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Author Topic: Crop sensors need cropped lenes  (Read 20923 times)

TexPhoto

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Re: Crop sensors need cropped lenes
« Reply #15 on: August 09, 2013, 11:31:10 PM »
The closest comparison I can find is:

Crop - Sigma 50-150mm DC OS 76 x 135 mm  1340g - $949
FF    - Sigma 70-200mm OS       87 x 184mm  1390g - $1,249

150 to 200 is a pretty big difference.

150 on a 1.5 crop is 225.  on a 1.6 it's 240.
The lens was actually created and marketed as a way to get a similar range on a crop that a 70-200 provides.  If you have some better examples, tell me.

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Re: Crop sensors need cropped lenes
« Reply #15 on: August 09, 2013, 11:31:10 PM »

Pi

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Re: Crop sensors need cropped lenes
« Reply #16 on: August 09, 2013, 11:46:20 PM »
The closest comparison I can find is:

Crop - Sigma 50-150mm DC OS 76 x 135 mm  1340g - $949
FF    - Sigma 70-200mm OS       87 x 184mm  1390g - $1,249

150 to 200 is a pretty big difference.

150 on a 1.5 crop is 225.  on a 1.6 it's 240.

Also, it is f/4.5 ( eq. to 80-240/4.5). As such, the closest comparison is the 70-200/4 IS, which is $1,150, 760 g, and well, shorter than 240mm but can take some cropping on FF and still be much better that the 50-150 on crop.

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=404&Camera=453&Sample=0&FLI=4&API=0&LensComp=804&CameraComp=736&SampleComp=0&FLIComp=3&APIComp=0
« Last Edit: August 09, 2013, 11:57:29 PM by Pi »

Skulker

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Re: Crop sensors need cropped lenes
« Reply #17 on: August 10, 2013, 12:07:34 AM »
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.  :P

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 )

You must have quite a outfit to weigh 40KG (88 lbs).  Most bodies and lenses are in the 2-3 lb category, the big whites weigh more, so if you used a lot of lenses like the 400mm f/2.8, the weight would add up. 
 
 
A "L" quality 70-200mm f/2.8 EF-s will be smaller, but the "L" treatment with high density glass and fluorite elements will add weight.  It takes more and stronger material to hold those heavy elements securely, and soon there is little weight savings and no cost savings. 
 
IMHO, I really doubt that there is a market for a $1800 70-200mm f/2.8 EF-s lens.  Most would pay the $400 extra for a FF, because they intend to get FF in the future.
 

I agree with much of what your saying and don't expect it to happen.

But although I would expect  the saving in money would not be much I do think the saving in weight could be significant, and in size as well come to that.


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.
« Last Edit: August 10, 2013, 12:30:32 AM by Skulker »
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Skulker

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Re: Crop sensors need cropped lenes
« Reply #18 on: August 10, 2013, 12:24:58 AM »
So now we do a little experiment....

Take a full frame lens and mount it on an APSC camera. Point it at a constant light source.... Something like a white wall under constant illumination.... You don't want something that requires precise positioning to get the same exposure... Set the camera to manual and adjust settings for the proper exposure.....

Now cut out a circle in a piece of dark paper with a hole in the center about 60 percent of the radius of your lens filter.... Place it over the end of the lens and see what happens to the light meter reading.... It drops.....about 1 stop....

This is what happens if you make the lens elements smaller.... It is light from the whole lens surface that gets focused onto the sensor, not just the center part of the lens surface... This is why a 300mm F2.8 lens is the same size no matter what size the sensor is.... Try this yourself if you do not believe me.

A crop sensor does not change the properties of a lens.... What is does is to sample a smaller area of the image circle and thereby reducing the field of view, but at the gain of a higher sampling density. The effect is the same field of view as if the lens was 1.6 times longer. A 300mm lens on a crop sensor would have the same field of view as a 480mm lens on a ff camera would have.... And yes, a 300mm F2.8 lens is a lot smaller and cheaper than a 480mm F 2.8 lens

Sorry Don but I don't think your experiment makes sense. All you are doing is reducing the efficency of the lens.
How about a different approach. Think of a magnifying glass. The smaller you make the images the brighter it becomes. This is the opposite of what we see with converters. They magnify the image so even more photons miss the sensor.

The way I would look at it is that of all the photons that enter a big white a fairly high percentage hit a full frame sensor. Just a few are lost as we use rectangular sensors behind a round lens. But when that sensor is cropped to 1/1.6 of the size then only about 40perecent of the original photons are captured. (that's 1/1.6 squared for the mathematically inclined)
« Last Edit: August 10, 2013, 12:27:52 AM by Skulker »
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schill

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Re: Crop sensors need cropped lenes
« Reply #19 on: August 10, 2013, 12:40:08 AM »
The closest comparison I can find is:

Crop - Sigma 50-150mm DC OS 76 x 135 mm  1340g - $949
FF    - Sigma 70-200mm OS       87 x 184mm  1390g - $1,249

150 to 200 is a pretty big difference.

150 on a 1.5 crop is 225.  on a 1.6 it's 240.
The lens was actually created and marketed as a way to get a similar range on a crop that a 70-200 provides.  If you have some better examples, tell me.

But I don't want the equivalent of a FF 200 on my 7D, I want to use a 70-200/2.8 (real numbers) which gives me an "effective" 320.  A crop specific true 70-200/2.8 will not be much smaller than a FF lens.

rs

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Re: Crop sensors need cropped lenes
« Reply #20 on: August 10, 2013, 03:12:58 AM »
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.
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Sporgon

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Re: Crop sensors need cropped lenes
« Reply #21 on: August 10, 2013, 03:58:41 AM »
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.

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Re: Crop sensors need cropped lenes
« Reply #21 on: August 10, 2013, 03:58:41 AM »

Skulker

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Re: Crop sensors need cropped lenes
« Reply #22 on: August 10, 2013, 04:28:26 AM »
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.
If you debate with a fool onlookers can find it VERY difficult to tell the difference.

rs

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Re: Crop sensors need cropped lenes
« Reply #23 on: August 10, 2013, 05:11:48 AM »
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.
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Sporgon

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Re: Crop sensors need cropped lenes
« Reply #24 on: August 10, 2013, 05:44:40 AM »
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

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Re: Crop sensors need cropped lenes
« Reply #25 on: August 10, 2013, 06:55:54 AM »
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.
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rs

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Re: Crop sensors need cropped lenes
« Reply #26 on: August 10, 2013, 07:20:16 AM »
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
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Pi

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Re: Crop sensors need cropped lenes
« Reply #27 on: August 10, 2013, 10:36:14 AM »
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.

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Re: Crop sensors need cropped lenes
« Reply #27 on: August 10, 2013, 10:36:14 AM »

neuroanatomist

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Re: Crop sensors need cropped lenes
« Reply #28 on: August 10, 2013, 10:55:35 AM »
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. 
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Pi

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Re: Crop sensors need cropped lenes
« Reply #29 on: August 10, 2013, 11:03:42 AM »
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?

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Re: Crop sensors need cropped lenes
« Reply #29 on: August 10, 2013, 11:03:42 AM »