Crop sensors need cropped lenes

[rs]

The size and weight of all telephoto lenses is largely driven by their physical length, and the size of the front element. Those two factors are driven purely by focal length and aperture. For instance, get a 300/4, and with a simple bit of mathematics you can calculate the front element will be a quarter of 300mm - and the filter size is a very close match at 77mm. The 85/1.2 should have a theoretical 71mm front element, and it's filter size is 72mm. And so on.

This formula holds true for most lenses until the angle of view gets wider than about 45 degrees. At that point, the aperture is no longer dictates the size of the front element. Otherwise we would have a 14/2.8 with a 5mm diameter front element (entirely possible in a compact where the AoV is narrower than 45', but not possible on a FF DSLR).

It is with lenses wider than about 45 degrees AoV that they can be made smaller for these smaller imaging circles. Which is why normal zooms and ultrawides are typically made for crop sensor DSLR's, and no-one to my knowledge makes a crop only telephoto lens who's angle of view is (at its widest setting) much narrower than 45 degrees.

 

[Sporgon]

The OP's got a point, and there are systems out there that fit the bill. Look at the Pentax 50-135 f2.8. It is much smaller and lighter than the FF equivalent 70-200 f2.8. The FF producers don't seem inclined to produce this kind of kit, probably for the reasons others have mentioned.

 

[Skulker]

The OP's got a point, and there are systems out there that fit the bill. Look at the Pentax 50-135 f2.8. It is much smaller and lighter than the FF equivalent 70-200 f2.8. The FF producers don't seem inclined to produce this kind of kit, probably for the reasons others have mentioned.

Thanks Sporting. That's what I was thinking of, it's half the weight for an equivalent image, I guess I really mean field of view. The quality may not be big white equivalent but nor is the price.

This example makes me think it would be possible to have much lighter systems that were close in quality.

I still don't think it will happen but I would like to see this more than a high megapixel camera.

 

[rs]

The OP's got a point, and there are systems out there that fit the bill. Look at the Pentax 50-135 f2.8. It is much smaller and lighter than the FF equivalent 70-200 f2.8. The FF producers don't seem inclined to produce this kind of kit, probably for the reasons others have mentioned.

Thanks Sporting. That's what I was thinking of, it's half the weight for an equivalent image, I guess I really mean field of view. The quality may not be big white equivalent but nor is the price.

This example makes me think it would be possible to have much lighter systems that were close in quality.

I still don't think it will happen but I would like to see this more than a high megapixel camera.

That Pentax lens, mounted to a Pentax body with its 1.5x crop factor is the direct equivalent of a 75-202/4.2 lens. Canon have the 70-200/4 L lens, which shares the same size filter size, is less than 3% heavier, and is 38% cheaper here in the UK. Admittedly the FF Canon lens is 26% longer, but the OP is mostly interested in weight saving. 3% more weight for 10% more light gathering is a good deal in my eyes, especially when you throw in the huge cost saving.

Also, if you're just after lightweight reach, the 70-200/4 when used on a crop camera is much a better compromise than a 50-135/2.8, even when you count the extra 3% weight.

 

[Sporgon]

You'll open a whole can of worms with the 2.8 on APS is equal to 4.2 FF thing.

A 2.8 lens is just that: 2.8. Yes due to the different COC the depth of field equivalent is 'slower' on the smaller format in resulting dof. ( I believe it's more like 3.2-3.6 depending on exact format). But the difference is really over stated here on CR IMO.

You are still getting the fundamental benefits of a 2.8 lens.

At Building Panoramics we've used FF since 2005, but I'm sure we could use APS to achieve the same thing.However with present technology certainly prefer the results from the less dense sensors such as the 1100D to say a 7D.

You're quite right on the price of the Pentax lenses. They look very poor value next to Canon, and the 70-200 f4 L is much more substantially built.

 

[Skulker]

The issue of a cropped 2.8 and equivalence to 4.2 FF is sure to get some folks wound up and may well produce some long posts. ;D

My view would be that with any lens designed to be used on a crop sensor, most of the photons entering the lens will hit the sensor, subject of course to the rectangular sensor reading a round lens. In contrast only 40% of the photons that would have hit the sensor on a full frame body will be used in a crop body (assuming a 1.6 crop) with a FF lens.

I'm getting more convinced that long lenses specifically designed for crop bodies would have a weight benefit. I still can't see Canon or Nikon making them. But maybe someone like Sigma might just do it to give themselves a USP.

 

[rs]

The issue of a cropped 2.8 and equivalence to 4.2 FF is sure to get some folks wound up and may well produce some long posts. ;D

I'm keeping my mouth shut about that one from now on :-X

 

[Pi]

You'll open a whole can of worms with the 2.8 on APS is equal to 4.2 FF thing.

A 2.8 lens is just that: 2.8.

http://www.josephjamesphotography.com/equivalence/#1

2.8 is a denominator in a ratio, actually. You are forgetting the numerator. What you really mean, is, say, 50/2.8 is 80/2.8, and that is wrong.

 

[Loswr]

You'll open a whole can of worms with the 2.8 on APS is equal to 4.2 FF thing.

A 2.8 lens is just that: 2.8.

http://www.josephjamesphotography.com/equivalence/#1

2.8 is a denominator in a ratio, actually. You are forgetting the numerator. What you really mean, is, say, 50/2.8 is 80/2.8, and that is wrong.

So you're saying the sensor size changes the numerator (focal length), and that's wrong, too. Focal length and max aperture are intrinsic properties of a lens, the sensor doesn't change them.

 

[Pi]

You'll open a whole can of worms with the 2.8 on APS is equal to 4.2 FF thing.

A 2.8 lens is just that: 2.8.

http://www.josephjamesphotography.com/equivalence/#1

2.8 is a denominator in a ratio, actually. You are forgetting the numerator. What you really mean, is, say, 50/2.8 is 80/2.8, and that is wrong.

So you're saying the sensor size changes the numerator (focal length), and that's wrong, too. Focal length and max aperture are intrinsic properties of a lens, the sensor doesn't change them.

No, the sensor size does not change the FL. You are changing it, to get the same picture.

How often do you shoot with your smartphone at 200mm?

 

[Loswr]

So you're saying the sensor size changes the numerator (focal length), and that's wrong, too. Focal length and max aperture are intrinsic properties of a lens, the sensor doesn't change them.

No, the sensor size does not change the FL. You are changing it, to get the same picture.

Maybe I'm not changing focal length, just moving forward or back... Or maybe I'm taking a different picture.

How often do you shoot with your smartphone at 200mm?

Just once, when I mounted my 70-200 II on my iPhone with an iPhone-to-EF Mount Adaptor that I borrowed from a friend.

 

[Mt Spokane Photography]

I used to have a 7D. A camera I took many pictures with and really enjoyed. But I was using it mainly behind L series lenses because I wanted the quality that those lenses provide. This has proved to be a good investment as I now have a 5D3 and a 1Dx and the lenses work with them.

I don't want more megapixels, I've got more than I uses almost always. And before anyone suggests it I certainly don't want more just so I can crop them away.

One of my main problems with all this kit is the weight, carrying 40Kg on a trek to a wild life photo opertunity can be a pain.

When the 7D2 comes out the thing that would get me to buy one would be if light weight lens were available with similar quality to the L series but making use of the reduced diameter needed for the smaller sensor. (While they are at it they can reduce the price as the elements aren't as big. )

I know its not going to happen but it would be nice if it did. ------- Just think a nice quality 200-400 with built in 1.4x at about 1/2 the weight and cost in front of a crop sensor giving equivalent view to a 300 to 900 on a FF. 8)

( BTW There can be little doubt that someone who thinks they know better will ridicule this idea. If they convince me that they are right I will claim I was being sarcastic ;D )

Also forgot to say, yes I'm carrying a couple of ff bodies and several big whites plus tripods flashes a hide a chair, it all adds up.

But ...Those tripods and flashes and hide a chair are still needed, its only the lenses that will change. Flashes don't get smaller due to sensor size, in fact, they might get bigger to keep ISO's lower.

We are certainly not going to see the big white equivalent of a EF-s, there would be no market. the price is determined in part by the number produced and sold, so a item that does not have a lot of sales must pay for R&D, and tooling over fewer units, the price then takes a jump.

I think we all wish for lighter and less expensive lenses while retaining or improving lens quality.

 

[Pi]

So you're saying the sensor size changes the numerator (focal length), and that's wrong, too. Focal length and max aperture are intrinsic properties of a lens, the sensor doesn't change them.

No, the sensor size does not change the FL. You are changing it, to get the same picture.

Maybe I'm not changing focal length, just moving forward or back... Or maybe I'm taking a different picture.

Are we still talking about the Pentax 35-70 on crop vs. the 70-200 on FF? If you are taking a different picture, then this would be a different conversation. You can take different pictures with the same combo, as well.

How often do you shoot with your smartphone at 200mm?

Just once, when I mounted my 70-200 II on my iPhone with an iPhone-to-EF Mount Adaptor that I borrowed from a friend.

Would you post the result? That wold be interesting to see!

 

[moreorless]

The discussion really seems to be focused on two different things...

1.Making a smaller/cheaper lens for ASPC with the same focal length.

2.Making a smaller/cheaper lens for ASPC with the same field of view.

The second clearly being possible while the first probably isn't.

My guess is that with crop cameras the market for a lens with 70-200mm FOV isn't that great, that range seems to be well suited for things like event photography and I'm guessing most pro's are going to be using FF. On ASPC I think the demand is much more long longer fast lenses for wildlife/sports use.

 

[Loswr]

Are we still talking about the Pentax 35-70 on crop vs. the 70-200 on FF? If you are taking a different picture, then this would be a different conversation. You can take different pictures with the same combo, as well.

I wasn't, ever. Sprogon stated that f/2.8 is f/2.8, and you apparently disagreed.

How often do you shoot with your smartphone at 200mm?

Just once, when I mounted my 70-200 II on my iPhone with an iPhone-to-EF Mount Adaptor that I borrowed from a friend.

Would you post the result? That wold be interesting to see!

It really wouldn't - I just used it out the window of my 8th floor office.

However, what was I actually using?

1) 70-200mm f/2.8,
2) 535-1528mm f/2.8, or
3) 535-1528mm f/21?

Sounds like I'd say #1, you'd say #3, and Panasonic would print #2 on the side of their lens barrel, like they do on the Lumix FZ200. :

 

[Etienne]

I have a Tokina 50-135 f/2.8 equiv to 80-112 mm.
It's a great lens. Much smaller than my 70-200L 2.8 IS II. BONUS: It is par-focal and that makes a big difference in video.
Pair that with a Tokina 11-16 f/2.8 and it is a great light-weight package for crop.
You could also add Sigma 30 1.4 and/or Canon 50 1.4.

 

[Daniel Flather]

If I won a big lottery I'd put out a bounty for someone to build a lens like that if Canon didn't take it up.

Or just buy what's current and hire a assistant to haul your sh*t around.

 

[Pi]

However, what was I actually using?

1) 70-200mm f/2.8,
2) 535-1528mm f/2.8, or
3) 535-1528mm f/21?

Sounds like I'd say #1, you'd say #3, and Panasonic would print #2 on the side of their lens barrel, like they do on the Lumix FZ200. :

You were shooting (1), which was equivalent to (3); and (2) is wrong any way you look at it.

 

[Loswr]

However, what was I actually using?

1) 70-200mm f/2.8,
2) 535-1528mm f/2.8, or
3) 535-1528mm f/21?

Sounds like I'd say #1, you'd say #3, and Panasonic would print #2 on the side of their lens barrel, like they do on the Lumix FZ200. :

You were shooting (1), which was equivalent to (3); and (2) is wrong any way you look at it.

Someone should tell Panasonic...

 

[Pi]

However, what was I actually using?

1) 70-200mm f/2.8,
2) 535-1528mm f/2.8, or
3) 535-1528mm f/21?

Sounds like I'd say #1, you'd say #3, and Panasonic would print #2 on the side of their lens barrel, like they do on the Lumix FZ200. :

You were shooting (1), which was equivalent to (3); and (2) is wrong any way you look at it.

Someone should tell Panasonic...

A good lawyer?