I'm reasonably experienced with the good 'ol SLR camera (and DSLR) but there's one thing that is bugging me more and more with my Canon. Not having the lens stop at infinity.
I understand why this is not possible with the new lenses - temperature variations having an effect on the modern fancy optics, but, really - it's a pain!
I just got my prints back of my McNaught images. Most are perfect but there's one shot (the best of course) which at 80cm x 50cm print size it is obvious when viewing up close that the stars are slightly out of focus. Disappointing to put it mildly!
For normal astro photography I focus using DSLRFocus - no problem there.
For most of my McNaught images I zoomed in on Venus, focused, then zoomed out and re-framed for the comet (my lenses are parfocal across all zoom range).
But on this one occasion Venus had set, and being my 17-40mm lens, focusing on any of the bright stars that were visible was very hard - they were so small.
I would often take a shot, view it, zoom in and check the focus - time consuming and I didn't have time on this occasion.
I realised then also how small the image physically is in my 350D vs my old Pentax SP1000, not helping the situation. (I wonder if the more expensive Canon's have larger physical image size to view?)
Any advice for these situations where you don't have a bright Venus or Sirius to focus on, and are not hooked up to a computer to focus using DSLR Focus??
It's really got me now that it's ruined the chance of me printing one of my shots to 80cm
hey roger, i have the same problem at times,
i have found that an eyepiece held up to the viewfinder works.
as well as a magnifing glass
also the varimagni helps alot
Why cant you use DSLR focus for the camera alone. After all mike unsold demonstrates his version in images plus on one of his tutorials using a camera alone?
regards philip
Why cant you use DSLR focus for the camera alone. After all mike unsold demonstrates his version in images plus on one of his tutorials using a camera alone?
regards philip
I'm talking about situations where I don't have the camera connected to a computer, so am not running DSLR Focus. Case in point being recent photography for the comet where I simply had my camera + tripod.
I'm talking about situations where I don't have the camera connected to a computer, so am not running DSLR Focus. Case in point being recent photography for the comet where I simply had my camera + tripod.
Have I misunderstood what you have said perhaps?
I was assuming you went with the intention of photographing the comet .If so laptop +dsusb would be no great effort if you want perfect focus for that one great image. I find that for stars in the camera viewfinder of atypical DSLR like a canon 350D , a right angle focus magnifier 2.5x helps but is no guarantee of focus as the texture of the screen limits your focussing accuracy. in some older film SLR's you could replace the focussing screenfor one finer.The stilleto focusser mentioned in a previous post would need a fine texture screen to do it justice!
philip
Last edited by 5ash; 01-02-2007 at 02:56 PM.
Reason: additional info
Hi Guys, i'll just put my two bob's worth in here.
I use a Canon 5D with various lenses, ranging from F2.0 to F4.0 and i believe at F5.6 this will work as well, and it dose work very well, for me.
Although i do have a Canon angle finder, i only use this if the F Ratio is beyond F4.0-5.6.
This is what i do, and i'll show the example using my Canon 300mm F/4.0
Set the camera so that only the center red square activates when you press the remote button half way down, it will also beep, when focused.
Mount the camera as normal on the mount with lens, and remote connected, and manually move the mount.
Put the lens on auto focus, have the expo set on bulb, find a star close to where you intend to image, and center it on the red square, which will eluminate each time you press the shutter half way down, once you hear the beep, beep you are focused.
Now switch the lens back to manual, (most important, i forget sometimes too). and image away, works every time for me, and as it gets colder you can re-focus, just repeat the procedure.
You dont need a computer to focus, admittly it can be a little fiddly at times, but once you get the hang of it it comes natural.
Hi Roger,
When I got my D200 last year, one of my first impressions of it was that the viewfinder was tiny. It was disappointing and annoying after reading reviews and specifications sheets saying that it had a huge viewfinder with 0.94x magnification at 95% coverage. When I looked at the mirror it became obvious why the viewfinder was smaller compared to the 35mm viewfinder I'm used to (see the pic below with film on the left, digital on the right). Smaller sensor (16x24mm compared to 24x36 film) means smaller mirror which leaves a tiny image in the viewfinder! I ordered a 1.17x magnifying eyepiece for it yesterday and it appears that it would also work on your 350D according to one review here http://www.amazon.com/Nikon-DK-21M-M...&s=electronics (note the picture is incorrect on this link!)
Something like that might help, but I always check the focus by taking a test shot (AF on a bright star is usually spot on) and then zoom in to actual pixel size on the LCD to check fucus.
I also too find this feature of modern lenses to be very astro-unfriendly roger, what a waste of precious imaging/viewing time! what bugs me, is how the heck do you put a kendricks dew heater strap on the lens and stop it from pulling/tugging on it and changing focus once achieved - can ya lock the focus in manual? with the old film primes, we just position the kendricks so it pulling the focus hard up against infinty, if anywhere at all - hard right or left as you know - how the heck is this achievable with the dslr stuff? i mean even the primes have multiple infinities!
Very interesting and useful replies! This is turning out to be quite informative.
Philip - you are right, it wouldn't be so hard to have the laptop there. But there are 3 reasons I can think of why this didn't suit my comet work:
1) I wanted to move around quite a bit, framing the comet with different foreground objects
2) Being fixed on a normal tripod, locking on to a star with DSLR Focus might have been a problem, with it drifting out of the FOV
3) I was often at locations where there were 50 - 200 other people also observing the comet, so the less expensive gear to keep an eye on the better. This also limited working space.
Jonathan - that looks like exactly the kind of thing that might help. I'll be interested to hear what you think of it when it arrives. Quite affordable too.
fringe dweller - ahh, something else I hadn't thought of. I do have to be particularly careful not to adjust the focus after I've focused on a star, when moving the camera around. It would really help if I could lock/disengage the focusing ring... interesting idea!
And they are probably not too good for astrophotos. Here is a quote from Jerry Lodriguss' e-book:
"This is enough to work if you are careful and have good eyes and experience, but these finders are dim and your eye has to be exactly centered in the "sweet spot" of the field of view of the finder to work at all. They are certainly too dim to find, frame and focus a deep-sky object. You can move the scope to a bright star to focus, but when you move it back to the object, you will not be able to see it through the camera on the main scope. You will either have to center it with an auxiliary guide scope, or find it with manual or digital setting circles, or computerized Go To software."
What I sometimes do is use the autofocus to focus on a distant object during daylight, then switch to manual (so it doesn't try focussing when you shoot) and then don't touch the lens for the rest of the night.
