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04-29-2018, 08:30 PM   #1
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Canon EOS Rebel T5 compatibly incompatible with Sigma 70~300mm 1:4~5.6 APO Macro Lens

Greetings,

I have a Canon EOS Rebel T5 which is in excellent condition. I mated it up with a recently acquired Sigma 70~300mm 1:4~5.6mm APO Macro Lens. Please bare with me because I am trying to describe my problem. The lens fits perfectly, no problem there. I should also mention that I have a Sunpak external flash, made exclusively for my T5. It also is in excellent condition. When practicing to learn how these two guys get along, I noticed something very peculiar. Here are my settings: 1/125s, F/4.0, ISO 100 and shooting in Manual Mode. I should mention that I have never had a problem with this flash, in fact I like it better than some of the speedlights that Canon offers.

Okay, at these settings, my photographs came out a little underexposed, again using the external flash. Now, here is the weird part. The more I shut down the lens, the more overexposed the photographs turned out. I increased the number for the f/stop setting all the way down to f/25 and again, grossly overexposed. Then I decided to increase the shutter speed to 1/800s, and left the other settings alone. When looking through the viewfinder, I noticed the shutter speed automatically adjusted itself to 1/200s and at this speed, the flash would not flash. I reset the shutter speed to 1/160s, the flash worked but the image was horrible. I then decided that perhaps I was too close to the subject and I then moved farther back. There was a little change, but nothing to write home about. The flash unit does have a diffuser which I did use and it turned out alright. The question is of course, why are the exposure settings changed prior to taking the photo? I can upload the photos here which will show the EXIF data. I do like the images I get with the Sigma lens. The auto-focus is very accurate, however it is slow so just a minor inconvenience. Thanks for the help. The batteries are all fully charged and I did clean all the contacts. Also, why are the lens settings working erroneously?

Tony


Last edited by Tonytee; 04-29-2018 at 08:44 PM. Reason: Additional Information.
04-29-2018, 08:46 PM   #2
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Hi Tony
Are you sure the camera is incompatible with the lens? It sounds more like you have some kind of flash problem.
Regards,
Mark
04-29-2018, 08:54 PM   #3
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QuoteOriginally posted by MarkJerling Quote
Hi Tony
Are you sure the camera is incompatible with the lens? It sounds more like you have some kind of flash problem.
Regards,
Mark
Right. How does the lens behave with non-flash shots?

There is also a very good reason that when you set 1/800 sec shutter speed the camera automatically resets to 1/200 sec with the flash because that is the camera's flash sync limit. Your flash and camera would have to have high-speed flash capability and settings to go beyond the native flash sync.

As to the other problems, either the flash metering with external fish units in your camera is screwed up, or the flash unit is at fault.

Last edited by mikesbike; 04-29-2018 at 09:02 PM.
04-29-2018, 09:25 PM   #4
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QuoteOriginally posted by MarkJerling Quote
Hi Tony
Are you sure the camera is incompatible with the lens? It sounds more like you have some kind of flash problem.
Regards,
Mark
Hi Mark,

I removed the Sigma lens and replaced it with the Canon EF-S 55~250 IS, II and the flash and camera worked flawlessly. The Canon and Sigma work very well in broad daylight with no flash. So you are thinking that there is a potential problem between the Sigma lens and Sunpak flash. The listing that Sigma put together for this lens, does include all of Canon's EOS Rebel T bodies. I can work with the Sigma lens as long as I open it up to the maximum with the flash, although there is the potential for grossly underexposed images. I haven't done anything in the way of adjusting the ISO setting and that may turn up something interesting. I do have a Nikon Spdlight and an Olympus Spdlight and will see what happens when using them with the Sigma lens. Will report shortly.

Tony

---------- Post added 04-29-18 at 10:01 PM ----------

With the exception of two minor adjustments on the Nikon Spdlight sitting on the Canon camera with the Sigma lens, everything turned out much better than expected. Now here is a different story with my Olympus Spdlight. With the shutter speed at 1/125s and lens setting at f/25 the image came out quite nicely. However, with the shutter speed at 1/125s and the lens setting at F4.0, the image duplicated the first one. It does appear as if the lens is in control of the Sunpak flash. After all this, it does boil down to the fact that I rarely do any low light or night photography, however, it is good to know what works best with what apparatus.

Thanks very much for all the help.

Tony

04-30-2018, 02:42 AM   #5
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I'm not familiar with the lens/body combo, but you can't set your shutter speed to faster than your flash sync speed which is 1/200 second. My guess is that you probably need to use the flash in manual mode with that lens and just turn down the power.
04-30-2018, 01:27 PM   #6
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QuoteOriginally posted by Rondec Quote
I'm not familiar with the lens/body combo, but you can't set your shutter speed to faster than your flash sync speed which is 1/200 second. My guess is that you probably need to use the flash in manual mode with that lens and just turn down the power.
Hi Rondec,

The Sunpak RD2000 flash does not have different modes. It has only one mode. I am able to increase/decrease the intensity of the flash by the EV buttons just above the mounting set up. The flash head is adjustable for bouncing off walls and ceilings. This Sunpak flash was made exclusively for Canon cameras. I can verify that because I once tried to use it on my Pentax k-50 and thought I managed to destroy the flash. Fortunately it was just fine. Thanks for commenting.

Tony
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