negligible mass compared to the Earth will appear to accelerate towards the Earth without the application of another external force (i.e. freefall without air resistance), from the frame of reference of the Earth, at approximately 9.8 m/s^2 near the surface. This is not the "proper" way to determine force of gravity, which is given by Newton's law of universal gravitation (unless you want to get into Einstein's General Relativity). Once you have that figure, you can work out the acceleration from the definition of the unit "newton": a = f/m, giving you your shortcut of F = m(g).

Now you can accept that there are mathematical relationships between units of measurement for which a distinction is not meaningingful a difference in everyday non-engineering applications, or you can go around quoting everything (and converting everything) in "newtons", "pound-force", or whatever, and see whether it makes any meaningful difference in everyday life, or if it is just adding another unnecessary calculation to an otherwise relatively consistent and straightforward relationship.

Last edited by Cannikin; 02-06-2014 at 08:41 PM.
02-06-2014, 07:55 PM   #162
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QuoteOriginally posted by mee Quote
AW as a matter of fact, provided you keep it indoors.
Yep. I need to digitise some 300 slides using new Pentax duplicator, during the next storm, on top of the lighthouse at -15C.
WR would be wonderful to have.
02-06-2014, 08:30 PM   #163
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QuoteOriginally posted by Cannikin Quote
Are you hoping to impress someone with your "great knowledge" of elementary physics?
Nope. It is a sincere question. We have a fudge factor here in the US for pounds-force/pounds-mass to make the units work. Engineers over in metric countries must deal with the ambiguity all the time of what is mass for calculations vs weight/force when everything is called kilograms for both.
02-06-2014, 08:54 PM   #164
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QuoteOriginally posted by tuco Quote
Nope. It is a sincere question. We have a fudge factor here in the US for pounds-force/pounds-mass to make the units work. Engineers over in metric countries must deal with the ambiguity all the time of what is mass for calculations vs weight/force when everything is called kilograms for both.
If this was an honest question, then I apologize for being a bit snarky.

It all depends on application, whether it makes any real difference. Ultimately it is a matter of accepted practice in each field.

- For everyday life, there is no meaningful difference between mass and weight, as people live near the surface of the Earth and deal with objects of mass very small compared to the Earth. When people refer to weight in kilograms, they implicitly mean kilogram-force, a non-SI unit, just like in the US people rarely say "pound-force". The relationship is more or less constant, and so it is easier to conceptualize if everything is given in the same units, rather than having to do a conversion calculation (e.g. it is not really easy to visualize how much a force really is, until you compare that force to the weight of an object of certain mass that you can visualize).

- In certain engineering applications, when the primary force to counteract is gravitation, some engineers will still rely on the mass-weight relationship shortcut.

- In engineering where dynamic forces other than gravity come into play, then it really makes a difference. Often this involves machinery and other movement, such as in aerospace engineering, fluid mechanics/dynamics, etc. with many different forces in different directions. At that point it is important to work with clearly defined force units and vectors, like newtons.

Last edited by Cannikin; 02-06-2014 at 09:10 PM.
02-06-2014, 09:19 PM   #165
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QuoteOriginally posted by Cannikin Quote
I
...
At that point it is important to work with clearly defined force units and vectors, like newtons.
in other words, if we all just used the SI metric system. Ironically, the old-school hold over of kilograms-force being used instead of Newtons as to not confuse the general public has created confusion. How many people grow up hearing the abbreviated kilograms instead of kilograms-focre and never end up knowing there is a difference when you have to get serious. I think John Q Public can handle it. He has no problem with units such as the Watt. And just like the time scale GMT that has been obsolete for over 40 years ever since the second has been defined atomically instead of astronomically.

Last edited by tuco; 02-06-2014 at 09:26 PM.
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