Question about Full vs Crop Sensor Cameras

[Ema]

I have a Nikon D7100. Saw sever videos on how 85mm prime is the best lens for portrait photography. Even if I buy a DX lens, it really is not 85mm on a D7100 - correct? It'll be 85mm times 1.5 focal length. So should I be buying a 55mm (56mm to be accurate) to get the effect of a 85mm.
In other words, the crop factor still applies to a DX lens right?
Thanks

 

[Derrel]

Yes the field of view Factor applies to both regular lenses and to DX lenses. For example, on a full frame camera and 85 mm lens is an 85 mm short telephoto. If you put the same focal length of lens on the Nikon D 7100, you multiply the focal length 85 mm times 1.53and you arrive at something around 127 mm in terms of "effective focal length"as it relates to a full frame camera. So in other words on full frame any 85 mm lens is a short telephoto ; on a DX sensor camera,a lens that is 85 mm in length is more or less a medium length telephoto.

As you might have noticed,the Nikon company has an 85 mm macro lens that is DX, and also makes two or three 85 mm lenses that were designed for full frame cameras.

 

[Derrel]

Yes the field of view Factor applies to both regular lenses and to DX lenses. For example, on a full frame camera and 85 mm lens is an 85 mm short telephoto. If you put the same focal length of lens on the Nikon D 7100, you multiply the focal length 85 mm times 1.53and you arrive at something around 127 mm in terms of "effective focal length"as it relates to a full frame camera. So in other words on full frame any 85 mm lens is a short telephoto ; on a DX sensor camera,a lens that is 85 mm in length is more or less a medium length telephoto.

As you might have noticed,the Nikon company has an 85 mm macro lens that is DX, and also makes two or three 85 mm lenses that were designed for full frame cameras.

If you would like to have a lens that performs similarly to an 85 mm lens on a full frame camera, then yes look for a lens from 50 to 58 mm in length. Nikon has a nice new 58 millimeter autofocusing lens,but it is fairly expensive. Most people will press a 50 mm lens into service, but with the 1.53X Field of view factor,A lens of that focal length will perform more like a 75 mm lens.

 

[Derrel]

I would disagree with the idea that a lens of 85 mm in length is "the best" for
Portrait work. I prefer a 105 mm lens to an 85 mm almost all the time, and I found that the 135 mm to 180 mm prime lenses were good, over the years there have been many zoom lenses which are really good for portraiture. One Lens was the 50-135 mm f/3.5 Nikon AIS, as well as many 70-200 mm zoom lenses or 80-200 mm Zoom lenses, as well as the 75-150 mm f/3.5 Series E zoom lens. The idea that the 85 mm lens is "the best" is really quite an oversimplification and is in my opinion an outright untruth.

 

[480sparky]

I recall reading an article years ago about a portrait photographer that didn't use anything shorter than 300mm.

 

[Ema]

Thank you!! Is it better to buy an FX lens, since there is always a path to upgrading the camera to a full frame one down the road. Seems like investing in a DX lens means sticking with D7100 for the future.

 

[Derrel]

I remember the author of a book called how to photograph women beautifully. He used to shoot a lot of advertising photos with the old Nikon 500 mm F5 reflex Lens . This lens was replaced by two different series of 500 mm F/8 lenses beginning around 1973

There is much to be said for using a lens of 300 mm to isolate a person from their environment.

In my opinion the 85 mm lens does not give the ideal compression effect on the face and tends to make the nose appear a little bit larger than I consider ideal. If you look very carefully at lens focal length comparisons where they move the camera farther and farther away as the lens gets longer, you will see as the lens focal length gets longer, the face looks more idealized, a little bit "flatter".

 

[TreeofLifeStairs]

I remember the author of a book called how to photograph women beautifully. He used to shoot a lot of advertising photos with the old Nikon 500 mm F5 reflex Lens . This lens was replaced by two different series of 500 mm F/7 lenses beginning around 1973

There is much to be said for using a lens of 300 mm to isolate a person from their environment.

In my opinion the 85 mm lens does not give the ideal compression effect on the face and tends to make the nose appear a little bit larger than I consider ideal. If you look very carefully at lens focal length comparisons where they move the camera farther and farther away as the lens gets longer, you will see as the lens focal length gets longer, the face looks more idealized, a little bit "flatter".

The only drawback is you need the room to be able to use it.

 

[Derrel]

As far as investing in lenses goes there are only a veritable handful of Nikon DX lenses that are considered investment grade. The vast majority of lenses for the Nikon company makes are designed to cover full frame sensors.

As good as the D7100 is, I think that you will find that an equally modern full frame camera gives even better picture quality and you have access to more and better lenses both new and vintage.

 

[Derrel]

if you are going to use a DX camera there is much to be said for buying DX lenses, especially zoom lenses.

 

[480sparky]

The only drawback is you need the room to be able to use it.

True, but the article said he had a warehouse as a studio. He would still be able to back up with a 300mm to include a car. And with that much floor space and volume, staging the lighting wouldn't be an issue.

 

[ac12]

Thank you!! Is it better to buy an FX lens, since there is always a path to upgrading the camera to a full frame one down the road. Seems like investing in a DX lens means sticking with D7100 for the future.

Interesting delema.
What if you do NOT upgrade to FX.
Then you spent the xtra $ for a FX for maybe no advantage over a DX lens.
Although if you spend for the better FX lenses you will have more IQ than a DX lens.

The problem is there isn't always an easy equivalent FX lens.
A classic example: I want a 70-200 equivalent lens for my DX camera. But until the recent Tamron 35-150, NO ONE made a lens the in DX equivalent focal range of 45-135. The closest was the discontinued Sigma 50-150. So you have to choose between the Nikon FX 24-120 or 70-200. Both are misses, the 24-120 is not long enough and the 70-200 is not short enough.

 

[Dacaur]

I use Canon but same concept. I figure even if I do buy a full frame camera in the future I'm still going to want to keep or upgrade my crop sensor body, as the extra crop means I get more telephoto, so I don't worry if lenses I buy are made for full frame or crop sensor bodies....

 

[Designer]

I have a Nikon D7100. Saw sever videos on how 85mm prime is the best lens for portrait photography.

Just get the 85.

There is more to image quality than merely focal length, and trying to "convert" focal lengths is confusing you.

There is a reason the 85 was recommended, which has very little to do with the focal length, and more the resulting image quality. If you have to back up a few steps, so what?

I also have a D7100 and I will use an 85 if I can't back up enough, and much longer lenses if I have the space. Like 105, 135, 180mm, etc.

 

[adamhiram]

I shoot on a crop sensor, and I think this issue is much simpler than it is often made out to be. Determining the ideal focal length usually comes down to figuring out the desired field of view and how much space you have available for shooting. Whether or not to get FX lenses is often a matter of what is available for the desired focal lengths. Here are the lenses I use most often

• 85mm: This is my go-to lens for headshots and tighter portraits, and is about the longest lens I can use in a typical indoor space. There are a few options available, but the AF-S f/1.4 and f/1.8 are the most common, both of which are FX. I use the f/1.8 version, which many consider to be just as sharp, but at 1/3 the price.
• 50mm: For half or full body portraits, or those with multiple subjects, this is my go-to lens. It is long enough that you don't get much perspective distortion and can still blur the background quite easily, but wide enough that it can be used for more than just portraits. On a crop sensor, it feels a little too long for general use indoors. Most go with the AF-S f/1.4 or f/1.8, both of which are FX. I went with the f/1.8 in this case, simply because it autofocuses much faster. There's a 58mm lens available as well, but at 7x the price, this was never a consideration for me.
• 35mm: These days I don't really use for this lens much, but it's the ideal normal prime if you want to travel light and don't want a larger zoom lens. I got a lot of use out of this in the past, and it's still nice if I want to avoid standing out with a bigger lens. There are DX and FX versions of this lens, and the price difference is big enough that it doesn't make sense to spend more for FX if you don't need it.
• 17-55 (or 18-55, 17-50, etc): This is basically the normal zoom range on DX, which is what spends the most time on my body. It's the least exciting and most useful range. Here, it makes sense to stick with a DX-only lens, since a 24-70 will be missing the very useful wide range. I actually use the wide end for group portraits, typically between 17-24mm, I just need to keep the subjects away from the edges.

Hopefully you find this helpful. If you're looking to take portraits, you can't go wrong with an 85mm, especially with Nikon's big lens sale going on this week. You'll have a narrower field of view than on full-frame, but still very usable in most spaces.