1.6 crop "issue"

[bob_bell]

I know everyone is going to say this is beat to death, but I question

if most people are really wrong on this topic. Let's say we are

talking about the D60, 300D, 10D bodies and let's say we are talking

about a 200mm lens. When we apply the 1.6 crop to the image, we are

really reducing the number of degrees that the lens sees and not

increasing the lenth of the zoom. So for example at Canon 200mm lens

sees about 12 degrees of area on a 1Ds or Film body but will only see

8 degrees on a 1.6 crop lens, right? so this means the lens is still

equiv to 200mm, but we are just seeing less of the picture, right?

so why do people with a 10D, etc... so why do people say a 200mm lens

is equiv to 320mm? when it is really like putting barn doors on the

end of the lens

[jim_larson1]

Right. Beat to death.

 

Yes, you are seeing less of the picture. To get a "normal" sized "print", you have to enlarge the image. Once enlarged, the framing (not depth of field) would be similar to what you see with a longer lens on a larger sensor.

[jbq]

Totally dead horse.

 

What Jim said. Your reasoning looks all fine until you realize that suddenly the cropping means that you only get 5x7 prints instead of 8x10. Printing a 5x7 from a 10D and cutting the center 5x7 from an 8x10 print from film are *exactly* the same.

 

When you decide to enlarge more because you want 8x10 prints from your 10D with its 200mm lens, you get exactly the same 8x10 prints as you'd get with a 320mm lens on 35mm film printed full frame.

[jim_mueller2]

<<we are really reducing the number of degrees that the lens sees and not increasing the lenth of the zoom>>

 

Yes...that's true. BUT...there are more pixels packed into that "reduced number of degrees" which aids the digital enlargement.

 

If you have 6.3 MP spread across an area of 24X36mm versus 6.3 MP spread across a cropped image of 12X18mm, both images can be blown up to 8.5" X 11" with equal resolution because both have exactly the same number of pixels. But the 12X18mm crop has been blown up 1.6X larger with equal resolution (due to equal pixels).

 

I'm not saying that the 1.6 crop fact is AS good as a 1.6X longer lens BUT it does help the digital enlargement. The image does benifit somewhat from that digital enlargement.

[markci]

It's equivalent only in the sense that it has the same field of view.

 

But "most people," certainly most people here, have been aware of that for a long time. That's why it's called a "crop factor."

[bob_bell]

Mark, There are a lot of people here that think their 200mm with a 1.4TC on a 10D is 448mm when in reality it is 280mm.

 

Jim, thx for that bit of info.

[phil]

And 35mm is like putting barn doors on medium format, for much the same reason. Just choose the lens that produces the framing that you want with the camera that you have. Focal length produces expectations of framing in the format you want to shoot. We obsess over the crop factor because we're predominantly 35mm shooters adapting to the digital world, so if we say 200 on 10D == 320 on EOS-3 we're just normalising our expectations. Obviously the focal length of a piece of glass doesn't change, nor does the DOF.

[mark u]

Jim, your argument is very hypothetical at best. A 1Ds has over 11 million pixels for its 24x36mm sensor - and the Kodak full frame models have 14 million. When you compare the pixel spacings with the circle of confusion diameter it immediately should be clear that they are both capable of higher resolution and ultimate print size than a 6.3 MP 1.6x crop body. Pixel quality is also very important in enlargement, as poor (small) pixels have to be subjected to more digital manipulation that results in loss of detail. Think of the poor results from an 8MP small sensor Sony 828 by comparison with a 6.3MP 10D.

[mark u]

So far as depth of field is concerned, I refer you to Bob Atkin's excellent article on this site at

 

http://www.photo.net/learn/optics/dofdigital/index.html

 

It clears up a lot of common misconceptions about this issue.

[citizensmith1664875108]

I think Jim's point may have been that the RebelD (for instance) actually has a higher pixel density than a 1Ds. So if we take two photos using a given lens, and then crop the 1Ds image down to make it look the same as the RebelD's 'cropped' image, its actually the RebelD that has more raw data.

 

Of course number of pixels is just one piece of a bigger puzzle, but the point is definitely there.

[citizensmith1664875108]

Nothing like the correct mix of Sadism, Necrophilia and Beastiality. Or as others put it, flogging a dead horse. :)

[will_perlis]

"I question if most people are really wrong on this topic."

 

As explained above, yes. But most people would rather listen to happy talk than realistic talk. Strangely enough, the new Canon Lens Work III book lays it all out, something I never expected to see from any maker.

[markci]

<i>Mark, There are a lot of people here that think their 200mm with a 1.4TC on a 10D is 448mm when in reality it is 280mm.</i>

<p>

Well "a lot" is certainly subjective, and some people are too clueless to ever figure it out. However, your point is certainly one that has been made over and over here. And over the past couple of years the number of people who have posted things that indicate they think the focal length has actually changed has fallen off dramatically, while the use of the term "crop factor," virtually unheard of a couple of years ago, has almost completely replaced "multiplier." In 2001 you would have had people vehemently disagreeing with your post and insisting the focal length changes.

[johnlund]

You say "crop factor", I say "format". Let's not get worked up over semantics when someone uses terms like "effective", "equivalent", or even "multiplier" to describe the same phenomenon unless it's clearly used in a wrong-headed way. If you're going to be a stickler, at least call it a <I>1 / 1.6</I> crop factor <I>in relation to 35mm</I>.

<br/>

<br/>

 

A 1996 photo.net article on <I>equivalent</I> focal lengths:

<a href=http://www.photo.net/equipment/medium-format/focal-length-conversion> http://www.photo.net/equipment/medium-format/focal-length-conversion

</a>

[mormegil]

Would the "crop" or "multiplier" or "magnification" or "format" effect be analogous to using a 1.6x TC?

 

With a 200mm lens, you don't gain the sharpness of a 320mm lens. You have the same sharpness blown up bigger. So that's an optical magnification, which is a lot better than a digital (interpolated) magnification.

 

Since a TC can't increase the sharpness of the lens it's mounted to (loosing sharpness if anything), but does change the Field of View, could this be considered as a similar effect?

[kelly_flanigan1]

Imagine using 35mm film in a Rolleicord; with an adapter. Yes the "1.6" issue is at least 1/2 century old.

[mark_mankey]

I think most everyone knows it is a crop.

 

From a practicality standpoint when talking about focal length it seems easier to describe the focal length the image will look as if it was taken at, and what you see through your viewfinder, rather than going on about the specific math that we all know fairly well.

 

We can always sit around and complain about lost pixels and such, but that is pointless when there is nothing to do about it. The real question is do we like our photographs, and do we even notice the difference. If you feel the trade off is worthwhile, yay, if not wait for a full sized 35mm sensor.

[michael focus97.com lee]

"And 35mm is like putting barn doors on medium format, for much the same reason. Just choose the lens that produces the framing that you want with the camera that you have. Focal length produces expectations of framing in the format you want to shoot."

--Well said, Jeffrey.

 

To the original question, shooting with a 200mm on a 10D seems a heck of a lot like shooting with a 320mm because the field of view is the same. It's framed like a larger focal length lens, prints look like they are from a larger focal length lens, and you have to worry about handheld shutter speed like with the larger focal length lens.

 

So funny to see people get so seemingly po'd about a subject someone is genuinely interested in understanding. This is a forum, right? If the nature of the thread is old, irritating, or whatever, then why not just move on? People complain about the same tired old questions, so they give the same tired old complaints.

[raymond bradlau]

Regarding hand helf shutter speed, I find with the 1.5 factor of my camera I do need

to increase just like I was using a longer lens on a 35mm

 

FYI I think Jim Mueller posted the best answer to this type of thread I have seen so far

(I have read many)

 

I dont uderstand the comparison of 35mm film in a MF body, a better way (I think)

would be 800 speed 120 film vs Pan F 50 in 35mm, yes the 35mm is smaller but it

has more fine detail packed into that smaller frame

 

PS I shoot Nikon I was over here reading some posts on the Mk II...... WOW! what a

machine