9 replies to this topic

[brad10281]

I'll be taking a stab at senior portraits for my daughter this year. I have most of the required equipment but I'll be renting the lenses. I'm really intrigued by the Sigma 50-100 Art lens. I currently have a Sigma 18-50 2.8 but it's not giving me the results I want. I've shot with the Nikon 50mm 1.8 in the past, which worked out great, but I don't have that lens anymore. I'm considering renting the 50mm & 85mm, but would the Sigma work just as well while covering a broader range? I'm using a dx body.

Looking for thoughts on using the Sigma instead of the primes.

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[Ron]

The Sigma 50-100 Art lens may be your best choice assuming you're cool with the price. On DX it works out to a 75-150mm lens which covers the traditional portrait range. It is also fast (f/1.8) so you'll easily be able to throw the background out of focus. I don't personally own this lens so I can only judge it's image quality by what I've seen others do and from the reviews I've run across. And, they have been mostly excellent. 

 

I personally use either my AFS Nikkor 70-300mmVR or AFS 85mm f/1.8 for portraits but then, I'm cheap.

 

As far is using primes rather than zooms, for me at least (because I'm getting old), comes down to size and weight. The 85mm that I use weighs a whole lot less than the 70-300. The down side is that you have to do all your zooming with your feet. If you're in a tight spot that may not be practical. The Sigma 50-100 looks even larger than my 70-300 so it won't go unnoticed. That's another possible drawback.

 

Assuming you're OK with the price, size, and weight, I think I'd go with the Sigma.

 

--Ron

[Merco_61]

The 50-100 will probably work well for the head-and-shoulders shots. For full-body and environmental portraits on DX, I wouldn't like to be without a fast 35 or even a fast 24.

 

Why doesn't the 18-50 give you the results you want?

[brad10281]

Thanks for your input Ron. Keep in mind I'll be renting the lenses. I figured using a single zoom would keep it simple as I wouldn't need to switch out lenses. Oddly enough, every thing I see online shows photographers mostly using a 70-200mm on an FX camera...so I figured the 50-100mm would get me close to that but yet have a wider aperture. I think I'm leaning toward the Sigma at this point.

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Why doesn't the 18-50 give you the results you want?

Just comparing to some shots I took with the 50mm 1.8 (years ago), I think the 50mm just looks a lot better. I haven't done any real tests with 18-50mm yet so I don't have a real comparison quite yet. I'm thinking the 18-50mm and the 50-100mm should work well for what I need. Would love to try the 85mm though.

I'm curious to know if anyone thinks I need something longer than 100mm.

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[fallout666]

also 50mm will be about 75mm since all or most 50mm are full frame lenses. that probably why does not like the 18-50. since not giving him the 75mm reach he use to. 

[brad10281]

also 50mm will be about 75mm since all or most 50mm are full frame lenses. that probably why does not like the 18-50. since not giving him the 75mm reach he use to.

Ok, now I'm confused. I've researched this online and came to the conclusion that there is ALWAYS a crop factor when using an APS-C sized sensor, whether the lens is made for DX or full frame. Can anyone clarify this? I don't have an FF lens to test with.

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[Merco_61]

Focal length is a physical property of a lens. It does not change with the sensor size. There are some compacts that are only marked with the FX equivalent focal lengths, but for ILCs, the focal lengths are not recalculated as it would be very frustrating when mixing DX and FX lenses on the same camera.

The difference between a DX and an FX lens is the image circle. The DX lens projects a smaller image circle to keep the mass and size down. This is possible because of the smaller sensor size.

[brad10281]

I thought I'd post an update on this topic. I ended up purchasing a Nikkor 50mm 1.8 which is an FX lens and it gives roughly the same view as my Sigma (slight difference). So, to answer my own question, it doesn't seem to matter if it's a DX or FX lens, the focal length remains the same.

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[F2-Man]

I thought I'd post an update on this topic. I ended up purchasing a Nikkor 50mm 1.8 which is an FX lens and it gives roughly the same view as my Sigma (slight difference). So, to answer my own question, it doesn't seem to matter if it's a DX or FX lens, the focal length remains the same.

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Correct, on a DX camera, you can use both, lenses made for the smaller sensor, or a lens made for a full frame sensor.

 

A 50mm FF lens on a FF camera has normal lens Field of View. (FoV).

A 50mm FF lens on a APS-C camera has a Field of View of a short portrait lens. The sensor "CROPS"  the larger image circle of the FF 50mm lens.

A 50mm lens made for an APS-C sensor will have a smaller image circle than the 50mm FF lens has and therefore have a slight telephoto effect. (75mm)

You would need a 35mm APS-C lens on an APS-C camera to have the same FoV of a 50mm FF lens on a FF camera.

 

The smaller the sensor, the shorter the focal length needs to be to achieve the same FoV of larger sensor cameras. 

[Marcus Rowland]

My feeling on this is that a good 50mm is a very suitable lens for portraiture on a DX DSLR; it's got about the same angular coverage as say a 75mm lens on 35mm, as noted above, and because they were made in huge numbers you often find good deals on them (especially the earlier AF lenses driven by a motor in the camera body, if your camera can use them); there's also the advantage of wide aperture, which is great for focusing under studio conditions, and gives you an easy way to soft focus the background if necessary.