haltedsisyphus

Ah yes. According to http://www.bobatkins.com/photography/digital/eos_digital_rebel_xt_vs_20d.html

 

"The Digital Rebel XT maximum sync voltage is also 250v, not 6v [...]. Canon have recently stated that the Digital Rebel XT does in fact share the 250v sync voltage."

 

Good news. I'll refrain from buying any kind of voltmeter until I find a need for one. Thanks Jim.

Thanks all for your kind support.

 

Mike: Yes, the Tamron does stay at f/8 if I hold down the DOF Preview button while unmounting the lens. And you're right - it can be quite satisfying to use what's at hand in new ways.

 

Mark: I'm glad that neglecting to reopen the aperture is unlikely to cause problems, and I'll try to keep the lens fit. If something goes wrong, I will be grateful for Tamron's 6-year warranty.

 

Bruce: I had heard that theory about stopping down the primary lens, and was curious whether there was more to that than a brighter image in the viewfinder. However, as you say, what works, works! I may start playing with different lighting soon; mini-lamps are pretty cheap.

Thanks Bob and Michael. I won't worry about it anymore, but still might pick up a cheap volt-meter next time I'm at a hardware store. It sounds like something that might come in handy someday anyway.

I recently received a 155A and AE-1 as a gift. I'd like to learn how to use the

manual flash on my Rebel XT rather than the AE-1 so I don't have to buy extra

film and develop several rolls of bad pictures during the learning process.

 

According to Jim Strutz, the voltage of the 155A is fine for EOS cameras.

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=002VKJ

http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=009Oce

 

But according to Kevin Bjorke's site, the 155A may be unsafe.

http://www.botzilla.com/photo/strobeVolts.html

 

I've tried the combo, and it works, but I have read that the bad effects of

mismatched voltage can be subtle at first and/or cumulative. Can anyone else

weigh in on the safety of this combination?

I am pleased with the results of coupling a Tamron 17-50mm f/2.8 to a mounted

Canon 70-200 f/4 L with a 67mm-67mm ring. With this setup, I've found that

stopping down the Canon lens reduces the image circle, whereas stopping down the

Tamron does not.

 

In light of this, I have been keeping the Canon lens at f/4 and have been using

the DOF Preview button to set the Tamron lens to f/8 before unmounting it. This

gives full-APS-C coverage from 135mm-200mm with a reasonable depth of field, and

without diffraction taking too much from image sharpness. At 200mm, this setup

also covers a full-frame sensor.

 

Examples here:

http://www.photo.net/photodb/folder?folder_id=720223

 

So, three questions:

 

1. Should I be concerned about the 430-gram Tamron lens hanging by its filter

threads every now and then? For long periods?

 

2. Should I be concerned about leaving the Tamron lens' aperture at f/8 for long

periods of time? Hours, days? (E.g., if I forget to remount the Tamron and

electronically reset the aperture.)

 

3. Any tips from people who have done similar things? From my calculations this

is about 12x magnification; the area covered on the APS-C sensor is about 1.9mm

x 1.3mm; working distance is about 3.5 cm. I'm using a cheap mini halogen

spotlight for strong, focused, constant lighting. Since I don't have tripod

rings or a focusing rail, I've just been setting the camera on a table and

brining subjects to it.

I bought mine new 8 months ago from a well-known, reputable dealer. According to the date code, it was manufactured in 2006.

 

If I give a mild shake to my lens while holding it close to the rear element I can hear a quiet, low-pitched rattle sound from the front. My guess is that something inside near the focus ring can move back and forth. (When I hold the lens near the front element and shake there is no sound.)

 

However, with 8 months of ample use the lens has not shown any problems with picture quality or focus speed/accuracy. Since problems in shooting never showed up, I figured that the sound was just part of how the lens was constructed.

 

I would be curious to know whether this is similar to what you experience. If so, let me know if you find out that this might actually a symptom of some problem (or indication of likely future problem), and what that problem is so I could send in the lens for a check-up before the warranty expires.

I am not sure if you noticed this when you read my post about the 70-300 IS portrait orientation problem back in January http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00EzHY but the issue with my lens was more obvious when it was turned 90 degrees clockwise than when it was turned 90 degrees counterclockwise. I imagine that for some copies of the lens, one of the two portait orientations might be awful and the other totally unproblematic.

 

I have no idea if your shooting style involves using each of the two portait orientations, but if you do and if you're not supporting the barrel intermittently, that might explain why the problem is not always present.

 

You may want to find out if the problem is less apparent in one of the two portait orientations. Then, when edge sharpness is important, remember to turn the camera that way instead of the other.

I have posted some information about that here: http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00EzHY&tag=

 

Depending on how important it is to you, you may want to test your lens and see if the looseness causes any loss in sharpness. I returned mine, but I would reconsider it if Canon announced a fix (or a longer warranty period).

Ah, but what -is- difference? Answer that and we will be halfway there.

Funny timing... I posted my experience with this problem about one minute after you did: http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=00EzHY&tag=

 

In my post is a link to a series of test pictures I took with my XT. Let me know if your problems are similar.

Disappointed, I am planning to return my new EF 70-300 IS USM f/4-5.6

tomorrow (as long as B&H cooperates) because it suffers from a

significant loss of quality when on its side (on my XT). I didn't see

much discussion on this forum of this problem before I decided on the

70-300 over the similarly priced f/4L, so I thought I'd mention it for

any who were not yet aware and who were making a similar decision.

 

At dpreview, Peter_M discusses the problem here:

http://forums.dpreview.com/forums/read.asp?forum=1029&message=16623268

and the cause of the problem here:

http://forums.dpreview.com/forums/read.asp?forum=1029&message=16712560

 

To summarize the info in the links: the extending portion of the lens

is not held securely in place (mine can only wobble 1-2mm, but that

seems enough to cause visible problems in the field); when in

landscape mode the lens groups are aligned well and there are no

problems; when in portrait mode the lens groups are slightly askew,

causing optical issues especially at the edges. The problem can be

alleviated by pushing the extending portion of the lens back to

center, which provides strong evidence that the wobbly lens barrel is

the problem.

 

My own tests had comparable results:

http://www.photo.net/photo/4054677

(Boring test photo details: IS off, tripod mounted, mirror lock up,

cable release, 300mm, Manual mode, ISO 100, f/8, 0.6", top=0',

middle=270', bottom=90')

 

These 100% crops are taken from the side of each picture, at equal

distance and orientation from center. As discussed at dpreview, I

found that the loss in sharpness becomes greater at greater distances

from center. That being said, I found a reduction in center quality

as well. I ran the same test at 200mm and found a similar pattern of

quality loss.

 

I don't think I'm crazy to consider this a noteworthy problem. I am

pessimistic about Canon acknowledging or fixing it, which is why I am

returning the lens. I can't say how prevalent the problem is, but it

seems as though several people are experiencing it. Given the

construction of the 70-300 and its tendency towards wobbliness, I

wouldn't be surprised if the problem started to creep up on more

people over time.

 

Honestly, kudos to Canon for putting some efficient glass and IS in a

moderately priced telephoto zoom. I would have kept the lens if I

hadn't felt that it would have limited my photography. This post is

not intended to scare all people away from the lens, but I thought the

problem should be made known.

Long time reader, first time poster. XT owner for 6 months at 19000

shots (I�m new to photography and have embraced trial & error).

Current lenses: 18-55mm, 50mm 1.8/II, Peleng 8mm. Since purchasing

the XT, I have been planning to get the f/4L around this time. Like

many, I�m now torn between the L and the new IS.

 

The decision is difficult for me due to my inexperience. My lens

purchases don�t so much revolve around what I shoot; instead, my

shooting depends upon which lens I own. (e.g. I only started shooting

in low light after getting the 50mm, but I enjoy it). I lack any

defined objective and I�m still learning, but I know a good telephoto

zoom will round out my lens collection. I�m on a tight budget and

hope to have this purchase end my buying for quite a while.

 

So here�s the twist. I�ve come to enjoy macro shooting by holding a

reversed 18-55mm at 18mm to the camera body (usually stopped down to

f/8 or so using the DOF preview button). This has allowed for some

pretty good, though inconvenient and dust-speckled, shots at a

magnification somewhere around 3.66x. I am hoping to use my telephoto

zoom as a more convenient 1:1 macro lens with either the 6T (for the L

with a step-down ring) or the 500D (for the new IS).

 

And finally, my questions:

 

1) Given the popularity of the new IS, is the price likely to go below

its current $550 (after rebate) anytime soon? Since I�m new to the

game, I�m not familiar with Canon�s typical pricing schedules.

 

2) Will the pop-up flash do me any good in lighting my macro subjects

for both of these lens combinations?

 

3) Even if the 62mm 6T doesn�t vignette on the L with the 1.6 crop

sensor, is there curvature to the 62mm filter size 6T and the 67mm

filter size L that will make for a troubled optical marriage, perhaps

most noticeable at the borders?

 

4) B&H has shown a backorder for the 6T for a while. Will one be hard

to find?

 

5) Are there any reports on how the new IS performs with the 500D?

Any hunches?

 

6) Will the new IS + 500D combo be significantly better for handheld

macro work, due to the IS? Since the XT�s flash-sync is 1/200, will

there tend to be more 1:1 keepers at 300mm with IS than at 200mm without?

 

Important note: Although most of my questions relate to macro uses, it

is only a side consideration for my lens purchase. The 100 macro has

been tempting, but as of now I think one of the zooms will round off

my beginner�s lens collection better. I have weighed the other

factors of the L and the new IS, so no need to rehash those on this

thread, but these six questions remain for my decision.

 

Thanks so much to those willing to help with any of the questions on

this marathon of a post.