35mm Equivalent on Crop Sensor - DX vs FX Lenses

[Designer]

So when he says "35mm look" what's he referring to, what he sees on the viewfinder or picture itself?

Both, actually. They should be nearly the same image.

As for me, I would recommend some other prime lens rather than either the 35mm or 50mm. Something longer would be my first choice. So many nice lenses available, that it is hard to pick just one.

What kind of photography do you like to do? The 35 might be nice for an all-purpose carry-around lens. For portraiture, you should use something longer, with a good minimum focal length being 85mm, and going up from there, such as; 105, 135, 180, etc.

 

[greybeard]

It is easy to get confused with this. The 1.5 crop factor means that a 100mm FF lens on crop frame will have the same Field of View as a 150mm lens on a full frame camera. The focal length doesn't change it is the size of the sensor that captures the image that makes this all happen. Because the crop frame sensor is about 1/2 the size of a Full frame sensor it only captures the image coming from the center part of the lens whereas the FF sensor is big enough to capture the entire image. There are, of course, lenses made specifically for crop frame cameras. Nikon specifies these as DX as opposed to FX for full frame. Crop frame lenses mounted on a FF camera will NOT produce an image that will cover the entire sensor.

 

[AlexGavillan]

IMHO it is the wider FoV. If your back is up against the wall with a 50mm lens, you cannot backup any more to get a wider FoV. Hence the 35.
This is why when I shot 35mm film, I used a 24mm lens. I did not always need that wide a coverage, but when I did, I did. And the wider the better. But because the 24 is so wide, I did not use it as my only lens. I always used it in conjunction with another narrower lens. Whereas a 35 could be used as the only lens.

He is also considering how the background and out of focus blur looks.

Totally, and now I understand that haha. I'm a fairly quick learner, but there are some things where im like huh...1 more time haha .

So when he says "35mm look" what's he referring to, what he sees on the viewfinder or picture itself?

Both, actually. They should be nearly the same image.

As for me, I would recommend some other prime lens rather than either the 35mm or 50mm. Something longer would be my first choice. So many nice lenses available, that it is hard to pick just one.

What kind of photography do you like to do? The 35 might be nice for an all-purpose carry-around lens. For portraiture, you should use something longer, with a good minimum focal length being 85mm, and going up from there, such as; 105, 135, 180, etc.

I picked up the NIKKOR 35mm 1.8G DX and it works great for what I'm doing. Walk abouts and just random pictures here and there. Street photography and "things" if you will really draw my interest. I'm a hobbiest, but I alos like to learn, so just buying a DSLR, kit lens and shooting in auto didn't cut it for me. I wanted to learn about exposure, different metering modes, etc. Im an enfiengi by trade, so I can't help it haha.

It is easy to get confused with this. The 1.5 crop factor means that a 100mm FF lens on crop frame will have the same Field of View as a 150mm lens on a full frame camera. The focal length doesn't change it is the size of the sensor that captures the image that makes this all happen. Because the crop frame sensor is about 1/2 the size of a Full frame sensor it only captures the image coming from the center part of the lens whereas the FF sensor is big enough to capture the entire image. There are, of course, lenses made specifically for crop frame cameras. Nikon specifies these as DX as opposed to FX for full frame. Crop frame lenses mounted on a FF camera will produce an image that will cover the entire sensor.

Thanks. Ya I looked that up a ehioe back DX vs FF or just not notaded as DX. I would like a lenses with more reach, like an 85mm for portraits and what not right now just have a faster lens than tye kit lens has been an awesome treat. Now I'm looking into not shooting everything wide open, finding the sweet spot for this lense. So far I love everything I'm learning.

 

[ac12]

quote

I picked up the NIKKOR 35mm 1.8G DX​

end quote

Just realize that a 35mm is a "normal" lens on your DX camera, not a wide.
A "normal" lens is just fine. On my 35mm film camera, I used a 50mm normal for several years before switching to a 43-86 short zoom.

Nikon unfortunately does not make a 24mm DX wide lens. You have to buy the more expensive FX 24mm lens. Then you have to be careful which one you get, based on which camera you have. Your D3400 cannot autofocus an AF or AF-D lens, because it does not have an AF motor in the body.

 

[KB2]

Example, if I want a 105mm lens that's DX there is still a 1.5 crop factor which really gives me the focal length of a 155mm.

This is incorrect. With a DX camera and a DX lens, there is no crop factor. A 105mm DX lens will act as a 105mm lens on your DX camera. If you end up buying a full frame camera later, that lens will give you a bad vignette that needs to be cropped, and that can be done automatically by your camera. When I "upgraded" to a FX camera, I got rid of my DX lenses. That being said, if you buy FX lenses now for your DX camera you will want to take the crop factor into account. For example, I've always had a 50mm FX lens, and on my DX camera I never felt like I could back up far enough in my house to take pictures of my kids, but now that it's on a FX camera I don't have that problem.

 

[BrentC]

Example, if I want a 105mm lens that's DX there is still a 1.5 crop factor which really gives me the focal length of a 155mm.

This is incorrect. With a DX camera and a DX lens, there is no crop factor. A 105mm DX lens will act as a 105mm lens on your DX camera. If you end up buying a full frame camera later, that lens will give you a bad vignette that needs to be cropped, and that can be done automatically by your camera. When I "upgraded" to a FX camera, I got rid of my DX lenses. That being said, if you buy FX lenses now for your DX camera you will want to take the crop factor into account. For example, I've always had a 50mm FX lens, and on my DX camera I never felt like I could back up far enough in my house to take pictures of my kids, but now that it's on a FX camera I don't have that problem.

No this is incorrect. Once again Focal length is focal length is focal length. What is stated on the lens is the focal length of the lens which is a physical measurement. 105mm DX lens is the exact same focal length as a 105mm FX lens. And yes a 105mm DX lens will have the same FoV as a 155mm lens on a DX camera.

 

[KB2]

Example, if I want a 105mm lens that's DX there is still a 1.5 crop factor which really gives me the focal length of a 155mm.

This is incorrect. With a DX camera and a DX lens, there is no crop factor. A 105mm DX lens will act as a 105mm lens on your DX camera. If you end up buying a full frame camera later, that lens will give you a bad vignette that needs to be cropped, and that can be done automatically by your camera. When I "upgraded" to a FX camera, I got rid of my DX lenses. That being said, if you buy FX lenses now for your DX camera you will want to take the crop factor into account. For example, I've always had a 50mm FX lens, and on my DX camera I never felt like I could back up far enough in my house to take pictures of my kids, but now that it's on a FX camera I don't have that problem.

No this is incorrect. Once again Focal length is focal length is focal length. What is stated on the lens is the focal length of the lens which is a physical measurement. 105mm DX lens is the exact same focal length as a 105mm FX lens. And yes a 105mm DX lens will have the same FoV as a 155mm lens on a DX camera.

Very sorry, I'm fairly new at this too, and what I said has been my understanding for a long time. Should have kept my mouth shut. Maybe my description of using both types of lenses on both types of camera bodies will be of some use...

 

[480sparky]

Let's put this to rest.

A 50mm lens is............. fifty millimeters. The glass inside a lens does not 'know' what format camera is behind it. A 50mm full-frame lens doesn't go, "Oh, there's a crop sensor back there. I'd better magically transform into a 75mm!" Because one of two things would have to happen if it did. One, it would have become longer. It would have to physically move away from the camera an additional 25mm. This means your 50mm lens would become about an inch longer. If it didn't the second option would occur.... you'd never be able to focus the lens.


It doesn't matter if it's a µ4/3, crop sensor, full frame sensor, 6x4.5, 6x6, 6x7 or even 4x5. It can be an obsolete 110-, 122- or 126-based film camera.


Think of it this way: You take a photo with a 50mm lens and have an 8x10 print made. You now take a pair of scissors and cut out the center of the 8x10, and end up with a 6x7 photo. Did that change anything about the lens you used? No. It was still taken with a 50mm. Just because you lopped off the outer parts of the image didn't change that one bit.

Same principle for crop v full-frame sensors. Crop sensors do the same thing to the projected image in a camera as your pair of scissors did to the print.... it just recorded a smaller area.

 

[AlexGavillan]

Example, if I want a 105mm lens that's DX there is still a 1.5 crop factor which really gives me the focal length of a 155mm.

This is incorrect. With a DX camera and a DX lens, there is no crop factor. A 105mm DX lens will act as a 105mm lens on your DX camera. If you end up buying a full frame camera later, that lens will give you a bad vignette that needs to be cropped, and that can be done automatically by your camera. When I "upgraded" to a FX camera, I got rid of my DX lenses. That being said, if you buy FX lenses now for your DX camera you will want to take the crop factor into account. For example, I've always had a 50mm FX lens, and on my DX camera I never felt like I could back up far enough in my house to take pictures of my kids, but now that it's on a FX camera I don't have that problem.

I was getting focal length and field of view confused. I know that the focal length doesn't change, that is something physical, I guess where I was confused was in the "35mm equivalent" they are reffering to the FoV? I swear I will get this So the 50MM on your DX was giving you the FoV of a 75mm lens, really hope I got that right

Example, if I want a 105mm lens that's DX there is still a 1.5 crop factor which really gives me the focal length of a 155mm.

This is incorrect. With a DX camera and a DX lens, there is no crop factor. A 105mm DX lens will act as a 105mm lens on your DX camera. If you end up buying a full frame camera later, that lens will give you a bad vignette that needs to be cropped, and that can be done automatically by your camera. When I "upgraded" to a FX camera, I got rid of my DX lenses. That being said, if you buy FX lenses now for your DX camera you will want to take the crop factor into account. For example, I've always had a 50mm FX lens, and on my DX camera I never felt like I could back up far enough in my house to take pictures of my kids, but now that it's on a FX camera I don't have that problem.

Thanks, I didnt know that there was NOT a crop factor with DX lenses. I assumed again because they sat "35mm equivalent" that that meant its times the 1.5 crop. And you're 100% right, I looked (Trust but verifiy) and it does NOT say anything on Nikons site about 35mm equivalent on the DX lens. But on BnH photo it does... Again, that's why i have been getting SO confused.

BnH: Nikon 35mm f/1.8G AF-S DX Nikkor Lens 2183 B&H Photo

No this is incorrect. Once again Focal length is focal length is focal length. What is stated on the lens is the focal length of the lens which is a physical measurement. 105mm DX lens is the exact same focal length as a 105mm FX lens. And yes a 105mm DX lens will have the same FoV as a 155mm lens on a DX camera.

GOT IT!!! HAHA Focal length and Field of View, thats what was getting me.

Let's put this to rest.

A 50mm lens is............. fifty millimeters. The glass inside a lens does not 'know' what format camera is behind it. A 50mm full-frame lens doesn't go, "Oh, there's a crop sensor back there. I'd better magically transform into a 75mm!" Because one of two things would have to happen if it did. One, it would have become longer. It would have to physically move away from the camera an additional 25mm. This means your 50mm lens would become about an inch longer. If it didn't the second option would occur.... you'd never be able to focus the lens.


It doesn't matter if it's a µ4/3, crop sensor, full frame sensor, 6x4.5, 6x6, 6x7 or even 4x5. It can be an obsolete 110-, 122- or 126-based film camera.


Think of it this way: You take a photo with a 50mm lens and have an 8x10 print made. You now take a pair of scissors and cut out the center of the 8x10, and end up with a 6x7 photo. Did that change anything about the lens you used? No. It was still taken with a 50mm. Just because you lopped off the outer parts of the image didn't change that one bit.

Same principle for crop v full-frame sensors. Crop sensors do the same thing to the projected image in a camera as your pair of scissors did to the print.... it just recorded a smaller area.

Ya, now knowing about FoV all of this makes sense. Hopefully what I wrote above makes sense and I am getting this ingrained in my brain!

 

[ac12]

Quote

So the 50MM on your DX was giving you the FoV of a 75mm lens ...​

correction

The 50mm lens on a DX camera gives you a similar FoV to a 75mm lens on a FX camera.
Or more clearly:
The FoV of a 50mm lens on a DX camera is similar to the FoV of a 75mm lens on a FX camera.
​

You MUST state what platform the lens is on, or it makes no sense.
This is because FoV is dependent on both focal length and sensor size.

 

[AlexGavillan]

Quote

So the 50MM on your DX was giving you the FoV of a 75mm lens ...​

correction

The 50mm lens on a DX camera gives you a similar FoV to a 75mm lens on a FX camera.
Or more clearly:
The FoV of a 50mm lens on a DX camera is similar to the FoV of a 75mm lens on a FX camera.
​

You MUST state what platform the lens is on, or it makes no sense.
This is because FoV is dependent on both focal length and sensor size.

Got it!

 

[ac12]

I still prefer magnification, as it gets away from all this confusing "equivalent focal length" stuff.
And that is how I work.

m4/3: 25mm normal lens (1x), 2x = 50mm, 0.5x = 12mm
DX: 35mm normal lens, 2x = 70mm, 0.5x = 17mm
35mm/FF/FX: 50mm normal lens, 2x = 100mm, 0.5x = 25mm
6x6: 80mm normal lens, 2x = 160mm, 0.5x = 40mm
4x5: 150mm normal lens, 2x = 300mm, 0.5x = 75mm

When I got my tele for the 6x6, I did not do an equivalent focal length. I did a 2x on my 80mm normal lens to get to 160, then selected the closest lens to 160, which was 150mm.

You NEED to think in the format that you are shooting, or this lens math will drive you nuts.

 

[AlexGavillan]

LOL looks like this has been a discussion for a long time.

What does "..equivalent to 52.5mm in 35mm format" mean? - PentaxForums.com

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