Another way to focus your SLR camera

cataclysm · Post by **cataclysm** » Wed Oct 03, 2007 10:54 pm

Hi, check this out! A new gadget for focusing digital camera.
http://www.kwtelescope.com/FotoSharp_page.htm

vhuang168 · Post by **vhuang168** » Thu Oct 04, 2007 12:06 am

Interesting... wonder how it works. It seems to use the cameras focus sensors but doesn't say how.

Vincent

Post by **weixing** » Thu Oct 04, 2007 12:23 am

Hi,

Interesting... wonder how it works. It seems to use the cameras focus sensors but doesn't say how.

I think the adapter just activate the lens mounting pins to "fool" the DSLR and thought that the "lens" is in manual focus mode.

Anyway, this is very interesting and may be quite useful... just wonder does this adapter got the same length as a T-Ring?? If the length is longer, than coma corrector may not work properly.

Have a nice day.

opteron · Post by **opteron** » Thu Oct 04, 2007 12:36 am

hmm i assume there is a lens element inside to adjust focus ?

anyway objects that far would already require infinity focus ?

i cant speak for canon, but nikons have a AF switch on the body right? just off it and u have snap at any focus distance.

Post by **weixing** » Thu Oct 04, 2007 12:54 am

Hi,

hmm i assume there is a lens element inside to adjust focus ?

I think that just an adapter than connect to DSLR lens mount and provide a Female T-thread for the telescope to connected to. You adjust the focus using the telescope focuser.

anyway objects that far would already require infinity focus ?

Telescope don't have infinity marking as they are not design for SLR use only.

i cant speak for canon, but nikons have a AF switch on the body right? just off it and u have snap at any focus distance.

I think Canon do not have the auto/manual focus selector switch on it's body... it is on the Lens itself, so when you switch to manual focus mode on the lens, the focus confirmation light or beep (if enabled) will be activated when the lens achieve focus. But when you connected to telescope using T-Ring, the focus confirmation light or beep (if enabled) won't be activated even you achieve focus.

Anyway, will the Nikon focus indicator light still activate if you achieve focus, but not using a lens... such as through a telescope via T-Ring??

Have a nice day.

opteron · Post by **opteron** » Thu Oct 04, 2007 8:29 am

weixing wrote:Hi,

Telescope don't have infinity marking as they are not design for SLR use only.
I think Canon do not have the auto/manual focus selector switch on it's body... it is on the Lens itself, so when you switch to manual focus mode on the lens, the focus confirmation light or beep (if enabled) will be activated when the lens achieve focus. But when you connected to telescope using T-Ring, the focus confirmation light or beep (if enabled) won't be activated even you achieve focus.

Anyway, will the Nikon focus indicator light still activate if you achieve focus, but not using a lens... such as through a telescope via T-Ring??

Have a nice day.

i see.

what i mean re:infinity focus is that, even viewing of DSO, moon thru human eyes, we already focus to infinity arent we?

i am not familiar with scopes so i never saw the focusing ring on 1 but shldnt it be focused to infinity already?

assuming my camera's focus works for all DSLRs, nikon's aperture priority mode must detect the lens. meaning to say, the lens must have CPU contacts (af lens). to use any manual lens (w/o cpu contacts), i must switch to Manual mode which basically switches off focusing and metering.

in Manual mode, whether u are in focus or not, it will still take a picture.

thanks for the insight for canon cameras

kayheem · Post by **kayheem** » Thu Oct 04, 2007 8:45 am

The gadget cataclysm linked to is something similar to this item in ClubSnap:

http://forum.clubsnap.org/showpost.php? ... ostcount=1

The only difference is that the first item comes with the adaptor all attached. The CS version is just a chip which you need to stick onto the T-ring. They also sell adaptors with chips for other mounts e.g. Nikon or Olympus to EOS mount:

http://www.tagotech.com/index_files/Page377.htm

I am not affliated with the vendor, I am just a happy customer :-)

Kay Heem

wucheeyiun · Post by **wucheeyiun** » Thu Oct 04, 2007 11:33 am

weixing wrote:Hi,
hmm i assume there is a lens element inside to adjust focus ?
I think that just an adapter than connect to DSLR lens mount and provide a Female T-thread for the telescope to connected to. You adjust the focus using the telescope focuser.

anyway objects that far would already require infinity focus ?
Telescope don't have infinity marking as they are not design for SLR use only.

i cant speak for canon, but nikons have a AF switch on the body right? just off it and u have snap at any focus distance.
I think Canon do not have the auto/manual focus selector switch on it's body... it is on the Lens itself, so when you switch to manual focus mode on the lens, the focus confirmation light or beep (if enabled) will be activated when the lens achieve focus. But when you connected to telescope using T-Ring, the focus confirmation light or beep (if enabled) won't be activated even you achieve focus.

Anyway, will the Nikon focus indicator light still activate if you achieve focus, but not using a lens... such as through a telescope via T-Ring??

Have a nice day.

I have tried focusing with the mewlon with t-adapter ( no cpu contact ) on d200, and the focusing indicator appeared to work, it flickers as it getting focus. I will try again with the mewlon reducer when it arrives...

Post by **weixing** » Thu Oct 04, 2007 12:10 pm

Hi,

have tried focusing with the mewlon with t-adapter ( no cpu contact ) on d200, and the focusing indicator appeared to work, it flickers as it getting focus. I will try again with the mewlon reducer when it arrives..

According to the link kayheem provide, Nikon and Canon DSLR react opposite when a non-lens is attached to it:
1) Canon DSLR: metering still function (in manual and aperture priority mode) but AF indicator is disabled.
2) Nikon DSLR: AF indicator works but metering don't. (Unless you are taking lunar and planets, you don't need the metering).

Have a nice day.

wucheeyiun · Post by **wucheeyiun** » Thu Oct 04, 2007 12:46 pm

weixing wrote:Hi,
have tried focusing with the mewlon with t-adapter ( no cpu contact ) on d200, and the focusing indicator appeared to work, it flickers as it getting focus. I will try again with the mewlon reducer when it arrives..
According to the link kayheem provide, Nikon and Canon DSLR react opposite when a non-lens is attached to it:
1) Canon DSLR: metering still function (in manual and aperture priority mode) but AF indicator is disabled.
2) Nikon DSLR: AF indicator works but metering don't. (Unless you are taking lunar and planets, you don't need the metering).

Have a nice day.

Infact for d200 metering can still works with non cpu lens or any telescope because it is TTL metering