Digital effect on lens

[knobstone]

I understand that with the D100, and other digital SLRs, the lens is

multiplied by 1.5. Does this mean that if I am using, say, the

105mm, that thru the viewfinder I see as if I have a 155mm, or does

it just crop the recorded image?? Having no experience whatsoever

with digital SLRs, I'm a bit confused about this. Thanks in advance

for your help. Joe

[loel_skoch]

A 24 lens becomes a 36, a 200 becomes a 300, and a 300 a 450,

 

its because the CCD is smaller than 35mm.

 

It's really nice when you want to get closer but a pain when you want a wide angle shot.

[aaron_ng]

Hi Joe,

 

The effect is like a crop. I'm assuming that you have used film SLRs and know about the field of view of different focal length. So say you have the 105mm, and you stand on the same spot. The field of view would be the same on both the digital and film SLR, but the digital will show the middle section equivalent of a 1.5 multiplication focal length. However, if you choose to step back so that you can frame the subject properly with that 1.5x multiplication, the field of view changes so it is not the same anymore.

 

Regards,

Aaron

[mbetea]

It's a misconception that the lens' focal length is "multiplied 1.5x". What it actually means is the Angle of View is cropped by 1.5x, there is no cropping after the image is recorded. The size of the sensor determines how much of the scene is actually recorded.

 

What it means is, say you have a 35mm lens attached to your d100. Now a 35mm lens, if it was used on a 35mm film body has a AOV of 63 degrees. Take 63 degrees and divide it by the 1.5 crop factor, you get 42 degrees. Which would give you roughly the same AOV as a 50mm lens would on a 35mm film body (actually 52mm).

 

You will see in the viewfinder only what the sensor will record (or I should say 95% of it). So it's not magnifying the image/subject, a 300mm lens on a d100 will not get you any closer than a 300mm lens on a 35mm film body will. But on the d100 with a 300mm lens you get a AOV that mimics a 600mm lens on a 35mm film body.

 

Don't worry, it seems confusing at first but after a bit it'll be no problem. Just think, whatever the focal length of your lens is, multiply it by 1.5. So an 18mm lens on a d100 will have approximately the same AOV as a 28mm lens on a 35mm film body.

[matthew]

When you look through the viewfinder of a DSLR, you will see it as if you have a 155mm.

[gilbert_c1]

Talking about perspective, the relationship between near scene and distance scene in a photo, it is still a 105mm lens not a 155mm lens. But talking about angle of view, the coverage, it's like a 155mm. So I'll say it's a 105mm with smaller coverarage.

[cham_saranasuriya]

Hi Guys,

 

I have the same problem in understanding it. I have never touched a digital camera. Can I clarify my understanding:-

 

1) The perspective is essentially a function of the focal length so for a 105mm lens it is the same whether it is in a digital or a film body

 

2) The difference being the digital image is cropped to narrow the angle of view so there would be 1.5 magnification or crop depending on the camera body

 

3) However the perspective is different to an equivalent image by a film camera lens (eg in this case 155mm lens on a 35mm film body) as 155mm lens has an inherently different perspective as opposed to a 105mm lens

 

4) When a 105mm lens is attached to a Medium format camera (hypothetically, provided the image circle is wide enough) because of the larger image area there would be the opposit effect on the angle of view (eg equivalent to a 70mm view on a 35mm camera). This effect is pronounced even further in Large format

 

Please correct me if I am wrong. This is my working understanding. Hope this will not confuse anyone.

 

Cheers,

[ci_p]

perspective is a function of where you're standing

[ellis_vener_photography]

1) The perspective is essentially a function of the focal length so for a 105mm lens it

is the same whether it is in a digital or a film body.<P><B>Perspective rendition is a

function

of where you're standing in relation to the subject and background.</B><P>

 

 

 

2) The difference being the digital image is cropped to narrow the angle of view so

there would be 1.5 magnification or crop depending on the camera

body.<P><B>Apparent magnification of focal length but really it is a reduced angle

of view than what you would get with that lens on a 35mm SLR film camera (If he

short hand forr a digital SLR is a DSLR, should we start referring to a film SLR

cameras as an FSLR?).</b><P>

 

 

3) However the perspective is different to an equivalent image by a film camera lens

(eg in this case 155mm lens on a 35mm film body) as 155mm lens has an inherently

different perspective as opposed to a 105mm lens. <P><B> The perspective

rendition is the same if you stay in the same place. What is different betwen a a

neffective 155 (really the 105) and a true 155mm on an FSLR is the depth of field for

a given f-stop. The effective 155 still performs like a 105mm in that regard, whilea

true 155 onan FSLR will have shallower depth of field when set to the same aperture.

</B><P>

4) When a 105mm lens is attached to a Medium format camera (hypothetically,

provided the image circle is wide enough) because of the larger image area there

would be the opposit effect on the angle of view (eg equivalent to a 70mm view on a

35mm camera). This effect is pronounced even further in Large format.<P> <B>By

Jove , I think he's got it!</B>

[ShunCheung]

This question comes up once in a while. If you have ever used larger formats such as 6x6, different film/sensor sizes is a concept very easy to understand. Unfortunately, we (including me) have been using the actually incorrect "1.5x factor" as a convenient expression, leading to more confusion.

[cham_saranasuriya]

Hi Ellis,

 

Thanks for correcting.

 

Cheers,

Cham