Effect of cropping on a teleconverter

trolley

I have a cheap 2X teleconverter. What is it's effect on the focal length when you switch an FX camera to DX crop mode?
For instance, a 300mm lens with a 1.5X crop would be 450mm. With a 2x converter, do you get 900mm (2x450)?
It seems a bit like a free lunch. Or does degradation mean it's unusable anyway?

scoobysmak

The file the camera would create is the equivalent field of view of 900mm but you lost a majority of your pixels due to switching to DX mode and usually a 2x TC does affect the image quality. You magnified the issue of the image quality by "zooming in" using the DX mode. There are a few exceptions that a 2x TC doesn't affect the image that bad but usually these are with Nikon Pro lenses like a 400mm f 2.8 or similar.

I prefer to just crop the image how I see fit Vs using DX mode, gives me more flexibility to crop what I want in my photo than a split second decision that might have something "weird" I don't like later.

trolley

Since I am that way inclined, when the camera & lens arrive I'm going to take the same picture with & without the converter on & with & without crop & see what I get.
I'm thinking that at full frame, if you enlarge part of the area it may be better than DX mode.
But I won't pre-empt the results ;;)

sevencrossing

what camera are you using?
As far as IQ is concerned, there is no difference between putting in Dx mode and cropping in post
a cheap teleconverter on a modern DSLR is more likely to degrade rather than improve IQ

trolley

It'll be on a D800

Ironheart

@trolly, the free lunch, or lack thereof, comes in the form of light. A 2x teleconverter chews up two stops of light, so an f/2 lens becomes an f/4, an f/2.8 becomes a f/5.6. An f/4 becomes an almost useless f/8 and an f/5.6 becomes a completely useless f/11. The reason it is useless is that a) the camera can't autofocus b) you can't either 'cause you can't see jack s#%t. Don't even bother with a variable zoom. A fixed prime, maybe. If it is a 3rd party TC, you will also need to worry about physical interference with the back element on the lens; if they whack into each other you could get scratches or worse.

sevencrossing

It'll be on a D800

You will almost certainly be better off cropping in post
as Ironheart says you will also need to worry about physical interference with the back element on the lens

heartyfisher

It'll be on a D800

Whats the lense ?

Photobug

When I cropped a few of the Bald Eagle pictures taken on the D750 the IQ was impressive. Agree with severncrossing on cropping in post.

trolley

Lens will be a Nikkor 300 f4. I currently use a Sigma 150-500mm on a D200

sevencrossing

I believe there are 3 versions of the lens

The 300mm f/4 IF-ED (1987 to 2000)
The 300mm f/4D ED IF AF-S ( 2000 to 2014)
and the latest AF-S NIKKOR 300mm f/4E PF ED VR


I have not used any of them but all get good reviews and should give excellent results with a D800 ( which I do have )

They seem to get good reviews with a Nikon 1.4 converter

I feel adding a third party 2x converter will not give you good results

Msmoto

The operative word is "cheap". A question regarding unknowns is only answered by reviewing the results of its use. My suggestion would be to take a few images, make certain no other confounding factors are present, i.e., shoot in adequate light so as to be able to stop down a few stops, have a high shutter speed or on sticks, and make certain the exposure is correct, then post a full size image on Flickr and give us a link.

Then, and only then can one properly evaluate the image quality.

Photobug

I believe there are 3 versions of the lens

The 300mm f/4 IF-ED (1987 to 2000)
The 300mm f/4D ED IF AF-S ( 2000 to 2014)
and the latest AF-S NIKKOR 300mm f/4E PF ED VR

Yes you are correct Nikon made three 300 F4 lens. For the record, Nikon has made SIX 300mm lens; the other there at F4.5. Here is the link to a comparison table for all six lens.
http://www.kenrockwell.com/nikon/comparisons/300mm-f4.htm

This is an example where KR's web site is good. He loves to put these comparison tables together.