Dumb question.. lens for D800

Started May 16, 2012 | Discussions
swap nil Forum Member • Posts: 62
Dumb question.. lens for D800

People don't bash me but I have a very dumb question....

If I have 28 mm 1.8, why would I need the 50 mm 1.8 or even the 85 mm 1.8. Wouldn't the fact that I have a huge resolution allow me to crop to the extent that I get same details as with a 85 mm?

Like I said, people please don't bash me. I asked because a lot of people have the same impression from 200 mm to 300 mm for normal photos (not large prints) so why not at the narrow side of the focal lengths..

Eagerly,
Swapnil

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brokensocialscenester Regular Member • Posts: 410
Re: Dumb question.. lens for D800

No bashing. One of the bonuses of longer lenses is that they give you even more pixels to put on the subject. Additionally, you get different perspectives with different lenses that you can't replicate simply through cropping. This shot below of my D3100 and 35/1.8 was taken with a 35/2 on a D700. It would look quite different if I'd been twice as far away and used a 70mm focal length, even though the magnification and number of pixels on the image would have been the same.

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russbarnes Senior Member • Posts: 1,660
Re: Dumb question.. lens for D800

The difference between 28mm and 85mm is huge at the wide end. The difference between 200 and 300mm is not at a telephoto distance (in my view). You need to borrow a big 10x zoom like the 28-300 and see for yourself...

Take a look here too:

http://www.tamron-usa.com/lenses/learning_center/tools/focal-length-comparison.php

swap nil wrote:

People don't bash me but I have a very dumb question....

If I have 28 mm 1.8, why would I need the 50 mm 1.8 or even the 85 mm 1.8. Wouldn't the fact that I have a huge resolution allow me to crop to the extent that I get same details as with a 85 mm?

Like I said, people please don't bash me. I asked because a lot of people have the same impression from 200 mm to 300 mm for normal photos (not large prints) so why not at the narrow side of the focal lengths..

Eagerly,
Swapnil

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Fearless_Photog Senior Member • Posts: 1,250
Re: Dumb question.. lens for D800

A longer lens with the same aperture will allow for more subject isolation, it will also generally have less distortion, although that can be corrected in post, and a center crop will have less distortion than the full frame. Not to mention the fact that each lens will have it's own specific optical characteristics and rendering.

However, cropping an image will result in not only less resolution, but less total DR, less high ISO performance for a given print size, less possible subject isolation even relative to using the same lens and filling the frame since you'd be farther from the subject... someone else can probably think of even more reasons not to do it.

As with any other aspect of image quality, such as exposure, white balance and focus, why wouldn't you want to get your framing as close to what you want in the final image as possible in camera? I'd always want to have highest quality to work with when editing, and that would mean trying to fill the frame with the composition I want in camera.

I really try to avoid cropping altogether, the exceptions being when I'm focal length limited and want a tighter shot on say, a bird in flight, than my lens would allow me to capture. When there's something distracting in the frame I want to get rid of, or when I'm printing at an aspect ratio other than 3:2.
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russbarnes Senior Member • Posts: 1,660
Re: Dumb question.. lens for D800

Fearless_Photog wrote:

I really try to avoid cropping altogether

Good call, I'm exactly the same. It's in the frame for a reason... that's why I have every focal length covered from 21-200mm with 7 lenses.

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tdptdp Regular Member • Posts: 496
Re: Dumb question.. lens for D800

Try an experiment: shoot a wide angle lens and a telephoto with the same framing. Since I shoot a lot of landscape, that's what I would pick as a subject. You can do this with a model's face, but he won't like the 35mm so much. Observe the apparent distance between objects.

The telephoto lens will compress the apparent distance between objects. The wide angle will pull near objects nearer and push distant objects further away.

Playing with perspective in this way can lead to some very striking photographs.

tarnish Senior Member • Posts: 1,470
You can crop from 85mm too

Your deep crop to simulate 85mm from a 28mm original could be applied to an 85mm original source image...

OK, so if you wanted a 250mm final field of view wouldn't you rather be cropping from 85mm instead of 28?

But yes there is a cropping flexibility in the D800 that can free you up. Imagine using a auperb prime ultra wide angle like the Zeiss 21mm instead of a bulkier zoom. If you weren't going to be making a gigantic print then cropping to simulate 35mm is a real possibility. But you can take things too far, there are always limits.

Mazevision Forum Member • Posts: 58
Re: Dumb question.. lens for D800

I think you can crop to get 1.5x the lens focal length without too much compromise in IQ and resolution, to get Dx equivalent IQ. People don't talk about wide angle FOV cropping (let's say between 24-100mm) simply because these focal length are available, and not too expensive, with both primes and zooms. People who buy the D800 want the best IQ anyway.

But try to get a cheap 300mm or 400mm with f2.8 and VR

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Manny82 Contributing Member • Posts: 611
Re: Dumb question.. lens for D800

Why would a D800 owner ask such a question? Why on earth did you buy a D800?

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OP swap nil Forum Member • Posts: 62
Re: Dumb question.. lens for D800

To everyone.. Thanks. Your comments do make a lot of sense when I read through and clarifies my thought. I should have tested the same with the lenses I had....

Thank you once again.
Swapnil

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jaysonmc Senior Member • Posts: 1,148
Perspective is the the answer.

The best example is take a picture where you have the moon in the frame and a person from head to toe with the 28mm.

Now if you take the same picture with an 85mm (person is visible from head to toe), the moon will be much bigger.

If you take the 28mm and crop it so the Moon is the same size, what happens is the person becomes enormous (you no longer able to see the from head to toe).

Focal length is about subject relationships to each other.

There are other differences too (depth of field), but this is the main point.

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mattr Veteran Member • Posts: 3,523
Re: Perspective is the the answer.

jaysonmc wrote:

Focal length is about subject relationships to each other.

This statement is a bit confusing.

Perspective only depends on your position relative to the subjects. Focal length has nothing to do with it.

You can take two D800 pictures with the same perspective with the 85mm lens and the 28mm lens. When the 28mm result is cropped to the same framing as the 85mm result, subject relationships are the same because the perspective remained the same. Of course, the 28mm crop will have only 4MP left.

tdptdp Regular Member • Posts: 496
Re: Perspective is the the answer.

mattr wrote:

You can take two D800 pictures with the same perspective

Reading comprehension ain't what it used to be

BelePhotography Regular Member • Posts: 373
Re: Perspective is the the answer.

Perspective has everything to do with it. If you want the same information in the picture with different focal lengths the perspective will change:
http://www.photozone.de/focal-length-and-perspective

Regards,
Bele

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mattr Veteran Member • Posts: 3,523
Re: Perspective is the the answer.

BelePhotography wrote:

Perspective has everything to do with it. If you want the same information in the picture with different focal lengths the perspective will change:

Focal length does not affect perspective, only your position relative to the subject does. If you want to change focal length with a constant sensor size while keeping the subject framing the same , you have to move. The perspective changes because you move, not because the focal length is different. If you crop (effectively changing sensor size) you can change framing without changing perspective.

jaysonmc Senior Member • Posts: 1,148
Photography 101

If you don't think focal length affects perspective, then you might need to take a photography course. This is basic photography. Perhaps a dictionary would convince you?

If STAND in the same place and take a picture with a 20mm lens and a 200mm lens where the subject is a person that is 10 feet away and a tree behind that is 600 feet away; if you change lenses then your perspective changes. The pictures are NOT the same.

Perspective Definition:
a technique of depicting volumes and spatial relationships on a flat surface.

If you want to refute what it means, that's fine. But it does not make it true.
Perspective in Photography is just not "Forced Perspective"

mattr wrote:

BelePhotography wrote:

Perspective has everything to do with it. If you want the same information in the picture with different focal lengths the perspective will change:

Focal length does not affect perspective, only your position relative to the subject does. If you want to change focal length with a constant sensor size while keeping the subject framing the same , you have to move. The perspective changes because you move, not because the focal length is different. If you crop (effectively changing sensor size) you can change framing without changing perspective.

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mattr Veteran Member • Posts: 3,523
Re: Photography 101

jaysonmc wrote:

If you don't think focal length affects perspective, then you might need to take a photography course. This is basic photography. Perhaps a dictionary would convince you?

yes, that's what I don't think

If STAND in the same place and take a picture with a 20mm lens and a 200mm lens where the subject is a person that is 10 feet away and a tree behind that is 600 feet away; if you change lenses then your perspective changes. The pictures are NOT the same.

no, if you change lenses your framing changes, perspective remains the same

indeed "pictures" are not the same (because framing changes)

jaysonmc Senior Member • Posts: 1,148
Re: Photography 101

There are really two types of perspective going on and you are only seeing the one.

1) The distance of subjects to the film plane and their relationships to another (this does not changed with focal length). People change this via Forced/Linear Perspective. Or Viewpoint of the camera.

2) The way the viewer sees the scene in relation to the space it fills on the frame (this does change with focal length). You can call this FoV if you want, but FoV is a function of the viewer's perspective.

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BelePhotography Regular Member • Posts: 373
Re: Photography 101

indeed "pictures" are not the same (because framing changes)

Exactly - the pictures are not the same, because you now moved and now have different perspective. the focal length doesn't change the perspective, but it demands you to change it to get the same picture.

cropping a wide angle picture will not change the perspective of the picture, but it will not give you the same picture as with a true tele lens - because of perspective. so the answer to why you need different focal lengths is perspective.

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ortega New Member • Posts: 12
Re: Photography 101

I tried it some years ago and this is the result

photo taken with D70 and the kit lens, 18-70mm, camera mounted on a tripod with the subject at the same place, so camera and subject did not move, only the focal length was changed.

so only if you move the camera to subject distance will the perspective change.
also note the change in DOF

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