Crop cameras and lenses - crop when?
Mar 17, 2018 13:22:56 #
jaycoffman
Loc: San Diego
OK, I'm now confused (I know--that's easy). We've had lots of discussions here about crop cameras vs. full frame cameras and DX vs FX lenses. Yesterday I went into our local camera store to see about renting a Tamron 18-400 lens for my d7100 (a crop camera). The person there told me that since this lens is a DX lens it's made for a crop camera so there is no multiplication factor when considering the focal length--it will be a max of 400 mm on this lens. And, only if I got a FX lens would the crop factor come into play. It's possible this is true but it surprised me because I've never picked that up from our many [spirited] discussions of crop frame and full frame cameras and DX and FX lenses.
Is what I was told yesterday correct or was the clerk mistaken? (If he is mistaken I have to consider sticking with online suppliers as this will not be the first time this store will have given me spotty information--but if he's correct I do like to work with local stores when possible.)
Is what I was told yesterday correct or was the clerk mistaken? (If he is mistaken I have to consider sticking with online suppliers as this will not be the first time this store will have given me spotty information--but if he's correct I do like to work with local stores when possible.)
Mar 17, 2018 13:32:38 #
jaycoffman wrote:
OK, I'm now confused (I know--that's easy). We've ... (show quote)
Sounds like someone needs a new job. Personally, I would talk to the owner/manager of the store. If their attitude is the same, I would look elsewhere to purchase merchandise, on hand knowledge is the main motivator to buying from a local store as opposed to online. I prefer a local store and think they should be supported when possible, but if they do not care enough to know about the merchandise they are selling, it is time to move on.
Mar 17, 2018 13:36:07 #
jaycoffman wrote:
OK, I'm now confused (I know--that's easy). We've ... (show quote)
No, he is not correct. A 400 mm lenses is a 400 mm lens period.
When on a crop sensor camera you still multiply to get the eqiv. angle of view. In this case the AOV at max zoom is 600 mm.
I use crop sensor and FF cameras. I use the crop sensor with my long lenses for birds etc. The FF for just about everything else. If I am out with the FF I will not pass up a chance at a good bird shot. But when I crop the image to fill the frame with the bird I know it will not have as many pixels on the subject as if I took it with the crop sensor in the first place.
Mar 17, 2018 13:36:51 #
azted
Loc: Las Vegas, NV.
My experience is with Tamron lenses for Sony. The 18-200 lens I bought for my Nex-7 had a focal length of 27 to 300 mm. The crop factor of 1.5 is in the camera sensor, not the lens. The glass is sized for the smaller sensor, making it less expensive, but the focal length is a set parameter. I believe the clerk is not trained well.
Mar 17, 2018 13:38:02 #
If I understand what he was saying, then he was mistaken.
The coverage or MM of the lens is the same whether it's made for a DX or FX sensor is inconsequential.
All the crop factor is telling you is that on a DX camera the coverage of the sensor diagonally would be like using a lens that is 1.5 times longer.
I might not stop using that camera store, but I would speak to the management about training their employees better or hiring people that are already into photography.
The coverage or MM of the lens is the same whether it's made for a DX or FX sensor is inconsequential.
All the crop factor is telling you is that on a DX camera the coverage of the sensor diagonally would be like using a lens that is 1.5 times longer.
I might not stop using that camera store, but I would speak to the management about training their employees better or hiring people that are already into photography.
Mar 17, 2018 13:38:37 #
jaycoffman wrote:
OK, I'm now confused (I know--that's easy). We've ... (show quote)
First of all the focal length does not change. What changes is the angle of view. An 18-400mm lens will remain an 18-400mm lens, but on a DX camera the angle of view will be equivalent to 27-600mm.
Second, whether the lens is of DX or FX design will have no bearing on what the angle of view is. The angle of view is solely reliant on the sensor size.
Mar 17, 2018 13:43:00 #
zug55
Loc: Naivasha, Kenya, and Austin, Texas
FX lenses are constructed to expose the entire sensor on a FX camera. DX cameras have a smaller sensor. So if you put an FX lens on a DX body, the lens sends more information (a larger image) to the sensor than the smaller sensor can accept and record. The smaller sensor only records the center of the image, but not the outer fringes. So the edge of the picture gets cropped away by the smaller sensor, hence the crop factor. The factor between FX and DX is about 1.5. So at 400mm, you get an image as if you had a 600mm lens. Remember, this only happens if you put an FX lens on a DX body. The beauty of this is that your DX sensor still records a 24 MP image--but you de facto have greater magnification. So this is not the same as cropping your image on your computer--there you actually lose megapixels, and the quality of your image decreases. I hope this helps.
Mar 17, 2018 13:43:25 #
jaycoffman
Loc: San Diego
robertjerl wrote:
No, he is not correct. A 400 mm lenses is a 400 m... (show quote)
Thank you--that is how I though I understand it. Since I'm looking for a lens to take to Africa on safari I want one as long as possible but not too heavy as I'm not going on a photo tour. From my past experience the 400mm plus crop factor should be enough but just enough. I'll probably rent the 18-400 from the local shop and shoot at the wild animal park to make sure it works for animals at a distance but will almost certainly buy online.
Mar 17, 2018 13:43:58 #
steve_stoneblossom
Loc: Rhode Island, USA
jaycoffman wrote:
OK, I'm now confused (I know--that's easy). We've ... (show quote)
At the risk of almost certainly adding to your confusion, the only characteristic that is affected by using a lens (any lens) on a crop sensor camera is the effective field of view, which will indeed be roughly equivalent to what you would get from a 27-600 lens on a full frame sensor camera.
Mar 17, 2018 13:46:48 #
jaycoffman
Loc: San Diego
zug55 wrote:
FX lenses are constructed to expose the entire sen... (show quote)
Thank you--this help me see it better.
Mar 17, 2018 13:53:42 #
jpwa
Loc: Inland NorthWest
Mac wrote:
First of all the focal length does not change. What changes is the angle of view. An 18-400mm lens will remain an 18-400mm lens, but on a DX camera the angle of view will be equivalent to 27-600mm.
Second, whether the lens is of DX or FX design will have no bearing on what the angle of view is. The angle of view is solely reliant on the sensor size.
Second, whether the lens is of DX or FX design will have no bearing on what the angle of view is. The angle of view is solely reliant on the sensor size.
Can you describe "angle of view". I don't know what that means exactly.
JP
Mar 17, 2018 13:59:37 #
jpwa wrote:
Can you describe "angle of view". I don't know what that means exactly.
JP
JP
https://en.wikipedia.org/wiki/Angle_of_view
Scroll down to the photos for a visual reference. Then, if you want, go back to the math.
--
Mar 17, 2018 14:05:25 #
jpwa wrote:
Can you describe "angle of view". I don't know what that means exactly.
JP
JP
The longer a lens is the more narrow the area presented to the sensor. The opposite of a shorter, wide angle lens. Because a DX sensor is smaller than a FX sensor the image is trimmed to the smaller sensor resulting to a narrower angle of view equivalent to that of a longer lens on a FX sensor.
Mar 17, 2018 15:10:51 #
LWW
Loc: Banana Republic of America
FX = full frame meaning the sensor is the same size as a 35mm frame from film days.
A DX, or APS-C is a smaller sensor that will shoot through a smaller section of the front element, and hence the term "CROP" comes into play.
True, the lens is a 400mm focal length period, forever and ever amen.
That being said, a 400mm focal length lens on a crop/DX/APS-C sensor will give the same field of view as a 600mm focal length of a full frame/FX sensor.
A DX, or APS-C is a smaller sensor that will shoot through a smaller section of the front element, and hence the term "CROP" comes into play.
True, the lens is a 400mm focal length period, forever and ever amen.
That being said, a 400mm focal length lens on a crop/DX/APS-C sensor will give the same field of view as a 600mm focal length of a full frame/FX sensor.
Mar 17, 2018 16:47:03 #
jaycoffman
Loc: San Diego
Thanks to all the great answers and you reaffirmed that I more or less understand this issue. Now I feel confident in making my lens choices for the future.
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