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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 04 Mar 2015 (Wednesday) 04:11
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EF lens aperture question

 
muhsal
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Mar 04, 2015 04:11 |  #1

Hello

If I use an EF lens on my crop sensor camera body, does the aperture also gets multiplied by the crop factor? For example if i use the 50mm EF f1.4, would it be as if i am using a f2.2 lens?

Thanks (from a novice)




  
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Mar 04, 2015 04:51 |  #2

No,, the aperture will always be f/1.4 irrespective of a FF or crop sensor.


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Mar 04, 2015 05:35 |  #3

From the standpoint of metering and exposure, there is no difference. So if a shot is properly exposed at ISO 100, 1/1000 and f/1.4 on a FF camera, it will be properly exposed with the same settings (including aperture) on a smaller format camera.

The only place you might thing of the format having an effect on how aperture works is in the depth of field. Suppose you and I were trying to take the exact same picture from the exact same location. You place your 1.6X format camera on a tripod and take a picture at 35mm and f/1.4.

To take the same picture from the tripod with my FF format camera I need to use a longer focal length (35mm x 1.6 = 56mm). And since I'm using a longer focal length lens I also need to stop down a bit (1 and 1/3 stops) to get the same depth of field. So I should shoot the same picture from a FF camera at 56mm and f/2.2. I would have to compensate the light loss in stopping down by either increasing the ISO or decreasing the shutter speed.


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SkipD
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Mar 04, 2015 06:31 |  #4

muhsal wrote in post #17459833 (external link)
If I use an EF lens on my crop sensor camera body, does the aperture also gets multiplied by the crop factor? For example if i use the 50mm EF f1.4, would it be as if i am using a f2.2 lens?

The specific question has been answered above (the answer is NO), but I'd like to ask you a question.

Do you use or have experience with 35mm film cameras or so-called "full-frame" DSLRs?

If the answer to my question is no, then you have very little reason to consider doing any "crop factor" math at all. The focal lengths of your lenses DO NOT CHANGE when you use them on a so-called "crop sensor body". The "crop factor" math has only one purpose - comparing field (angle) of view for a given focal length between two different camera formats (format refers to the physical size of the film frame or sensor in a camera).

If you need more info about the "crop factor" stuff, just ask.....


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muhsal
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Mar 04, 2015 10:22 as a reply to  @ SkipD's post |  #5

thanks a lot for the explanation. I don't use a full frame body. I wasn't really concerned about the equivalent focal length, but just that if an EF lens says f1.4 and EF-S lens says f1.4 will there will be any difference of aperture on a crop body. Now it seems it wont have any.




  
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Mar 04, 2015 11:48 |  #6

muhsal wrote in post #17460239 (external link)
thanks a lot for the explanation. I don't use a full frame body. I wasn't really concerned about the equivalent focal length, but just that if an EF lens says f1.4 and EF-S lens says f1.4 will there will be any difference of aperture on a crop body. Now it seems it wont have any.

The marked focal lengths and marked maximum aperture values on camera lenses are what they are regardless of the design of the lens.

That said, folks have found that sometimes the marked focal lengths on two different lenses are a little different from each other. This is due to two reasons.

  • One reason is that almost all camera lenses' focal lengths are stated as being valid when the lens is focused at infinity and folks may be testing field of view of two same-focal-length lenses when focused much closer that "infinity".
  • The other reason is that manufacturers often round the focal length values, probably for marketing reasons. For example, if someone made a lens that was actually a 97mm focal length lens, it would probably be marketed as 100mm. A zoom lens that was actually 72mm to 195mm would probably be marketed as 70-200mm.

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Post edited over 4 years ago by Wilt. (7 edits in all)
     
Mar 04, 2015 13:01 |  #7

The world would be better served if it got rid of all discussions of 'crop factor' calculations, as all it does is screw up people's heads.

The only person who EVER is served by the calculation is only someone who has extensively shot the 135/FF format size with lenses of a particular known FL...as he/she can then calculate
the different FL needed to achieve the same Angle of View to be captured with a smaller Canon size (APS-C) sensor.

For any other shooters, there is absolutely no beneficial relevance of ANY calculation based upon some multiplier value. The crop factor multiplier probably last had any real purpose or value about 5-10 years ago, as most veteran film SLR shooters probably had already purchased an APS-C digital SLR by then. 135 format P&S shooters never knew what FL they ever shot at (apart from knowing 'widest FL' or 'longest FL' status but not ever the numerical value of FL which was set.


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Mar 04, 2015 14:01 |  #8

Wilt wrote in post #17460474 (external link)
The world would be better served if it got rid of all discussions of 'crop factor' calculations, as all it does is screw up people's heads.

The only person who EVER is served by the calculation is only someone who has extensively shot the 135/FF format size with lenses of a particular known FL...as he/she can then calculate
the different FL needed to achieve the same Angle of View to be captured with a smaller Canon size (APS-C) sensor.

For any other shooters, there is absolutely no beneficial relevance of ANY calculation based upon some multiplier value.

Wilt,

Almost everything I've ever read from you is extremely accurate, and I have always held your posts in high regard. But this time I disagree with you.

I photograph wildlife. A good deal of my photography is done from blinds (called "hides" in the UK). Very often, a blind is constructed near a key location, such as a bird's nest or a place from which they perform a mating display, like a Ruffed Grouse's drumming log. In such situations, the camera-to-subject distance is fixed; the blind is left in place for weeks, or even months. The birds eventually get used to it, and lose their fear of it. So I don't move the blind, as that would alarm the birds and cause them to "abandon their post", so to speak.

Often times, there are hideous eyesores around the site - tangled masses of wayward vegetation, bleached bark that produces harsh glare, build-up of bird poop, etc. So, my point here is that certain compositions are preferable, and attempts to compose differently are often unsuccessful, as the camera position is fixed and one has to shoot from one given angle. Hence, a given field of view is perfectly fitted to the scene. Shoot wider, and you are just wasting pixels and missing out on feather detail because you'll have to crop out all of the crappy looking stuff around the edges of the frame. Shoot tighter, and the result will most likely be a composition that is awkward looking because it is too tight. Often, tighter compositions will not even enable one to fit the entire bird in the frame.

The precise location of the blind is based on creating what I believe is the best composition with my preferred focal length, as it appears on my 1.3 crop body. The focal length I used on one such situation was 400mm + 1.4 extender to arrive at 560mm. That is 560mm on my 1.3 crop body.

Now, what happens when other photographers - friends of mine - come to shoot from my blind?

One such friend shoots Nikon, and has a body with a 1.5 crop sensor. And a 500mm lens. And a 1.4 extender.

Another friend shoots Canon, like me. But, unlike me, he uses a full frame body and a 1.6 crop body. He has a 100-400mm zoom, as well as a 300mm f2.8. And a 1.4 tele-extender.

Another friend also shoots a Canon 1.3 crop body like I do, but he has different lenses than I, and does not have anything that is 400mm. His lenses are a 300mm f2.8, a 500mm lens, and an 800mm lens. He also has the 1.4 extender. But, in addition to the 1.3 crop body, he also has a couple of full frame bodies and a couple of 1.6 crop bodies.

When these guys call me to make arrangements to use a blind, they all ask what equivalent focal length I am shooting to get the images I am getting. They need to know which body to take, and which lens to take, and whether or not to plan on using an extender or not. The calculations you seem to think are so useless are actually very important, as they ensure that the photographers will have the gear best suited to exactly the images they want to take. When taking days off of work and traveling hundreds of miles to photograph a bird, they sure on't want to have to settle for less-than-perfect compositions.

Sometimes, they do the math and realize that what they have won't give them exactly the field of view they want, so they buy another body before the trip, or they rent a lens for the trip. They really need the "equivalent focal length" calculations in order to know what gear to rent or buy.

In any case, the calculations are very important, as they help numerous photographers with sundry gear combinations get precisely the images they want. A photographer may only ever use one sensor size, but he/she will often need to match field of view as closely as possible with another photographer's (different) sensor size. Hence, you have a situation in which the calculations are relevant to one who shoots crop, but has never shot full frame.


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Mar 04, 2015 14:34 |  #9

I agree with the opinions that neither focal length nor aperture of the lens change when you put it on a different camera. I also agree that you should just forget about crop factors.

But next time you are shopping for a lens, consider that there are advantages to buying one that is intended for the format of the body. This will usually save money, bulk and weight.


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Mar 04, 2015 14:50 |  #10

Wilt wrote in post #17460474 (external link)
The only person who EVER is served by the calculation is only someone who has extensively shot the 135/FF format size with lenses of a particular known FL...as he/she can then calculate
the different FL needed to achieve the same Angle of View to be captured with a smaller Canon size (APS-C) sensor.

For any other shooters, there is absolutely no beneficial relevance of ANY calculation based upon some multiplier value. The crop factor multiplier probably last had any real purpose or value about 5-10 years ago, as most veteran film SLR shooters probably had already purchased an APS-C digital SLR by then. 135 format P&S shooters never knew what FL they ever shot at (apart from knowing 'widest FL' or 'longest FL' status but not ever the numerical value of FL which was set.

I do agree that those who buy APS-C DSLRs are more confused than helped, when it comes to crop factor, and would generally be best served just learning how focal length relates to their camera, rather than doing calculations as to how it would relate to a camera they don't have.

But I disagree that it is only those who have used 35mm/FF who can benefit from it. What abvout people looking to buy a point and shoot or bridge camera with a fixed zoom lens. There are many sensor sizes out there and if they all quoted just the actual FL then they would be very hard to compare, when one may have a 2.6x crop factor, another a 3.2 another a 4x etc. You may see one has a 6-36mm lens and another has a 9-55mm lens, which one shoots wider, or longer? By quoting crop factors and "35mm equivalent" FLs they can be compared and it may be the camera with the 9-55 lens is wider angle than the 6-36 because the camera has a bigger sensor.

Also, what if you watch a video on portrait photography and the presenter recommends a 135mm FL for a particular type of shot. You know they use FF, but you use a crop, what FL do you need to use instead?

I do believe that the APS-C users need better information than some are clearly getting from somewhere of course, as many have some very wrong ideas about it.




  
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Wilt
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Mar 04, 2015 15:22 as a reply to  @ Tom Reichner's post |  #11

Tom,

Ask yourself this...


  1. Are you really doing your Nikon friend any favor by doing the arithmetic, given that he owns 500mm and could have 700mm (with telextender) but he needs to have 430mm (which he does not own) to capture precisely the same framing as you? His is a tighter view than yours. Now what?
  2. Are you doing any favor for your friend who shoots a Canon 1.3 crop body and does not have anything that is 560mm (he has 300 or 500mm or 800mm). He has what he has... and can use 500mm but does not 'get the same framing as you' with that lens. His is a wider view than yours by about 10%. Now what?!
  3. Are you doing any favor for your FF friend who has 500mm and 800mm, but needs to use 728mm to get 'get the same framing as you'?! His choice is 32% wider or 10% tighter than yours. Now what?


So you did the crop factor calculations, but it does nothing to get the same framing as you for any of the three friends!
You could tell each of them, "Bring a lens which provides 3.5 degree diagonal field of view", regardless of the specifics of the actual format size they wish to bring. With a AOV calculator they will know precisely that they do not own an equivalent lens as you. Same end result as the three episodes noted above, with the arithmetic that does nothing to alter reality. Yes, they could rent a lens which provides 3.5 degree diagonal angle of view, with no arithmetic to convert between formats.

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Mar 04, 2015 15:37 |  #12

sandpiper wrote in post #17460608 (external link)
But I disagree that it is only those who have used 35mm/FF who can benefit from it. What abvout people looking to buy a point and shoot or bridge camera with a fixed zoom lens. There are many sensor sizes out there and if they all quoted just the actual FL then they would be very hard to compare, when one may have a 2.6x crop factor, another a 3.2 another a 4x etc. You may see one has a 6-36mm lens and another has a 9-55mm lens, which one shoots wider, or longer? By quoting crop factors and "35mm equivalent" FLs they can be compared and it may be the camera with the 9-55 lens is wider angle than the 6-36 because the camera has a bigger sensor..

The only thing they need to know is the '35mm equivalent' so they can see that the 28-105mm equivalent on one camera is not as large a range of FL as your 28-300mm. the crop factor tells that Sensor B is smaller than Sensor A by a certain amount...that is made unnecessary by the '35mm equivalent' statement of FL range of the lens on the body...it matters not that the body with 10mm sensor has 1/2.3 crop factor or the body with 7.5mm sensor has 1/3.2 crop factor! The actual numeric value of the 'crop factor' is rendered pointless, it does not get used.


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Mar 04, 2015 15:40 |  #13

I'm sure the OP is hanging on every word here... ;-)a


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Mar 04, 2015 16:30 |  #14

muhsal wrote in post #17459833 (external link)
Hello

If I use an EF lens on my crop sensor camera body, does the aperture also gets multiplied by the crop factor? For example if i use the 50mm EF f1.4, would it be as if i am using a f2.2 lens?

Thanks (from a novice)

Although the aperture does not change, it so happens that an f/1.4 lens on a full frame camera has about the same depth of field as an f/2.2 lens on a crop. This might be mathematical nonsense, but it works (approximately).

So it behaves like 1.4 for light transmission, but like 2.2 for DOF.


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Mar 04, 2015 16:47 as a reply to  @ Archibald's post |  #15

If you use FL which is appropriate for the format size, e.g. 50mm on APS-C vs. 80mm on FF, to get the same FOV at the same camera position...

you need to use an aperture which is 1.6EV smaller on the FF than on the APS-C


  • 50mm f/2 at 240" subject distance yields 15.47" of DOF zone on APS-C in a framed area of 71" x 106"

  • 80mm f/2 at 240" subject distance yields 9.61" of DOF zone on FF in a framed area of 71" x 106"
    80mm f/2.8 at 240" subject distance yields 13.5" of DOF zone on FF in a framed area of 71" x 106"
    80mm f/4 at 240" subject distance yields 19.25" of DOF zone on FF in a framed area of 71" x 106"

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