Portraits

[Neuner]

I hope it works for you. When you take some shots, post them. We would love to take a look at them.

 

[pandinus]

I hope it works for you. When you take some shots, post them. We would love to take a look at them.

I'll try to, but today I was not allowed to post photos. I'll try again later on as well.

I allso promise to ask more questions, if and when they should pop up. I've never been loged on to a more helpfull forum. Thanks guys.

 

[Don Simon]

Your camera uses a sub-frame image sensor (the image sensor is less than the full frame of a 35mm film exposure) so you'll need to understand how your D100 receives the light from your Sigma 105mm lens. It will simulate a longer lens; additionally, it will prevent vignetting on cheap lenses because what would have been the corners of a full-frame sensor are actually cropped off by your D100.

Just something to be aware of, especially if you're actually desiring a true 105mm representation.

I feel this needs clearing up... the camera does not have a sub-frame sensor. It just has a smaller sensor than 35mm. To say it has a sub-frame sensor is like saying 35mm film is a sub-format because it's smaller than 6x6. A 105mm will not simulate a longer lens, and it will give a true 105mm representation... it will just appear longer than if you used it on a 35mm camera. I know I'm just being pedantic, but there's a reason, because I think it can cause confusion, for example...

The Sigma lense I've bought is made for digital, so luckily I don't have to think to much about the frame size of the sensor. I have a 35-105mm where I keep forgetting this... Thanks for your advice. =)

... The lens being "made for digital" in this case only means it is optimised for digital sensors (in terms of lens coatings). It will still work with 35mm film too. More to the point, you have to think about the sensor size (or not think about the sensor size) in exactly the same way as with any other lens... because a 105mm lens on your camera is a 105mm lens, regardless of whether it's made for digital. So your 35-105mm lens, when set to 105mm, gives exactly the same angle of view as your new 105mm lens.

 

[GacAttack]

I feel this needs clearing up... the camera does not have a sub-frame sensor. It just has a smaller sensor than 35mm. To say it has a sub-frame sensor is like saying 35mm film is a sub-format because it's smaller than 6x6. A 105mm will not simulate a longer lens, and it will give a true 105mm representation... it will just appear longer than if you used it on a 35mm camera. I know I'm just being pedantic, but there's a reason, because I think it can cause confusion, for example...



... The lens being "made for digital" in this case only means it is optimised for digital sensors (in terms of lens coatings). It will still work with 35mm film too. More to the point, you have to think about the sensor size (or not think about the sensor size) in exactly the same way as with any other lens... because a 105mm lens on your camera is a 105mm lens, regardless of whether it's made for digital. So your 35-105mm lens, when set to 105mm, gives exactly the same angle of view as your new 105mm lens.

OK, this needs further clarification, too. The D100 DOES have a sub-frame sensor in the sense that the image sensor is smaller than its film equivalent. Apples to apples (35mm digital to 35mm film), not apples to oranges (35mm digital to 6x6 film).

A 105mm lens on a sub-frame image sensor has a very specific effect. The angle of view is effectively reduced when compared to its film counterpart, however the image retains all of the other optical properties of a 105mm lens. Let's look at this more concretely:

A 100mm lens on a 35mm film camera will be our baseline. Compared to this, an APS-c sized image sensor (common to many digital SLRs) will have an effective angle of view equal to a 35mm film camera with a 160mm lens. This is due to the "cropping" (not exactly, but the term has utility here) effect caused by a small area of exposure on what would be the film plane.
Here's the neat part. Although your effective angle of view is different, the other optical properties of the 100mm lens remain the same on both the 35mm film and the 35mm digital. The bokah of is not effected, for example, nor will there be any difference how you need to estimate your slowest shutter speed for hand holding.

ZaphodB, I don't mean to turn this into a definition war, but I think that between our two answers, we're getting awful close to being exactly correct.

 

[Don Simon]

No problem, no need for a definition war, but maybe a small skirmish?

Re: the way a 105mm performs on a small-sensor digital camera vs a 35mm sensor/film camera, I agree with what you say. My point in the previous post however was to say that any 105mm when used on a D100 would give the same angle of view (since pandinus seemed to be saying that the lens being "made for digital" would mean not having to worry about the 'crop factor', which is not really correct).

OK, now let battle commence...

OK, this needs further clarification, too. The D100 DOES have a sub-frame sensor in the sense that the image sensor is smaller than its film equivalent. Apples to apples (35mm digital to 35mm film), not apples to oranges (35mm digital to 6x6 film).

But you are not comparing apples to apples either. We are not comparing 35mm digital to 35mm film, because both are irrelevant in the context of the D100. The D100 is not a sub-frame 35mm digital camera, it is an APS-C digital camera, designed with an sensor which is smaller than 35mm film. So were all Nikon dSLRs prior to the D3 (and note the new D300 is still the smaller sensor size). Only Nikon and Canon offer "full-frame" 35mm sensors, and only in their expensive higher-end models (and even then Canon uses smaller sensors for their sports/wildlife models). In the meantime, lenses have been designed to cover the smaller sensor size. Stick a DX lens on the D100; you are using an APS-sized sensor. It's a full-frame APS sensor, it just happens to be smaller than 35mm. The concept of 35mm being "full-frame" is purely because everyone has got used to 35mm being the standard (hence digital cameras listing "35mm equivalent" focal lengths). But for entry to mid level dSLRs, smaller sensors are the standard, not 35mm.

To give another example, Olympus' dSLRs use a sensor roughly 2x smaller than the 35x24mm format. To use the "full frame" concept, that would mean that their dSLRs are "half frame"... except they're not half-frame, they are full-frame; it just happens to be a newer and smaller format - in the same way that 35mm was newer and smaller than larger formats

 

[pandinus]

Oh

It seems that I've been miss informed on what this "Made for digital" actually entails. How ever, I do not see how the size of the image sensor can compared to 35mm film can alter anything other than the angle of view. Making the angle of view for the digital camera somewhere around 157,5mm. The visual effects of using a 105mm lense should in any case remail the same as it would with a film camera not taking in to account the crop that is...?

If I've understood this correctly.

 

[Don Simon]

Correct, the comparison is only really regarding a different angle of view.

The angle of view is not however 157.7mm on digital, and nor is it 105mm on 35mm film. (I assume you multiplied 105 x 1.5 to get that 157.7?). What is measured in millimetres is only the focal length... the angle of view is a different thing entirely, and measured in degrees (°).

The 105mm lens will give an angle of view of around 23° on the 35mm format, or a smaller angle of view of 15° on your D100.

With the 157.7 you are probably thinking of the "35mm equivalent" worked out by applying the 1.5x "crop factor". When you stick a 105mm lens on the D100 and get an angle of view of 15°, it's like using a 157.7mm lens on 35mm film, instead of like using a 105mm lens on 35mm film. Honestly, this doesn't matter in the slightest if you have never used a 105mm lens on 35mm film and therefore have no point of reference.

 

[pandinus]

Thanks for the clarification.
The 157,5 was ment as refrence to the crop factor for my digital camera compared to a 35mm film camera. (So the angle of view would as you say change from 23deg to 15deg. All it would really indicate for me is that I'll have to stand farther from my model, and would propably be in nead of a cell phone to shoot full body shots...(This is why I'm considering a 50mm lense as well, to be able to work with a comfortable distance to my models when working with bouth head/sholder shots and full body.)) Did any of that make sence? I hope it did...

Again thank you for the clarification.

 

[Don Simon]

All it would really indicate for me is that I'll have to stand farther from my model ... (This is why I'm considering a 50mm lense as well, to be able to work with a comfortable distance to my models when working with bouth head/sholder shots and full body.)

:thumbup:

Sounds about right! You need a fair bit of room to work with a 105mm, but it's good for head shots. For full-body shots a 50mm or possibly wider would be good.

Hope my long-winded explanations managed to clear things up rather than confuse them further

 

[pandinus]

:thumbup:

Sounds about right! You need a fair bit of room to work with a 105mm, but it's good for head shots. For full-body shots a 50mm or possibly wider would be good.

Hope my long-winded explanations managed to clear things up rather than confuse them further

Indeed they did... Most things are clear as mud, but this topic seems to be close to crystall clear at the moment, thanks to you guys. I really apprechiate it.

 

[jstuedle]

The lens being "made for digital" in this case only means it is optimised for digital sensors (in terms of lens coatings). It will still work with 35mm film too. More to the point, you have to think about the sensor size (or not think about the sensor size) in exactly the same way as with any other lens... because a 105mm lens on your camera is a 105mm lens, regardless of whether it's made for digital. So your 35-105mm lens, when set to 105mm, gives exactly the same angle of view as your new 105mm lens.

Also, many made-for-digital lenses only have an image circle that will cover the clipped or APS size chip. That is to say the lens will not project an image that will cover a full 35mm frame. All DX format lenses will show severe fall-off on a full frame sensor.

 

[Don Simon]

Good point. The lens in question was only "optimised" for digital sensors (which often gets confused with being "made for digital") so it would work fine on either 35mm frame or smaller. But as you say, other lenses designed specifically for and only for APS-C sensors (Canon EF-S, Nikon DX, Pentax DA etc) won't perform too well on full-frame sensors and I believe in Canon's case may not even fit...

But hopefully folks will not be buying APS-C lenses along with a new 1Ds MkIII or D3 unless they have way more money than sense

 

[selmerdave]

The 105mm lens will give an angle of view of around 23° on the 35mm format, or a smaller angle of view of 15° on your D100.

I need help with this actually. It seems to me that a lens is going to give a certain angle of view regardless of the size of the sensor. With a smaller sensor and the same angle of view, a smaller portion of the scene is captured, which in my head makes sense as to what would be going on with a digital sensor. Does the angle of view change from the centre of the lens to the outside, giving a different angle of view at different points? Are the depth of field and foreshortening characteristics the same or different with the same lens on film and digital? Thanks.

Dave

 

[pandinus]

I need help with this actually. It seems to me that a lens is going to give a certain angle of view regardless of the size of the sensor. With a smaller sensor and the same angle of view, a smaller portion of the scene is captured, which in my head makes sense as to what would be going on with a digital sensor. Does the angle of view change from the centre of the lens to the outside, giving a different angle of view at different points? Are the depth of field and foreshortening characteristics the same or different with the same lens on film and digital? Thanks.

Dave

The lenses angle of view is a relative constant, but since a 35mm film is larger than the APS sized image sensor more of the light will be captured on the 35mm film. If an image sensor and one frame of 35mm film was placed next to each other one would see the size difference. The simple fact is this. The light passing thrugh the lense will allways be the same, and the image the lense captures will be a constant. But due to the simple size difference between the 2 media, the 35mm film wil capture more of the image than the image sensor. This will give the image a different angle of view. (a smaller angle of view.) I hope this helped, It would be easier to demonstrate this physically than to as I've done here: write it down in this manner...

 

[selmerdave]

Actually, thanks, that did it. If I visualize the light going from one side of the sensor through the centre of the lens, I can see how the size of sensor would affect the angle of view, giving a smaller one a narrower angle. Not too hard to figure out, but I just didn't have my head around it until your choice of words. Thanks.

Dave