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MikeWhis

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sevencrossing said:
Your are NOT changing the focal length
It is just a guide of an equivalent lens

If you are as old as dirt and used to thinking focal length in terms of a full frame Nikon F 35mm film camera and have just bought a D7000 you want to know the equivalent field of view

if you put a 50mm lense that you used on your Nikon F, on your new D7000, it will have the Equivalent field of view as an 80mm lens on the F

but it is still a 50mm lens and laws of physics have not changed

And I know that. But why do we want to know the lenses' focal lengths? I want to know what my image is going to be like, not what the gear is. The focal length doesn't change. The fstop doesn't change. But the depth of field and field of view changes, and that's all we want to know. As long as I want to know the depth of field and field of view, I'll have to multiply the crop factor to the focal length and fstop to get a meaningful and fair comparison. Equivalent focal length and equivalent fstop shows a great way to know what kind of depth of field you're getting and what kind of field of view you're getting. Unless, all your life you've been shooting only with one format. It doesn't matter when you are not changing format, but it matters once you start comparing different cameras+lens combinations with different formats.

And that's the reason I said the word 'equivalent'. I have not once said the lens changed.

Posted 10 months ago #
MikeWhis

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tcole1983 said:
Unless I am totally mistaken in my photography knowledge the aperture is how much the diaphragms of the lens are opened or closed. So as I mentioned before if you have a lens at F2.8 the aperture is opened the same amount for both FX and DX bodies...there is no difference. The difference is in the sensor and the amount of area focused on the sensor by the lens. The crop factor only applies to the "focal length" in terms of the sensor is cropping the image to create an image that appears longer in focal length...like this http://www.garydatesphotos.com/superphotodude/wp-content/uploads/2010/11/crop-circle.jpg

There is nothing about the aperture in the crop factor. Take the new FX bodies for example...they have a crop mode. You are shooting the same lens. What happens when you put the camera in crop mode? Nothing except you are cropping the image to a smaller size...same f-stop, same focal length, but you take a smaller rectangle of the total round area that the lens capturing the image of. The camera aperture does not change when you change from the FX mode to crop mode.

Hmm, you're kinda wrong. No offence. Let's say we're shooting with two lenses to get the same field of view.

24mm on DX.
36mm on FX

Fair enough. Their field of view.

Okay, let's factor in their f/stop.

24mm f/2.0 DX
36mm f/2.0 FX

Therefore, the entrance pupil (aperture) size of the DX lens is 24mm f/2.0 = 12mm.
Therefore, a 24mm f/2.0 DX lens has an aperture size of 12mm.
And the 36mm f/2.0 FX lens will have an aperture size of 18mm.

How is their aperture size the same? You might be saying that you have to use the same focal length for a fair comparison. But that mentality is wrong. Having the same field of view is important for a fair comparison.

Posted 10 months ago #
MikeWhis

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tcole1983 said:
Unless I am totally mistaken in my photography knowledge the aperture is how much the diaphragms of the lens are opened or closed. So as I mentioned before if you have a lens at F2.8 the aperture is opened the same amount for both FX and DX bodies...there is no difference. The difference is in the sensor and the amount of area focused on the sensor by the lens. The crop factor only applies to the "focal length" in terms of the sensor is cropping the image to create an image that appears longer in focal length...like this http://www.garydatesphotos.com/superphotodude/wp-content/uploads/2010/11/crop-circle.jpg

There is nothing about the aperture in the crop factor. Take the new FX bodies for example...they have a crop mode. You are shooting the same lens. What happens when you put the camera in crop mode? Nothing except you are cropping the image to a smaller size...same f-stop, same focal length, but you take a smaller rectangle of the total round area that the lens capturing the image of. The camera aperture does not change when you change from the FX mode to crop mode.

To get the same field of view when using the crop mode in the FX lens, you'll have to use a shorter focal length. Hence, the greater depth of field.

Posted 10 months ago #
TaoTeJared

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Math is still wrong or rather you are applying the incorrect mathematical equations. It appears you are applying trigonometry where it should not be applied.
The flange distance is the same, image circle is the same, focal length is the same, opening in the lens is the same. None of that changes.

FX->DX is the same as shooting a 8x10 negative and then crop it down, to a 4x5 in the dark room. The angle of view is narrower.

I think the issue is you are incorrectly applying how to calculate Depth of field changes. Just because the depth of field changes (about 1/3 more for FX) you NEVER describe a lens as loosing an f-stop. Saying it looses an f-stop is saying it is loosing the ability to capture light which is absolutely not true. The gain of DOF is actually more due to perceived perspective of the smaller format, not to any physical change.

Posted 10 months ago #
PB PM

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Can you people just agree to disagree and get back to the subject of this thread... you know, the D400, not depth of field, apparent apertures (rubbish) or math.

Posted 10 months ago #
tcole1983

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Here we go...again not sure about merit here, but something...

http://snapsort.com/cameras/Nikon-D400

Posted 10 months ago #
PB PM

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Looks like someone just made a post with a few tidbits from rumors that have been around for about a year now, nothing new to see there.

Posted 10 months ago #
MikeWhis

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TaoTeJared said:
Math is still wrong or rather you are applying the incorrect mathematical equations. It appears you are applying trigonometry where it should not be applied.
The flange distance is the same, image circle is the same, focal length is the same, opening in the lens is the same. None of that changes.

FX->DX is the same as shooting a 8x10 negative and then crop it down, to a 4x5 in the dark room. The angle of view is narrower.

I think the issue is you are incorrectly applying how to calculate Depth of field changes. Just because the depth of field changes (about 1/3 more for FX) you NEVER describe a lens as loosing an f-stop. Saying it looses an f-stop is saying it is loosing the ability to capture light which is absolutely not true. The gain of DOF is actually more due to perceived perspective of the smaller format, not to any physical change.

Ah... You don't lose a fstop, you lose an EQUIVALENT fstop.

Posted 10 months ago #
MikeWhis

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TaoTeJared said:
Math is still wrong or rather you are applying the incorrect mathematical equations. It appears you are applying trigonometry where it should not be applied.
The flange distance is the same, image circle is the same, focal length is the same, opening in the lens is the same. None of that changes.

FX->DX is the same as shooting a 8x10 negative and then crop it down, to a 4x5 in the dark room. The angle of view is narrower.

I think the issue is you are incorrectly applying how to calculate Depth of field changes. Just because the depth of field changes (about 1/3 more for FX) you NEVER describe a lens as loosing an f-stop. Saying it looses an f-stop is saying it is loosing the ability to capture light which is absolutely not true. The gain of DOF is actually more due to perceived perspective of the smaller format, not to any physical change.

And dude, perspective relies on equivalent focal length, not the actually focal length. Or else all those point and shoot cameras would have mad perspective distortion.

Posted 10 months ago #
sevencrossing

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Mods, please can we have an equivalent thread? This has nothing to with the D400 ,or any else of interest , for that matter

Posted 10 months ago #
TaoTeJared

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sevencrossing said:
Mods, please can we have an equivalent thread? This has nothing to with the D400 ,or any else of interest , for that matter

+1

I say just delete it all out or move it to a different thread.

Posted 10 months ago #
BarryH

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sevencrossing said:
Mods, please can we have an equivalent thread? This has nothing to with the D400 ,or any else of interest , for that matter

+1

I was really interested in reading everyone's thoughts about the D400 but the thread is losing its way at the minute.

Posted 10 months ago #
MikeWhis

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Sorry guys.

Posted 10 months ago #
Geoff_K

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tcole1983 said:
Here we go...again not sure about merit here, but something...

http://snapsort.com/cameras/Nikon-D400

"Crop factor 1.6x " .. we are NOT Canon. Nikon is 1.5x (unless they are going to do something different this time around)

Posted 10 months ago #
iris chrome

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I agree. Someone should start a new thread dedicated to FX vs DX or equivalent f-stops..... huh? What's that you say? A 2 year old thread already exists on that topic? ;)

For what it's worth I think MikeWhis's original argument (FX is a better value than DX) deserves more credit than it's been given. However I do think one has to be careful when reporting/using equivalent f-stops. I think it's an uncommon practice of reporting DX f-stops but I do think it can be useful although it should be specified that equivalency only pertains to DoF and not exposure (or low light performance).

Posted 10 months ago #
bjrichus

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Geoff_K said:
"Crop factor 1.6x " .. we are NOT Canon. Nikon is 1.5x (unless they are going to do something different this time around)

and they also issue a "below average" thumbs down for not having image stabilization in the camera body.

Are they being paid by some other manufacturer or what?

I accuse.....

PS: How's that for my 777th post here?

Posted 10 months ago #
msmoto

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http://snapsort.com/cameras/Nikon-D400

Well....this info is simply what has been around since early June http://mansurovs.com/nikon-d400-announcement-this-fall

And the crop factor for the new D400 is reported as an actual 1.55 vs. 1.52 for the current cropped sensor Nikons. Strange how information would come out which seems inconsistent with the Nikon history, i.e., going with a new sized sensor. Also, how they can say the native ISO of 6400 is below average or inferior is beyond me as Canon's EOS 7 has only 6400 native ISO.

Sometimes these folks who write websites have no more knowledge than I do. They just wear pretty clothes and guess with a straight face, ha, ha, ha..... heck, in my world we call it pseudologia fantastica.

Posted 10 months ago #
tcole1983

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Had another link, but never mind...the source is Nikon Rumors...lol

Don't be harsh...I am just finding, not saying it is all true :)

Posted 10 months ago #
MikeWhis

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msmoto said:
http://snapsort.com/cameras/Nikon-D400

Well....this info is simply what has been around since early June http://mansurovs.com/nikon-d400-announcement-this-fall

And the crop factor for the new D400 is reported as an actual 1.55 vs. 1.52 for the current cropped sensor Nikons. Strange how information would come out which seems inconsistent with the Nikon history, i.e., going with a new sized sensor. Also, how they can say the native ISO of 6400 is below average or inferior is beyond me as Canon's EOS 7 has only 6400 native ISO.

Sometimes these folks who write websites have no more knowledge than I do. They just wear pretty clothes and guess with a straight face, ha, ha, ha..... heck, in my world we call it pseudologia fantastica.

Umm... D3200 has 1.55 crop factor too, and some other cameras. Recent cameras are having a crop factor at around 1.54. So it's not inconsistent. Moreover, they are not really changing the sensor size, 0.01 crop factor is almost nothing.

Posted 10 months ago #
TaoTeJared

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msmoto said:
And the crop factor for the new D400 is reported as an actual 1.55 vs. 1.52 for the current cropped sensor Nikons.

That is nothing new. If you look at the actual specs of all the sensors from Nikon and everyone else they vary just a bit. One problem is that people who take apart sensors pull out their calipers and try to measure the physical sensor. What they don't know is that there is usually a bit on the sides that actually are back end transistors or the like, or even just not used pixels. Not sure why but worth notating.

Posted 10 months ago #
msmoto

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@TaoTeJared ....as always, thank you. I keep learning from you folks in the midwest, ha,ha, ha...

Posted 10 months ago #
DaveyJ

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Hi to All on NR. Checking once again to see if the D400 announcement is any closer. Nikon eventually will solve this shortcoming but other than the D3200 (which does seem to have some really important upgrades from the D3100) but how about a really serious DX revamp??

Posted 10 months ago #
tsitalon1

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Bump

Posted 9 months ago #
efd123

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Likely doesn't mean anything but Amazon hasn't cancelled my pre-order for the D400 Magic Lantern guide book from April. I keep hoping they will fill the order soon

Dave

Posted 9 months ago #
msmoto

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Is it time to begin the bargaining with Nikon? ....LOL... like, if the D400 doesn't show its face in September at Photokina, Sony will sell an NEX 7....to me!

Posted 9 months ago #