Full Fame & Cropped sensors

[mandab99]

Hi all you experts out there!
Ok so I am studying lenses at the moment. I own a canon 550D which has a cropped sensor, APS-C. I have 2x EF-S lenses for this camera. My question is- because these lenses are made only for a cropped sensor and can not be used on a full frame camera are the focal lengths the true size?, meaning I dont have to convert via the crop factor? EG- 55mm on full frame = 34.37mm on my camera.
Thanks Guys!!!
Manda

[ricktas]

EF-S lenses will not fit on full frame bodies, but the lens is true to it's rating. A 50 mm lens is a 50 mm kens. Have a read of this to understand why your thinking is wrong:

http://www.ausphotography.net.au/forum/showlibrary.php?title=New_To_Photography:Focal_Length_vs_Crop_Factor

Your field of view changes with a cropped sensor, not the lens length.

[mandab99]

Hi Rick
Thanks for the feedback but I realized I worded my question wrong. What I meant to ask was does my 55mm EF-S lens show the same field of view as a 55mm EF full frame lens or do I have to use the cropped focal length of 34.37mm on my camera to achive the same field of view as the full frame camera acheives using the EF 55mm lens. Does that make sense? Still getting my head around terminology.

[ricktas]

I don't think you are understanding the link I provided. The field of view at 50mm on a cropped sensor camera and a FF camera re different, which is what the graphic in my link shows (compare the field of view of the RED (ff sensor) lines to the dashed (cropped) lines. The cropped sensor doesn't give you the whole tree, cause of the crop effect, at the same focal length.

[selaw]

Hi Rick
Thanks for the feedback but I realized I worded my question wrong. What I meant to ask was does my 55mm EF-S lens show the same field of view as a 55mm EF full frame lens or do I have to use the cropped focal length of 34.37mm on my camera to achive the same field of view as the full frame camera acheives using the EF 55mm lens. Does that make sense? Still getting my head around terminology.


Hi Manda, If I mayy have a go at trying to explain something I have learned through my AP experience. The link posted by Rick is a good one and shows in a picture what we are writing here in a “thousand words”.

55mm EF-S or 55mm EF is still 55mm (all comes from the same "benchmark").

The differences are only in sensor sizes. If they made lenses to reflect their ratings (e.g. 55mm) matched to individual sensors then there would be a whole lot more "specialist" lenses to suit 1.3, 1.5, 1.6, full frame and probably more. Think about third party manufacturers such as Sigma & Tamron, they have lenses (of given focal lengths) for Canon (1.5 crop factor) & Nikon (1.6 crop factor). Although minimal, there is a difference between the two fields of views even though the "build" of the lenses are exactly the same (same 55mm focal length etc).

It is my understanding that, in the digital age, lenses are made to suit and accommodate a multitude of different needs to the age of film. Some lenses markings (EF-S, DX, Di II etc) are suitable (and highly recommended) for cropped sensors alone (APS-C). As Rick indicated, you cant use (physically mount) EF-S lenses on EF mounted cameras. Some lens markings (EF, FX, Di etc) are suitable for full frame and Canon’s 1.3x crop sensor (APS-H). This is where you can work backwards to probably understanding the concept. Lenses suitable for full frame sensors are also able to be mounted and used on the cropped sensor cameras (remember earlier? Can't go from EF-S to EF but can go from EF to EF-S). The sensor now is only able to “see” a part of what the lens wants to show. 55mm on full frame sensor (APS-H 35mm) = 55mm focal length…55mm on a 1.5x cropped sensor (APS-C) = 82.5mm ‘equivalent’ focal length on a full frame sensor, on a 1.6x cropped sensor = 88mm ‘equivalent’ focal length on a full frame sensor. Focal length is benchmarked as in a formulate relationship between sensor plane / film plane & thin air distance.

From this we should be able to see that a lens focal rating (55mm etc) is indiscriminate to application. This is why we have an increase of new ultra wide angle lenses to maximise the use of the smaller sensors used in most of today’s digital cameras.

Please note that my observations are purely as a barely accomplished amature and mostly an interpretation of research. There are plenty of threads on AP dealing with all sorts of issues similar to this one. Spend a bit of time searching the topics of interest particularly in the Library as well as the F&Q headers.

I hope that I have managed not to confuse you too much and if anyone has noticed something I need correcting PLEASE let me know ASAP. It’s all about learning and sharing. Enjoy :)

[mandab99]

The penny has finally dropped!!!!! I swear I am my own worse enemy, always make things more complicated than they really are. And thank you selaw for taking so much of your time and effort to clarify this issue for me:D
Manda

[praet]

Hi there,

I just signed up to this forum. btw it's great!

I own a Canon 1000D DSLR and looking to get a EF 50mm lens. So that means the angle of my field of view is lessened due to the crop factor, is that right?

I looked at the tree image link, and wondered how it would be possible to get the same field of view of the 35mm camera in that link. Is it a matter of just standing further back? Or using a zoom lens (say 18-55mm) and go 50/1.6 = focal length on lens ?

I'm sorry if that's confusing, only because I'mconfused myself :eek:

Here's another way of explaining question:

Person A: 35mm FF SLR, 50mm lens
Person B: Canon APS-C sensor, 50mm lens, 18-55mm lens

In relation to the tree link, how could person B obtain the same angle of FOV as Person A? Or am I asking the impossible? :eek:

Cheers
Julz

[Speedway]

A simple way is just multiply the focal length by 1.6 for Canon crop sensor or 1.5 for Nikon ie. 50mm X 1.6 = 80mm or X 1.5 =75mm, 30mm X 1.6 = 48mm, or X 1.5 = 45mm. The lens size dosent alter only the sensor size so the crop sensor only sees part of the image giving the same result as cropping a full frame picture X 1.5 or 1.6.
Keith.

[praet]

A simple way is just multiply the focal length by 1.6 for Canon crop sensor or 1.5 for Nikon ie. 50mm X 1.6 = 80mm or X 1.5 =75mm, 30mm X 1.6 = 48mm, or X 1.5 = 45mm. The lens size dosent alter only the sensor size so the crop sensor only sees part of the image giving the same result as cropping a full frame picture X 1.5 or 1.6.
Keith.

Thanks Keith.
In regards to the 50mm x 1.6 = 80mm example, would it be as simple as fitting a zoom lens and adjusting focal length to approx 30mm?

So by changing my zoom to approx. 30mm (as I imagine trying to get exactly 31.25mm is difficult) would this give me the same angle of field of view when compared to a 50mm lens on a 35mm FF camera?

I'm sorry for my confusion :(

-Julz

[Kym]

I have (amoung others) two prime lenses.

A 50mm f/1.7 and a 35mm f/2.4.

If I put the 50mm on my MX (35mm film) and the 35mm on my K-5 (APS-C 1.5 so 52.5mm equivalent) I get (more or less) the same result, albeit the perspective differs slightly.

[praet]

I have (amoung others) two prime lenses.

A 50mm f/1.7 and a 35mm f/2.4.

If I put the 50mm on my MX (35mm film) and the 35mm on my K-5 (APS-C 1.5 so 52.5mm equivalent) I get (more or less) the same result, albeit the perspective differs slightly.

Hi Kym, Thanks for replying. I understand your post, but unclear what you mean the perspective differs slightly.

Do you have any links that displays two photographs side by side to show the difference? I realise there is a link from an earlier post, but I just need to see actual photographs to make sense of the concept :)

Cheers
Julz

[Kym]

This http://www.ausphotography.net.au/forum/showlibrary.php?title=New_To_Photography:Full_Frame_vs_APS-C_DX_crop_factor_w_example

But in the end, it really matters little in practice. I don't think about it when shooting, just frame the shot with the lens you selected and squeeze the shutter. The numbers don't really matter

[selaw]

Thanks Keith.
In regards to the 50mm x 1.6 = 80mm example, would it be as simple as fitting a zoom lens and adjusting focal length to approx 30mm?

So by changing my zoom to approx. 30mm (as I imagine trying to get exactly 31.25mm is difficult) would this give me the same angle of field of view when compared to a 50mm lens on a 35mm FF camera?

I'm sorry for my confusion :(

-Julz

Hi Julz & welcome to AP. I think you have pretty much understood it here. Your willingness to understand shows a keen interest in the myriad of photgraphical conundrum. This is healthy however not quite so suggestive as a main course for fear of "technical indigestion" . I can only suggest not to get too caught up in it all because a whole lot of other issues can pop up like the relationship between the DOF & f/stop comparisons with subject distance & image compression. Kym has a good point, just frame the shot with whatever you are using and take the photo. Technical aspects can become a complex. We just want to see your great photos :)

[praet]

This http://www.ausphotography.net.au/forum/showlibrary.php?title=New_To_Photography:Full_Frame_vs_APS-C_DX_crop_factor_w_example

But in the end, it really matters little in practice. I don't think about it when shooting, just frame the shot with the lens you selected and squeeze the shutter. The numbers don't really matter

Okay, sounds good to me! LOL

I thought it somehow mattered in photography, where exactly I don't know, hence my crazy questions :P

But if I frame a great shot then the technical mumbo jumbo I was trying to suss doesn't really matter hey.

I'm just someone who likes to know how things work, and sometimes I am my own worst enemy!

Cheers

[ricktas]

rather that worry about what a crop or FF sensor camera can do, go out with what you have and learn to take photos. After all, no use lamenting not having a FF camera, that doesn't help in any way. Use the gear you have, which can take amazingly good photos, if the person using the camera knows what they are doing. Learn your craft, learn your gear and forget about the "what if's"

[praet]

Hi Julz & welcome to AP. I think you have pretty much understood it here. Your willingness to understand shows a keen interest in the myriad of photgraphical conundrum. This is healthy however not quite so suggestive as a main course for fear of "technical indigestion" . I can only suggest not to get too caught up in it all because a whole lot of other issues can pop up like the relationship between the DOF & f/stop comparisons with subject distance & image compression. Kym has a good point, just frame the shot with whatever you are using and take the photo. Technical aspects can become a complex. We just want to see your great photos :)

Ah thanks mate :) Yep, I am pretty keen to understand how it all works, but from what I hear, I shouldn't let technical hoo-ha get in the way of taking a great shot :th3:

Cheers!
Julz

[praet]

rather that worry about what a crop or FF sensor camera can do, go out with what you have and learn to take photos. After all, no use lamenting not having a FF camera, that doesn't help in any way. Use the gear you have, which can take amazingly good photos, if the person using the camera knows what they are doing. Learn your craft, learn your gear and forget about the "what if's"

Will do! At the moment the camera is much more advanced than I am, but hope to change all that with plenty of learning. Cheers!